I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem
is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a
couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get
rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem
is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a
couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get
rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem
is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a
couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get
rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
I'm thinking about building a biggish rackmount dummy load box. Itwould simulate series resistance and inductance. Part of the problemis that it will need to dump a lot of heat.We are using copper CPU coolers on PC boards, which are great up to acoupleof hundred watts, but I'd like to do a kilowatt or two.https://highlandtechnology.com/Product/P945It would take a heap of expensive extruded heat sinks and fans to getrid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degCtemp rise.A small
john larkin <jl@glen--canyon.com> Wrote in message:racouple of hundred watts, but I'd like to do a kilowatt or two.https://highlandtechnology.com/Product/P945It would take a heap of expensive extruded heat sinks and fans to getrid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degCtemp rise.
I'm thinking about building a biggish rackmount dummy load box. Itwould simulate series resistance and inductance. Part of the problemis that it will need to dump a lot of heat.We are using copper CPU coolers on PC boards, which are great up to
There are those Edison base ceramic heaters . Maybe you can cobble
up something with those.
Cheers
I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem
is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a
couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get
rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem
is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a
couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get
rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem
is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a
couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get
rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
john larkin <jl@glen--canyon.com> wrote:
I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem
is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a
couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get
rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
If you are using elements at near red heat, remember you need to keep
the radiant heat away from the outer walls of the cabinet. Reflectors
just throw the problem elsewhere and eventually will tarnish, the best
system is several spaced blackened steel baffle plates with vertical air >passages between them (visual black is not always IR black).
If you need a rapidly-controllable load, valves can dissipate energy at
a much higher temperature than transistors, so they might be worth >considering.
john larkin <jl@glen--canyon.com> wrote:
I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem
is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a
couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get
rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
If you are using elements at near red heat, remember you need to keep
the radiant heat away from the outer walls of the cabinet. Reflectors
just throw the problem elsewhere and eventually will tarnish, the best
system is several spaced blackened steel baffle plates with vertical air >passages between them (visual black is not always IR black).
If you need a rapidly-controllable load, valves can dissipate energy at
a much higher temperature than transistors, so they might be worth >considering.
On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <jl@glen--canyon.com> wrote:
I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem
is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a
couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get
rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
If you are using elements at near red heat, remember you need to keep
the radiant heat away from the outer walls of the cabinet. Reflectors
just throw the problem elsewhere and eventually will tarnish, the best >>system is several spaced blackened steel baffle plates with vertical air >>passages between them (visual black is not always IR black).
If you need a rapidly-controllable load, valves can dissipate energy at
a much higher temperature than transistors, so they might be worth >>considering.
https://ve3ute.ca/2000a.html
RL
On Wed, 04 Dec 2024 13:29:03 -0800, john larkin <jl@glen--canyon.com>
wrote:
I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem
is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a >>couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get
rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
HVAC heater elements are available, premounted in ductwork.
Typical value 10R xKw. Tap, cut or series/parallel to your heart's
content.
The components to build similar structures, ceramic insulators,
and terminals and coiled resistance wire (of selected tempco)
are all available off the shelf. Punch your own metalwork.
RL
On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <jl@glen--canyon.com> wrote:
I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem
is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a
couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get
rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
If you are using elements at near red heat, remember you need to keep
the radiant heat away from the outer walls of the cabinet. Reflectors
just throw the problem elsewhere and eventually will tarnish, the best >system is several spaced blackened steel baffle plates with vertical air >passages between them (visual black is not always IR black).
Seems to me that black baffles will absorb IR and get hot, so devolve
to air-cooled heat sinks.
The solution to the IR problem is to reduce the element temperature
so's to shift the dissipation from radiation to air heat transfer. I
think the math on that is good.
If you need a rapidly-controllable load, valves can dissipate energy at
a much higher temperature than transistors, so they might be worth >considering.
Probably not practical. Tubes are big and full of expensive vacuum
which doesn't conduct heat well. May as well use some giant tubular incandescent lamp which has the same glass and heater as a big tube.
Most are filled with a gas that conducts heat better than vacuum, so
would bet more air cooling from the glass.
Tubes radiate heat from the plate, so I'd need to step up my source to
high voltage.
On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <jl@glen--canyon.com> wrote:
I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem
is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a
couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get
rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
If you are using elements at near red heat, remember you need to keep
the radiant heat away from the outer walls of the cabinet. Reflectors
just throw the problem elsewhere and eventually will tarnish, the best >system is several spaced blackened steel baffle plates with vertical air >passages between them (visual black is not always IR black).
If you need a rapidly-controllable load, valves can dissipate energy at
a much higher temperature than transistors, so they might be worth >considering.
https://ve3ute.ca/2000a.html
On Thu, 05 Dec 2024 08:01:01 -0500, legg <legg@nospam.magma.ca> wrote:...
If I'm going to use a finned circular heat sink, why put a tube
inside? Resistors would be cheaper.
But as noted, it would be hard to dump a kilowatt or two into a finned
heat sink. Well, unless I let its surface temp approach incandescence.
I'm considering using a class-D amplifier that can sometimes be
back-driven as a dummy load, in which case it pumps up its own power
supply, normally something like 70 volts maybe. I need to synthesize
the equivalent of a two kilowatt, 75 volt zener.
We're just brainstorming a product at this point, toying with goofy
ideas. With the right people, that is as Phil says, the most fun you
can have standing up.
On Wed, 4 Dec 2024 18:53:31 -0500 (EST), Martin Rid<martin_riddle@verison.net> wrote:>john larkin <jl@glen--canyon.com> Wrote in message:r>> I'm thinking about building a biggish rackmount dummy load box. Itwould simulate series resistance andinductance. Part of the problemis that it will need to dump a lot of heat.We are using copper CPU coolers on PC boards, which are great up to acouple of hundred watts, but I'd like to do a kilowatt or two.https://highlandtechnology.com/Product/P945It
On 05/12/2024 22:03, Liz Tuddenham wrote:
john larkin <JL@gct.com> wrote:
On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <jl@glen--canyon.com> wrote:
I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem >>>> is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a >>>> couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get >>>> rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC >>>> temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
If you are using elements at near red heat, remember you need to keep
the radiant heat away from the outer walls of the cabinet. Reflectors >>> just throw the problem elsewhere and eventually will tarnish, the best >>> system is several spaced blackened steel baffle plates with vertical air >>> passages between them (visual black is not always IR black).
Seems to me that black baffles will absorb IR and get hot, so devolve
to air-cooled heat sinks.
Yes, all the energy is eventually going to finish up heating the air,
the only question is the pathway it takes. One way to avoid that would
be to construct a massive infra-red searchlight beaming the energy away from the earth - or a broadcast transmitter beaming upwards.
To dump heat into the air, you either have to have something very conductive with a large surface area or you need another way of
spreading the energy across a suface, such as heat radiation. A big
sheet of thin, blackened steel plate for heating by radiation is a lot cheaper than a thick die-cast aluminium lump with fins for heating by conduction.
The economics of mechanically-forced air cooling are better than
convection unless you are able to use a tall 'chimney', so that the
energy of the waste heat is used to generate the draught.
A full sized rack cabinet could be remarkably similar to a chimney
if it had baffles in the right places.
John R Walliker <jrwalliker@gmail.com> wrote:
On 05/12/2024 22:03, Liz Tuddenham wrote:
john larkin <JL@gct.com> wrote:
On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <jl@glen--canyon.com> wrote:
I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem
is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a >> >>>> couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get >> >>>> rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC >> >>>> temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
If you are using elements at near red heat, remember you need to keep
the radiant heat away from the outer walls of the cabinet. Reflectors >> >>> just throw the problem elsewhere and eventually will tarnish, the best >> >>> system is several spaced blackened steel baffle plates with vertical air >> >>> passages between them (visual black is not always IR black).
Seems to me that black baffles will absorb IR and get hot, so devolve
to air-cooled heat sinks.
Yes, all the energy is eventually going to finish up heating the air,
the only question is the pathway it takes. One way to avoid that would
be to construct a massive infra-red searchlight beaming the energy away
from the earth - or a broadcast transmitter beaming upwards.
To dump heat into the air, you either have to have something very
conductive with a large surface area or you need another way of
spreading the energy across a suface, such as heat radiation. A big
sheet of thin, blackened steel plate for heating by radiation is a lot
cheaper than a thick die-cast aluminium lump with fins for heating by
conduction.
The economics of mechanically-forced air cooling are better than
convection unless you are able to use a tall 'chimney', so that the
energy of the waste heat is used to generate the draught.
A full sized rack cabinet could be remarkably similar to a chimney
if it had baffles in the right places.
Yes, as long as the ceiling of the room isn't lined with polystyrene
tiles. It might not be very good for the air conditioning system in the >building where this is installed, regardless of which dissipation method
is used.
In the days of germainium transistors, one firm used to make cabinets
with a 'clerestory' roof, like an upturned tray suppoted on spacing
pillars above the ventilation holes in the roof proper. This allowed
the heated air to flow out under the lip in case some idiot put the >instruction manual on the top of the cabinet.
Another possibility, especially if there aren't going to be many of
these on sale and the installation will be done by the firm that makes
them, is to make a hole in the wall and stick some stainless-steel
boiler flues up the outside of the building. Even better, in an old >building. use a redundant fireplace and put the contol box in a
decorative housing on the mantlepiece.
On Wed, 04 Dec 2024 13:29:03 -0800, john larkin <jl@glen--canyon.com>
wrote:
I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem
is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a
couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get
rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
Yes. A toaster element: Nichrome wire woven onto a mica card in a
perforated metal box.
Already packaged, one can get ballast resistors for high-power VFDs
used to power machine tools. The ballast resistor absorbs the energy
stored in a large chuck spinning fast, when it's time to come to a
stop quickly without over-voltage tripping the VFD.
.<https://www.automationdirect.com/adc/shopping/catalog/drives_-a-_soft_starters/ac_variable_frequency_drives_(vfd)/braking_units_-a-_resistors/br-n1-800w18p0>
Joe Gwinn
On Fri, 6 Dec 2024 08:29:33 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
John R Walliker <jrwalliker@gmail.com> wrote:
On 05/12/2024 22:03, Liz Tuddenham wrote:
john larkin <JL@gct.com> wrote:
On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <jl@glen--canyon.com> wrote:
I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem >> >>>> is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a >> >>>> couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get >> >>>> rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
If you are using elements at near red heat, remember you need to
keep the radiant heat away from the outer walls of the cabinet.
Reflectors just throw the problem elsewhere and eventually will
tarnish, the best system is several spaced blackened steel baffle
plates with vertical air passages between them (visual black is not
always IR black).
Seems to me that black baffles will absorb IR and get hot, so devolve >> >> to air-cooled heat sinks.
Yes, all the energy is eventually going to finish up heating the air,
the only question is the pathway it takes. One way to avoid that would >> > be to construct a massive infra-red searchlight beaming the energy away >> > from the earth - or a broadcast transmitter beaming upwards.
To dump heat into the air, you either have to have something very
conductive with a large surface area or you need another way of
spreading the energy across a suface, such as heat radiation. A big
sheet of thin, blackened steel plate for heating by radiation is a lot >> > cheaper than a thick die-cast aluminium lump with fins for heating by
conduction.
The economics of mechanically-forced air cooling are better than
convection unless you are able to use a tall 'chimney', so that the
energy of the waste heat is used to generate the draught.
A full sized rack cabinet could be remarkably similar to a chimney
if it had baffles in the right places.
Yes, as long as the ceiling of the room isn't lined with polystyrene
tiles. It might not be very good for the air conditioning system in the >building where this is installed, regardless of which dissipation method
is used.
In the days of germainium transistors, one firm used to make cabinets
with a 'clerestory' roof, like an upturned tray suppoted on spacing
pillars above the ventilation holes in the roof proper. This allowed
the heated air to flow out under the lip in case some idiot put the >instruction manual on the top of the cabinet.
Another possibility, especially if there aren't going to be many of
these on sale and the installation will be done by the firm that makes >them, is to make a hole in the wall and stick some stainless-steel
boiler flues up the outside of the building. Even better, in an old >building. use a redundant fireplace and put the contol box in a
decorative housing on the mantlepiece.
We have in mind some commercial rackmount products, 1U to maybe 5U
dummy loads that people would buy and bolt into their 19" racks like
any other instrument. They would blow hot air out the back, like most
other gear.
On 12/4/24 22:55, Joe Gwinn wrote:
On Wed, 04 Dec 2024 13:29:03 -0800, john larkin <jl@glen--canyon.com>
wrote:
I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem
is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a
couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get
rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
Yes. A toaster element: Nichrome wire woven onto a mica card in a
perforated metal box.
Already packaged, one can get ballast resistors for high-power VFDs
used to power machine tools. The ballast resistor absorbs the energy
stored in a large chuck spinning fast, when it's time to come to a
stop quickly without over-voltage tripping the VFD.
.<https://www.automationdirect.com/adc/shopping/catalog/drives_-a-_soft_starters/ac_variable_frequency_drives_(vfd)/braking_units_-a-_resistors/br-n1-800w18p0>
Joe Gwinn
<https://www.reddit.com/r/CNC/comments/1es1d01/someone_didnt_believe_me_when_i_said_that_our/>
On Fri, 6 Dec 2024 17:56:05 +0100, Lasse Langwadt <llc@fonz.dk> wrote:
On 12/4/24 22:55, Joe Gwinn wrote:
On Wed, 04 Dec 2024 13:29:03 -0800, john larkin <jl@glen--canyon.com>
wrote:
I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem
is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a
couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get
rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC >>>> temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
Yes. A toaster element: Nichrome wire woven onto a mica card in a
perforated metal box.
Already packaged, one can get ballast resistors for high-power VFDs
used to power machine tools. The ballast resistor absorbs the energy
stored in a large chuck spinning fast, when it's time to come to a
stop quickly without over-voltage tripping the VFD.
.<https://www.automationdirect.com/adc/shopping/catalog/drives_-a-_soft_starters/ac_variable_frequency_drives_(vfd)/braking_units_-a-_resistors/br-n1-800w18p0>
Joe Gwinn
<https://www.reddit.com/r/CNC/comments/1es1d01/someone_didnt_believe_me_when_i_said_that_our/>
Yeah, small shops often do this kind of thing. Cheap, and works just
fine. Probably the original brake resistor had failed.
john larkin <JL@gct.com> wrote:
On Fri, 6 Dec 2024 08:29:33 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
John R Walliker <jrwalliker@gmail.com> wrote:
On 05/12/2024 22:03, Liz Tuddenham wrote:
john larkin <JL@gct.com> wrote:
On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <jl@glen--canyon.com> wrote:
I'm thinking about building a biggish rackmount dummy load box. It >> >> >>>> would simulate series resistance and inductance. Part of the problem >> >> >>>> is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a
couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get
rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
If you are using elements at near red heat, remember you need to
keep the radiant heat away from the outer walls of the cabinet.
Reflectors just throw the problem elsewhere and eventually will
tarnish, the best system is several spaced blackened steel baffle
plates with vertical air passages between them (visual black is not >> >> >>> always IR black).
Seems to me that black baffles will absorb IR and get hot, so devolve >> >> >> to air-cooled heat sinks.
Yes, all the energy is eventually going to finish up heating the air, >> >> > the only question is the pathway it takes. One way to avoid that would >> >> > be to construct a massive infra-red searchlight beaming the energy away >> >> > from the earth - or a broadcast transmitter beaming upwards.
To dump heat into the air, you either have to have something very
conductive with a large surface area or you need another way of
spreading the energy across a suface, such as heat radiation. A big
sheet of thin, blackened steel plate for heating by radiation is a lot >> >> > cheaper than a thick die-cast aluminium lump with fins for heating by >> >> > conduction.
The economics of mechanically-forced air cooling are better than
convection unless you are able to use a tall 'chimney', so that the
energy of the waste heat is used to generate the draught.
A full sized rack cabinet could be remarkably similar to a chimney
if it had baffles in the right places.
Yes, as long as the ceiling of the room isn't lined with polystyrene
tiles. It might not be very good for the air conditioning system in the
building where this is installed, regardless of which dissipation method
is used.
In the days of germainium transistors, one firm used to make cabinets
with a 'clerestory' roof, like an upturned tray suppoted on spacing
pillars above the ventilation holes in the roof proper. This allowed
the heated air to flow out under the lip in case some idiot put the
instruction manual on the top of the cabinet.
Another possibility, especially if there aren't going to be many of
these on sale and the installation will be done by the firm that makes
them, is to make a hole in the wall and stick some stainless-steel
boiler flues up the outside of the building. Even better, in an old
building. use a redundant fireplace and put the contol box in a
decorative housing on the mantlepiece.
We have in mind some commercial rackmount products, 1U to maybe 5U
dummy loads that people would buy and bolt into their 19" racks like
any other instrument. They would blow hot air out the back, like most
other gear.
You are going to need an awful lot of air if the exit temperature isn't
to be too high. Ordinary domestic fan heaters seem to be the best
starting point and some models would fit comfortably as a side-by-side
pair into a 5U 19" rack dissipating about 3kW each. Any more than about
1kW per Unit height is going to produce a dangerous temperature rise or
need a noisy high-speed blower to cool it.
On Fri, 6 Dec 2024 08:29:33 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
John R Walliker <jrwalliker@gmail.com> wrote:
On 05/12/2024 22:03, Liz Tuddenham wrote:
john larkin <JL@gct.com> wrote:
On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <jl@glen--canyon.com> wrote:
I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem >>> >>>> is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a >>> >>>> couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get >>> >>>> rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC >>> >>>> temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
If you are using elements at near red heat, remember you need to keep >>> >>> the radiant heat away from the outer walls of the cabinet. Reflectors >>> >>> just throw the problem elsewhere and eventually will tarnish, the best >>> >>> system is several spaced blackened steel baffle plates with vertical air
passages between them (visual black is not always IR black).
Seems to me that black baffles will absorb IR and get hot, so devolve >>> >> to air-cooled heat sinks.
Yes, all the energy is eventually going to finish up heating the air,
the only question is the pathway it takes. One way to avoid that would >>> > be to construct a massive infra-red searchlight beaming the energy away >>> > from the earth - or a broadcast transmitter beaming upwards.
To dump heat into the air, you either have to have something very
conductive with a large surface area or you need another way of
spreading the energy across a suface, such as heat radiation. A big
sheet of thin, blackened steel plate for heating by radiation is a lot >>> > cheaper than a thick die-cast aluminium lump with fins for heating by
conduction.
The economics of mechanically-forced air cooling are better than
convection unless you are able to use a tall 'chimney', so that the
energy of the waste heat is used to generate the draught.
A full sized rack cabinet could be remarkably similar to a chimney
if it had baffles in the right places.
Yes, as long as the ceiling of the room isn't lined with polystyrene
tiles. It might not be very good for the air conditioning system in the >>building where this is installed, regardless of which dissipation method
is used.
In the days of germainium transistors, one firm used to make cabinets
with a 'clerestory' roof, like an upturned tray suppoted on spacing
pillars above the ventilation holes in the roof proper. This allowed
the heated air to flow out under the lip in case some idiot put the >>instruction manual on the top of the cabinet.
Another possibility, especially if there aren't going to be many of
these on sale and the installation will be done by the firm that makes >>them, is to make a hole in the wall and stick some stainless-steel
boiler flues up the outside of the building. Even better, in an old >>building. use a redundant fireplace and put the contol box in a
decorative housing on the mantlepiece.
We have in mind some commercial rackmount products, 1U to maybe 5U
dummy loads that people would buy and bolt into their 19" racks like
any other instrument. They would blow hot air out the back, like most
other gear.
My users typically have cold forced air enter a rack from below and
expect it to exit near the top. I have one customer that controls the
air temp to milliKelvins, in what may be the world's biggest clean
room.
https://lasers.llnl.gov/multimedia/photo-gallery?tid%5B%5D=401&tid%5B%5D=402&
One rack that I know of is 2/3 full with kilowatts of Tek scopes and
ARBs. Things you need youngsters to help lift. I insisted that my
boxes be mounted BELOW the hot Tek stuff.
legg <legg@nospam.magma.ca> wrote:
On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <jl@glen--canyon.com> wrote:
I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem
is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a
couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get
rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
If you are using elements at near red heat, remember you need to keep
the radiant heat away from the outer walls of the cabinet. Reflectors
just throw the problem elsewhere and eventually will tarnish, the best
system is several spaced blackened steel baffle plates with vertical air
passages between them (visual black is not always IR black).
If you need a rapidly-controllable load, valves can dissipate energy at
a much higher temperature than transistors, so they might be worth
considering.
https://ve3ute.ca/2000a.html
Most of my valve designs err on the safe side. Putting electrolytic >capacitors where they can get hot is just plain stupid. I have seen
loads of shoddy radio/audio designs where the cathode resistor was
strapped along the side of the bypass capacitor or the main smoother was >stood up right next to the rectifier or the output valve.
On Thu, 5 Dec 2024 22:03:41 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
legg <legg@nospam.magma.ca> wrote:
On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <jl@glen--canyon.com> wrote:
I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem
is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a >>> >> couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get >>> >> rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC >>> >> temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
If you are using elements at near red heat, remember you need to keep
the radiant heat away from the outer walls of the cabinet. Reflectors
just throw the problem elsewhere and eventually will tarnish, the best
system is several spaced blackened steel baffle plates with vertical air >>> >passages between them (visual black is not always IR black).
If you need a rapidly-controllable load, valves can dissipate energy at >>> >a much higher temperature than transistors, so they might be worth
considering.
https://ve3ute.ca/2000a.html
Most of my valve designs err on the safe side. Putting electrolytic >>capacitors where they can get hot is just plain stupid. I have seen
loads of shoddy radio/audio designs where the cathode resistor was
strapped along the side of the bypass capacitor or the main smoother was >>stood up right next to the rectifier or the output valve.
By standard 'safe' design, tubes have a pretty limited life.
By 1956, the heater was no longer the weakest element in
the life equation for these parts - glass electrolysis was.
Electrolytic caps and their use has always been an issue.
Cuffing the tubes not only enforces distance to other
components, but reduces radiant effects in the viscinity.
Win, win.
RL
I have used some 2 watt resistors that showed about 600 degf by
iron/constantan but a red glow within could be seen by eye. Well above
stated limits of 2 watts. Can't remember the name they went by
but they were'nt wound types.
The aluminum housed resisters are handy. 50 watt types have
done much duty here.
Hul
I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem
is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a
couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get
rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem
is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a
couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get
rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
On 04-12-2024 22:29, john larkin wrote:
I'm thinking about building a biggish rackmount dummy load box. ItI have thought many times, but never got around to make an electronic
would simulate series resistance and inductance. Part of the problem
is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a
couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get
rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
load with many parallel circuits. At JLCPCB the mounting cost is low, so
no biggie
The idea is to spread the heat out, not relying on one element, but
many. Imagine a big PCB, like A3 size, spread out with 100 equal
circuits electronic loads. Frequency response would be high, power
dumping high also. Use a aluminum PCB like those used for LED lamps to
get even lower Rth
On Sat, 07 Dec 2024 11:49:14 -0500, legg <legg@nospam.magma.ca> wrote:
On Thu, 5 Dec 2024 22:03:41 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
legg <legg@nospam.magma.ca> wrote:
On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <jl@glen--canyon.com> wrote:
I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem >>>> >> is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a >>>> >> couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get >>>> >> rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC >>>> >> temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
If you are using elements at near red heat, remember you need to keep >>>> >the radiant heat away from the outer walls of the cabinet. Reflectors >>>> >just throw the problem elsewhere and eventually will tarnish, the best >>>> >system is several spaced blackened steel baffle plates with vertical air >>>> >passages between them (visual black is not always IR black).
If you need a rapidly-controllable load, valves can dissipate energy at >>>> >a much higher temperature than transistors, so they might be worth
considering.
https://ve3ute.ca/2000a.html
Most of my valve designs err on the safe side. Putting electrolytic >>>capacitors where they can get hot is just plain stupid. I have seen >>>loads of shoddy radio/audio designs where the cathode resistor was >>>strapped along the side of the bypass capacitor or the main smoother was >>>stood up right next to the rectifier or the output valve.
By standard 'safe' design, tubes have a pretty limited life.
By 1956, the heater was no longer the weakest element in
the life equation for these parts - glass electrolysis was.
Electrolytic caps and their use has always been an issue.
Cuffing the tubes not only enforces distance to other
components, but reduces radiant effects in the viscinity.
Win, win.
RL
Tubes were awful. Still are.
It's astounding that people built computers with tubes. Some had
hardware floating point!
On Sat, 07 Dec 2024 11:49:14 -0500, legg <legg@nospam.magma.ca> wrote:
On Thu, 5 Dec 2024 22:03:41 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
legg <legg@nospam.magma.ca> wrote:
On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <jl@glen--canyon.com> wrote:
I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem >>> >> is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a >>> >> couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get >>> >> rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC >>> >> temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
If you are using elements at near red heat, remember you need to keep >>> >the radiant heat away from the outer walls of the cabinet. Reflectors >>> >just throw the problem elsewhere and eventually will tarnish, the best >>> >system is several spaced blackened steel baffle plates with vertical air >>> >passages between them (visual black is not always IR black).
If you need a rapidly-controllable load, valves can dissipate energy at >>> >a much higher temperature than transistors, so they might be worth
considering.
https://ve3ute.ca/2000a.html
Most of my valve designs err on the safe side. Putting electrolytic >>capacitors where they can get hot is just plain stupid. I have seen >>loads of shoddy radio/audio designs where the cathode resistor was >>strapped along the side of the bypass capacitor or the main smoother was >>stood up right next to the rectifier or the output valve.
By standard 'safe' design, tubes have a pretty limited life.
By 1956, the heater was no longer the weakest element in
the life equation for these parts - glass electrolysis was.
Electrolytic caps and their use has always been an issue.
Cuffing the tubes not only enforces distance to other
components, but reduces radiant effects in the viscinity.
Win, win.
RL
Tubes were awful. Still are.
john larkin <JL@gct.com> wrote:
On Sat, 07 Dec 2024 11:49:14 -0500, legg <legg@nospam.magma.ca> wrote:
On Thu, 5 Dec 2024 22:03:41 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
legg <legg@nospam.magma.ca> wrote:
On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <jl@glen--canyon.com> wrote:
I'm thinking about building a biggish rackmount dummy load box. It >>>>>>> would simulate series resistance and inductance. Part of the problem >>>>>>> is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a >>>>>>> couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get >>>>>>> rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC >>>>>>> temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
If you are using elements at near red heat, remember you need to keep >>>>>> the radiant heat away from the outer walls of the cabinet. Reflectors >>>>>> just throw the problem elsewhere and eventually will tarnish, the best >>>>>> system is several spaced blackened steel baffle plates with vertical air >>>>>> passages between them (visual black is not always IR black).
If you need a rapidly-controllable load, valves can dissipate energy at >>>>>> a much higher temperature than transistors, so they might be worth >>>>>> considering.
https://ve3ute.ca/2000a.html
Most of my valve designs err on the safe side. Putting electrolytic
capacitors where they can get hot is just plain stupid. I have seen
loads of shoddy radio/audio designs where the cathode resistor was
strapped along the side of the bypass capacitor or the main smoother was >>>> stood up right next to the rectifier or the output valve.
By standard 'safe' design, tubes have a pretty limited life.
By 1956, the heater was no longer the weakest element in
the life equation for these parts - glass electrolysis was.
Electrolytic caps and their use has always been an issue.
Cuffing the tubes not only enforces distance to other
components, but reduces radiant effects in the viscinity.
Win, win.
RL
Tubes were awful. Still are.
The techniques for designing with them are quite different from
transistors and ICs, you have to think a different way; they aren't just
poor transistors, they have a different lifestyle altogether. They also
have some advantages over semiconductors:
1) Withstanding short term overloads without damage.
2) Dissipating energy in a smaller space at higher temperatures.
3) Easier to make with few exotic materials or processes.
4) EMP-proof and radiation-proof in the event of nuclear war.
Those properties aren't needed most of the time but when they are,
valves are a lot easier to design with than transistors if you are
conversant and comfortable with the technology. There are still very
few single transistors that can out-perform a humble EF91 from the
1940s.
Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:
john larkin <JL@gct.com> wrote:
On Sat, 07 Dec 2024 11:49:14 -0500, legg <legg@nospam.magma.ca> wrote:
On Thu, 5 Dec 2024 22:03:41 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
legg <legg@nospam.magma.ca> wrote:
On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid >>>>>> (Liz Tuddenham) wrote:
john larkin <jl@glen--canyon.com> wrote:
I'm thinking about building a biggish rackmount dummy load box. It >>>>>>>> would simulate series resistance and inductance. Part of the problem >>>>>>>> is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a >>>>>>>> couple of hundred watts, but I'd like to do a kilowatt or two. >>>>>>>>
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get >>>>>>>> rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC >>>>>>>> temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot >>>>>>>> nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
If you are using elements at near red heat, remember you need to keep >>>>>>> the radiant heat away from the outer walls of the cabinet. Reflectors >>>>>>> just throw the problem elsewhere and eventually will tarnish, the best >>>>>>> system is several spaced blackened steel baffle plates with vertical air
passages between them (visual black is not always IR black).
If you need a rapidly-controllable load, valves can dissipate energy at >>>>>>> a much higher temperature than transistors, so they might be worth >>>>>>> considering.
https://ve3ute.ca/2000a.html
Most of my valve designs err on the safe side. Putting electrolytic >>>>> capacitors where they can get hot is just plain stupid. I have seen >>>>> loads of shoddy radio/audio designs where the cathode resistor was
strapped along the side of the bypass capacitor or the main smoother was >>>>> stood up right next to the rectifier or the output valve.
By standard 'safe' design, tubes have a pretty limited life.
By 1956, the heater was no longer the weakest element in
the life equation for these parts - glass electrolysis was.
Electrolytic caps and their use has always been an issue.
Cuffing the tubes not only enforces distance to other
components, but reduces radiant effects in the viscinity.
Win, win.
RL
Tubes were awful. Still are.
The techniques for designing with them are quite different from
transistors and ICs, you have to think a different way; they aren't just
poor transistors, they have a different lifestyle altogether. They also
have some advantages over semiconductors:
1) Withstanding short term overloads without damage.
2) Dissipating energy in a smaller space at higher temperatures.
3) Easier to make with few exotic materials or processes.
4) EMP-proof and radiation-proof in the event of nuclear war.
Those properties aren't needed most of the time but when they are,
valves are a lot easier to design with than transistors if you are
conversant and comfortable with the technology. There are still very
few single transistors that can out-perform a humble EF91 from the
1940s.
<nearly dies laughing>
john larkin <JL@gct.com> wrote:
On Sat, 07 Dec 2024 11:49:14 -0500, legg <legg@nospam.magma.ca> wrote:
On Thu, 5 Dec 2024 22:03:41 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
legg <legg@nospam.magma.ca> wrote:
On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <jl@glen--canyon.com> wrote:
I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem >> >>> >> is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a >> >>> >> couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get >> >>> >> rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
If you are using elements at near red heat, remember you need to keep >> >>> >the radiant heat away from the outer walls of the cabinet. Reflectors >> >>> >just throw the problem elsewhere and eventually will tarnish, the best >> >>> >system is several spaced blackened steel baffle plates with vertical air
passages between them (visual black is not always IR black).
If you need a rapidly-controllable load, valves can dissipate energy at >> >>> >a much higher temperature than transistors, so they might be worth
considering.
https://ve3ute.ca/2000a.html
Most of my valve designs err on the safe side. Putting electrolytic
capacitors where they can get hot is just plain stupid. I have seen
loads of shoddy radio/audio designs where the cathode resistor was
strapped along the side of the bypass capacitor or the main smoother was >> >>stood up right next to the rectifier or the output valve.
By standard 'safe' design, tubes have a pretty limited life.
By 1956, the heater was no longer the weakest element in
the life equation for these parts - glass electrolysis was.
Electrolytic caps and their use has always been an issue.
Cuffing the tubes not only enforces distance to other
components, but reduces radiant effects in the viscinity.
Win, win.
RL
Tubes were awful. Still are.
The techniques for designing with them are quite different from
transistors and ICs, you have to think a different way; they aren't just
poor transistors, they have a different lifestyle altogether. They also
have some advantages over semiconductors:
1) Withstanding short term overloads without damage.
2) Dissipating energy in a smaller space at higher temperatures.
3) Easier to make with few exotic materials or processes.
4) EMP-proof and radiation-proof in the event of nuclear war.
Those properties aren't needed most of the time but when they are,
valves are a lot easier to design with than transistors if you are
conversant and comfortable with the technology. There are still very
few single transistors that can out-perform a humble EF91 from the
1940s.
Yup. EF91 is known as "Not the valve that won the war."
One could make an optocoupled tube half-bridge, or full-bridge, with
maybe a 30 KV supply. I guess you'd use batteries for filament power.
On a sunny day (Sun, 8 Dec 2024 13:33:39 +0000) it happened liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in <1r490yz.1xraied16vto76N%liz@poppyrecords.invalid.invalid>:
john larkin <JL@gct.com> wrote:
Tubes were awful. Still are.
The techniques for designing with them are quite different from
transistors and ICs, you have to think a different way; they aren't just >poor transistors, they have a different lifestyle altogether. They also >have some advantages over semiconductors:
1) Withstanding short term overloads without damage.
Thermal overloads depend on teh heatsink.
Jan Panteltje <alien@comet.invalid> wrote:
On a sunny day (Sun, 8 Dec 2024 13:33:39 +0000) it happened
liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
<1r490yz.1xraied16vto76N%liz@poppyrecords.invalid.invalid>:
john larkin <JL@gct.com> wrote:
[...]>RL
Tubes were awful. Still are.
The techniques for designing with them are quite different from
transistors and ICs, you have to think a different way; they aren't just
poor transistors, they have a different lifestyle altogether. They also
have some advantages over semiconductors:
1) Withstanding short term overloads without damage.
Thermal overloads depend on teh heatsink.
Only slow overloads. Fast ones depend on the thermal time constant of
the bit being heated by the overload. Some time later the energy
reaches the heat sink but but then the damage is done.
I've just accidentally mixed up the anode and grid pins of one of the
triodes in an ECC91. It drew about 100 mA for a few seconds with no
damage. That's equivalent to mixing up the Base and Collector
connections on a transistor and subjecting the Base-Emitter junction to
about 10 times the rated maximum Collector current. How many
transistors would survive that, even with the biggest heatsink
available?
On Sun, 8 Dec 2024 16:36:25 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Jan Panteltje <alien@comet.invalid> wrote:
On a sunny day (Sun, 8 Dec 2024 13:33:39 +0000) it happened
liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
<1r490yz.1xraied16vto76N%liz@poppyrecords.invalid.invalid>:
john larkin <JL@gct.com> wrote:
[...]>RL
Tubes were awful. Still are.
The techniques for designing with them are quite different from
transistors and ICs, you have to think a different way; they aren't just >> >poor transistors, they have a different lifestyle altogether. They also >> >have some advantages over semiconductors:
1) Withstanding short term overloads without damage.
Thermal overloads depend on teh heatsink.
Only slow overloads. Fast ones depend on the thermal time constant of
the bit being heated by the overload. Some time later the energy
reaches the heat sink but but then the damage is done.
I've just accidentally mixed up the anode and grid pins of one of the >triodes in an ECC91. It drew about 100 mA for a few seconds with no >damage. That's equivalent to mixing up the Base and Collector
connections on a transistor and subjecting the Base-Emitter junction to >about 10 times the rated maximum Collector current. How many
transistors would survive that, even with the biggest heatsink
available?
Mosfet data sheets usually have SOAR curves.
IXFH400N075T2 is rated for 1000 amps and 1000 watts (with astericks)
and 30 kilowatts for 25 uSec.
john larkin <JL@gct.com> wrote:
On Sun, 8 Dec 2024 16:36:25 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Jan Panteltje <alien@comet.invalid> wrote:
On a sunny day (Sun, 8 Dec 2024 13:33:39 +0000) it happened
liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
<1r490yz.1xraied16vto76N%liz@poppyrecords.invalid.invalid>:
john larkin <JL@gct.com> wrote:
[...]>RL
Tubes were awful. Still are.
The techniques for designing with them are quite different from
transistors and ICs, you have to think a different way; they aren't just >> >> >poor transistors, they have a different lifestyle altogether. They also >> >> >have some advantages over semiconductors:
1) Withstanding short term overloads without damage.
Thermal overloads depend on teh heatsink.
Only slow overloads. Fast ones depend on the thermal time constant of
the bit being heated by the overload. Some time later the energy
reaches the heat sink but but then the damage is done.
I've just accidentally mixed up the anode and grid pins of one of the
triodes in an ECC91. It drew about 100 mA for a few seconds with no
damage. That's equivalent to mixing up the Base and Collector
connections on a transistor and subjecting the Base-Emitter junction to
about 10 times the rated maximum Collector current. How many
transistors would survive that, even with the biggest heatsink
available?
Mosfet data sheets usually have SOAR curves.
IXFH400N075T2 is rated for 1000 amps and 1000 watts (with astericks)
and 30 kilowatts for 25 uSec.
Into the gate?
On 12/6/24 22:23, Joe Gwinn wrote:
On Fri, 6 Dec 2024 17:56:05 +0100, Lasse Langwadt <llc@fonz.dk> wrote:
On 12/4/24 22:55, Joe Gwinn wrote:
On Wed, 04 Dec 2024 13:29:03 -0800, john larkin <jl@glen--canyon.com>
wrote:
I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem >>>>> is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a >>>>> couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get >>>>> rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC >>>>> temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
Yes. A toaster element: Nichrome wire woven onto a mica card in a
perforated metal box.
Already packaged, one can get ballast resistors for high-power VFDs
used to power machine tools. The ballast resistor absorbs the energy
stored in a large chuck spinning fast, when it's time to come to a
stop quickly without over-voltage tripping the VFD.
.<https://www.automationdirect.com/adc/shopping/catalog/drives_-a-_soft_starters/ac_variable_frequency_drives_(vfd)/braking_units_-a-_resistors/br-n1-800w18p0>
Joe Gwinn
<https://www.reddit.com/r/CNC/comments/1es1d01/someone_didnt_believe_me_when_i_said_that_our/>
Yeah, small shops often do this kind of thing. Cheap, and works just
fine. Probably the original brake resistor had failed.
afaiu it came like that from the factory
On Sun, 8 Dec 2024 17:34:56 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sun, 8 Dec 2024 16:36:25 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Jan Panteltje <alien@comet.invalid> wrote:
On a sunny day (Sun, 8 Dec 2024 13:33:39 +0000) it happened
liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
<1r490yz.1xraied16vto76N%liz@poppyrecords.invalid.invalid>:
john larkin <JL@gct.com> wrote:
[...]>RL
Tubes were awful. Still are.
The techniques for designing with them are quite different from
transistors and ICs, you have to think a different way; they aren't
just poor transistors, they have a different lifestyle altogether.
They also have some advantages over semiconductors:
1) Withstanding short term overloads without damage.
Thermal overloads depend on teh heatsink.
Only slow overloads. Fast ones depend on the thermal time constant of
the bit being heated by the overload. Some time later the energy
reaches the heat sink but but then the damage is done.
I've just accidentally mixed up the anode and grid pins of one of the
triodes in an ECC91. It drew about 100 mA for a few seconds with no
damage. That's equivalent to mixing up the Base and Collector
connections on a transistor and subjecting the Base-Emitter junction to >> >about 10 times the rated maximum Collector current. How many
transistors would survive that, even with the biggest heatsink
available?
Mosfet data sheets usually have SOAR curves.
IXFH400N075T2 is rated for 1000 amps and 1000 watts (with astericks)
and 30 kilowatts for 25 uSec.
Into the gate?
Don't do that.
On Sun, 8 Dec 2024 14:15:54 -0000 (UTC), Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:
john larkin <JL@gct.com> wrote:
On Sat, 07 Dec 2024 11:49:14 -0500, legg <legg@nospam.magma.ca> wrote: >>>>
On Thu, 5 Dec 2024 22:03:41 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
legg <legg@nospam.magma.ca> wrote:
On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid >>>>>>> (Liz Tuddenham) wrote:
john larkin <jl@glen--canyon.com> wrote:
I'm thinking about building a biggish rackmount dummy load box. It >>>>>>>>> would simulate series resistance and inductance. Part of the problem >>>>>>>>> is that it will need to dump a lot of heat.If you are using elements at near red heat, remember you need to keep >>>>>>>> the radiant heat away from the outer walls of the cabinet. Reflectors >>>>>>>> just throw the problem elsewhere and eventually will tarnish, the best >>>>>>>> system is several spaced blackened steel baffle plates with vertical air
We are using copper CPU coolers on PC boards, which are great up to a >>>>>>>>> couple of hundred watts, but I'd like to do a kilowatt or two. >>>>>>>>>
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get >>>>>>>>> rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot >>>>>>>>> nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor. >>>>>>>>
passages between them (visual black is not always IR black).
If you need a rapidly-controllable load, valves can dissipate energy at
a much higher temperature than transistors, so they might be worth >>>>>>>> considering.
https://ve3ute.ca/2000a.html
Most of my valve designs err on the safe side. Putting electrolytic >>>>>> capacitors where they can get hot is just plain stupid. I have seen >>>>>> loads of shoddy radio/audio designs where the cathode resistor was >>>>>> strapped along the side of the bypass capacitor or the main smoother was >>>>>> stood up right next to the rectifier or the output valve.
By standard 'safe' design, tubes have a pretty limited life.
By 1956, the heater was no longer the weakest element in
the life equation for these parts - glass electrolysis was.
Electrolytic caps and their use has always been an issue.
Cuffing the tubes not only enforces distance to other
components, but reduces radiant effects in the viscinity.
Win, win.
RL
Tubes were awful. Still are.
The techniques for designing with them are quite different from
transistors and ICs, you have to think a different way; they aren't just >>> poor transistors, they have a different lifestyle altogether. They also >>> have some advantages over semiconductors:
1) Withstanding short term overloads without damage.
2) Dissipating energy in a smaller space at higher temperatures.
3) Easier to make with few exotic materials or processes.
4) EMP-proof and radiation-proof in the event of nuclear war.
Those properties aren't needed most of the time but when they are,
valves are a lot easier to design with than transistors if you are
conversant and comfortable with the technology. There are still very
few single transistors that can out-perform a humble EF91 from the
1940s.
<nearly dies laughing>
Yup. EF91 is known as "Not the valve that won the war."
Pentodes are *noisy*, at least 10 times more than some 3 cent jfet.
There are a couple of high-voltage tubes that were, until recently,
worth at least considering. But multi-KV fets are more sensible these
days.
I used to use the 1B3 HV rectifier diode as an amp, with the filament
voltage modulating the conductivity. The downsides were the bandwidth
and the X-ray hazard.
One could make an optocoupled tube half-bridge, or full-bridge, with
maybe a 30 KV supply. I guess you'd use batteries for filament power.
john larkin <JL@gct.com> wrote:
On Sun, 8 Dec 2024 17:34:56 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sun, 8 Dec 2024 16:36:25 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Jan Panteltje <alien@comet.invalid> wrote:
On a sunny day (Sun, 8 Dec 2024 13:33:39 +0000) it happened
liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
<1r490yz.1xraied16vto76N%liz@poppyrecords.invalid.invalid>:
john larkin <JL@gct.com> wrote:
[...]>RL
Tubes were awful. Still are.
The techniques for designing with them are quite different from
transistors and ICs, you have to think a different way; they aren't >> >> >> >just poor transistors, they have a different lifestyle altogether.
They also have some advantages over semiconductors:
1) Withstanding short term overloads without damage.
Thermal overloads depend on teh heatsink.
Only slow overloads. Fast ones depend on the thermal time constant of >> >> >the bit being heated by the overload. Some time later the energy
reaches the heat sink but but then the damage is done.
I've just accidentally mixed up the anode and grid pins of one of the
triodes in an ECC91. It drew about 100 mA for a few seconds with no
damage. That's equivalent to mixing up the Base and Collector
connections on a transistor and subjecting the Base-Emitter junction to >> >> >about 10 times the rated maximum Collector current. How many
transistors would survive that, even with the biggest heatsink
available?
Mosfet data sheets usually have SOAR curves.
IXFH400N075T2 is rated for 1000 amps and 1000 watts (with astericks)
and 30 kilowatts for 25 uSec.
Into the gate?
Don't do that.
...but that is the comparison with what I did by accident. I did it to
a device that was designed as an RF amplifier with a rated dissipation
of less than 3 watts and you were comparing it with a semiconductor that
was massively bigger - and now you say don't do that - and the device
needs extra protection components.
That was the point I was making: you can get away with mishaps in a
valve circuit that you can't get away with in a comparable transistor >circuit.
john larkin <jl@glen--canyon.com> wrote:
I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem
is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a
couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get
rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
Cooker hob ring?
I once used three industrial fan heaters as the starting resistor for a
large 3-phase motor with a big inertial load. They were wired in delta
but connected to the star point of the motor - an arrangement which gave
the required starting current and torque. After a predetermined time, a >normal 3-phase contactor shorted them out and closed the star point,
allowing the motor to run up to full speed. The system worked
flawlessly, up to 8 times a day, for several years.
Jan Panteltje <alien@comet.invalid> wrote:
On a sunny day (Sun, 8 Dec 2024 13:33:39 +0000) it happened
liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
<1r490yz.1xraied16vto76N%liz@poppyrecords.invalid.invalid>:
john larkin <JL@gct.com> wrote:
[...]>RL
Tubes were awful. Still are.
The techniques for designing with them are quite different from
transistors and ICs, you have to think a different way; they aren't just
poor transistors, they have a different lifestyle altogether. They also
have some advantages over semiconductors:
1) Withstanding short term overloads without damage.
Thermal overloads depend on teh heatsink.
Only slow overloads. Fast ones depend on the thermal time constant of
the bit being heated by the overload. Some time later the energy
reaches the heat sink but but then the damage is done.
I've just accidentally mixed up the anode and grid pins of one of the
triodes in an ECC91. It drew about 100 mA for a few seconds with no
damage. That's equivalent to mixing up the Base and Collector
connections on a transistor and subjecting the Base-Emitter junction to
about 10 times the rated maximum Collector current. How many
transistors would survive that, even with the biggest heatsink
available?
On Sun, 8 Dec 2024 17:34:56 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sun, 8 Dec 2024 16:36:25 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Jan Panteltje <alien@comet.invalid> wrote:
On a sunny day (Sun, 8 Dec 2024 13:33:39 +0000) it happened
liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
<1r490yz.1xraied16vto76N%liz@poppyrecords.invalid.invalid>:
john larkin <JL@gct.com> wrote:
[...]>RL
Tubes were awful. Still are.
The techniques for designing with them are quite different from
transistors and ICs, you have to think a different way; they aren't just
poor transistors, they have a different lifestyle altogether. They also
have some advantages over semiconductors:
1) Withstanding short term overloads without damage.
Thermal overloads depend on teh heatsink.
Only slow overloads. Fast ones depend on the thermal time constant of
the bit being heated by the overload. Some time later the energy
reaches the heat sink but but then the damage is done.
I've just accidentally mixed up the anode and grid pins of one of the
triodes in an ECC91. It drew about 100 mA for a few seconds with no
damage. That's equivalent to mixing up the Base and Collector
connections on a transistor and subjecting the Base-Emitter junction to >>> >about 10 times the rated maximum Collector current. How many
transistors would survive that, even with the biggest heatsink
available?
Mosfet data sheets usually have SOAR curves.
IXFH400N075T2 is rated for 1000 amps and 1000 watts (with astericks)
and 30 kilowatts for 25 uSec.
Into the gate?
Don't do that.
It's not hard to protect a mosfet from failure. The only way to
protect a tube from failure is to not use it.
A 1B3 makes a nice high-voltage capacitor, which is very reliable.
I have some beautiful tubes. 833 transmit jug. Some Blue Arcturus
things. A krytron. Some acorn and prox fuse tubes. A few gorgeous CRTs
and PMTs.
https://www.dropbox.com/scl/fo/m2ff4ty142v65omvmqf9k/ADvXu5nmmZ06w2hLulkZYL8?rlkey=z2tncdtgojshzogufp59xgxtw&dl=0
On Sun, 8 Dec 2024 21:08:42 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sun, 8 Dec 2024 17:34:56 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sun, 8 Dec 2024 16:36:25 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Jan Panteltje <alien@comet.invalid> wrote:
On a sunny day (Sun, 8 Dec 2024 13:33:39 +0000) it happened
liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
<1r490yz.1xraied16vto76N%liz@poppyrecords.invalid.invalid>:
john larkin <JL@gct.com> wrote:
[...]>RL
Tubes were awful. Still are.
The techniques for designing with them are quite different from
transistors and ICs, you have to think a different way; they aren't >> >> >> >just poor transistors, they have a different lifestyle altogether. >> >> >> >They also have some advantages over semiconductors:
1) Withstanding short term overloads without damage.
Thermal overloads depend on teh heatsink.
Only slow overloads. Fast ones depend on the thermal time constant of >> >> >the bit being heated by the overload. Some time later the energy
reaches the heat sink but but then the damage is done.
I've just accidentally mixed up the anode and grid pins of one of the >> >> >triodes in an ECC91. It drew about 100 mA for a few seconds with no >> >> >damage. That's equivalent to mixing up the Base and Collector
connections on a transistor and subjecting the Base-Emitter junction to
about 10 times the rated maximum Collector current. How many
transistors would survive that, even with the biggest heatsink
available?
Mosfet data sheets usually have SOAR curves.
IXFH400N075T2 is rated for 1000 amps and 1000 watts (with astericks)
and 30 kilowatts for 25 uSec.
Into the gate?
Don't do that.
...but that is the comparison with what I did by accident. I did it to
a device that was designed as an RF amplifier with a rated dissipation
of less than 3 watts and you were comparing it with a semiconductor that >was massively bigger - and now you say don't do that - and the device
needs extra protection components.
That was the point I was making: you can get away with mishaps in a
valve circuit that you can't get away with in a comparable transistor >circuit.
My first job interview, I told the guy that I preferred tubes to
transistors because it was harder to blow up tubes. He sniffed and
said "That won't do" and dismissed me.
On a sunny day (Sun, 8 Dec 2024 16:36:25 +0000) it happened liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in <1r499nc.1l79pftrqcriyN%liz@poppyrecords.invalid.invalid>:
Jan Panteltje <alien@comet.invalid> wrote:
On a sunny day (Sun, 8 Dec 2024 13:33:39 +0000) it happened
liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
<1r490yz.1xraied16vto76N%liz@poppyrecords.invalid.invalid>:
john larkin <JL@gct.com> wrote:
[...]>RL
Tubes were awful. Still are.
The techniques for designing with them are quite different from
transistors and ICs, you have to think a different way; they aren't just >> >poor transistors, they have a different lifestyle altogether. They also >> >have some advantages over semiconductors:
1) Withstanding short term overloads without damage.
Thermal overloads depend on teh heatsink.
Only slow overloads. Fast ones depend on the thermal time constant of
the bit being heated by the overload. Some time later the energy
reaches the heat sink but but then the damage is done.
I've just accidentally mixed up the anode and grid pins of one of the >triodes in an ECC91. It drew about 100 mA for a few seconds with no >damage. That's equivalent to mixing up the Base and Collector
connections on a transistor and subjecting the Base-Emitter junction to >about 10 times the rated maximum Collector current. How many
transistors would survive that, even with the biggest heatsink
available?
The 100 mA is a current limit due to the limited electron emission
possible from that cathode at those settings. You can get flash-over with anode voltage at the grid of toobs.
I understand you love toobs, sure toobs were nice
9) touch screen????
10) X-Ray emission from the monitor HV stabilizer tubes..
I modified it to drive that real old magnetic deflection TV set with transistors HV tronsformer, the works. Was an interesting learning
curve... Never longed back to toobs after that.
Jan Panteltje <alien@comet.invalid> wrote:
On a sunny day (Sun, 8 Dec 2024 16:36:25 +0000) it happened
liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
<1r499nc.1l79pftrqcriyN%liz@poppyrecords.invalid.invalid>:
Jan Panteltje <alien@comet.invalid> wrote:
On a sunny day (Sun, 8 Dec 2024 13:33:39 +0000) it happened
liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
<1r490yz.1xraied16vto76N%liz@poppyrecords.invalid.invalid>:
john larkin <JL@gct.com> wrote:
[...]>RL
Tubes were awful. Still are.
The techniques for designing with them are quite different from
transistors and ICs, you have to think a different way; they aren't just >> >> >poor transistors, they have a different lifestyle altogether. They also >> >> >have some advantages over semiconductors:
1) Withstanding short term overloads without damage.
Thermal overloads depend on teh heatsink.
Only slow overloads. Fast ones depend on the thermal time constant of
the bit being heated by the overload. Some time later the energy
reaches the heat sink but but then the damage is done.
I've just accidentally mixed up the anode and grid pins of one of the
triodes in an ECC91. It drew about 100 mA for a few seconds with no
damage. That's equivalent to mixing up the Base and Collector
connections on a transistor and subjecting the Base-Emitter junction to
about 10 times the rated maximum Collector current. How many
transistors would survive that, even with the biggest heatsink
available?
The 100 mA is a current limit due to the limited electron emission
possible from that cathode at those settings. You can get flash-over with
anode voltage at the grid of toobs.
There was a 1k current-limiting resistor in the HT supply (it changed >colour). At least I had time to get to the 'off' switch before the
valve could be seriously damaged. Luckily I was testing with reduced HT >(about 100v) so the current would have been limited to about 100mA by
the resistor, even if the maximum emission had been greater
I understand you love toobs, sure toobs were nice
I enjoy designing with them, rather than just copying well-worn
circuits. There are still niches to be explored.
A few years ago I set myself the task of designing a low-noise audio
preamp using a grounded-grid first stage - the result was far better
than I had expected because it had repercussions on the second stage and
the mixing stage which greatly improved the overload performance and the
S/N ratio of the whole amplifier. If I had invented that in the 1950s,
I would be a lot richer now.
I sent copies of the 'before' and 'after' circuits to a friend who is a
great believer in the mystical properties of valves, but is otherwise
quite sensible. It took him two days to get his mind around how the
circuit actually worked.
[...]
9) touch screen????
I have never needed a touch screen. The only time I have used them is
at supermarkets and that was for their convenience, not mine.
10) X-Ray emission from the monitor HV stabilizer tubes..
Grossly over-hyped.
[...]
I modified it to drive that real old magnetic deflection TV set with
transistors HV tronsformer, the works. Was an interesting learning
curve... Never longed back to toobs after that.
My first experience with transistors was building a simple automatic
parking light for a car from a circuit in a magazine. It used a >photoconductive cell to switch a chain of ever-larger transistors and
supply a 12v bulb. The idiot who 'designed' it had added negative
feedback instead of positive feedback, so the bulb never went right out
and never came full on. The heatsink got hot and it ran down the car
battery in daylight.
It took a long time after that before I felt happy with transistors.
john larkin <JL@gct.com> wrote:
On Sun, 8 Dec 2024 21:08:42 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sun, 8 Dec 2024 17:34:56 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sun, 8 Dec 2024 16:36:25 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Jan Panteltje <alien@comet.invalid> wrote:
On a sunny day (Sun, 8 Dec 2024 13:33:39 +0000) it happened
liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
<1r490yz.1xraied16vto76N%liz@poppyrecords.invalid.invalid>:
john larkin <JL@gct.com> wrote:
[...]>RL
Tubes were awful. Still are.
The techniques for designing with them are quite different from
transistors and ICs, you have to think a different way; they aren't
just poor transistors, they have a different lifestyle altogether. >> >> >> >> >They also have some advantages over semiconductors:
1) Withstanding short term overloads without damage.
Thermal overloads depend on teh heatsink.
Only slow overloads. Fast ones depend on the thermal time constant of
the bit being heated by the overload. Some time later the energy
reaches the heat sink but but then the damage is done.
I've just accidentally mixed up the anode and grid pins of one of the >> >> >> >triodes in an ECC91. It drew about 100 mA for a few seconds with no >> >> >> >damage. That's equivalent to mixing up the Base and Collector
connections on a transistor and subjecting the Base-Emitter junction to
about 10 times the rated maximum Collector current. How many
transistors would survive that, even with the biggest heatsink
available?
Mosfet data sheets usually have SOAR curves.
IXFH400N075T2 is rated for 1000 amps and 1000 watts (with astericks) >> >> >> and 30 kilowatts for 25 uSec.
Into the gate?
Don't do that.
...but that is the comparison with what I did by accident. I did it to
a device that was designed as an RF amplifier with a rated dissipation
of less than 3 watts and you were comparing it with a semiconductor that
was massively bigger - and now you say don't do that - and the device
needs extra protection components.
That was the point I was making: you can get away with mishaps in a
valve circuit that you can't get away with in a comparable transistor
circuit.
My first job interview, I told the guy that I preferred tubes to
transistors because it was harder to blow up tubes. He sniffed and
said "That won't do" and dismissed me.
I was asked the same question at my first job interview. I just said I >understood valves better, which was true at the time. The Chief
Engineer, who was interviewing me, then produced the circuit diagram of
one of the firm's valve communications receivers and asked me to go
through it and tell him what each part did.
I took one look at it and said "Yuck! It's chassis-live". My
interviewer let me continue and then gave me the job. It turned out
later that he hated having to make the set that way but for commercial >reasons it had to work on 110v D.C. and therefore had to have the
chassis connected to one pole of the mains. (The chassis was well
insulated from the casing and all the outside fittings and connections.)
Throughout the entire job with that firm, I never had to design with
valves - but I did ten years later when I had to make some high voltage >research equipment.
On Wed, 4 Dec 2024 22:32:33 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <jl@glen--canyon.com> wrote:
I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem
is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a
couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get
rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
Cooker hob ring?
What's that in American ??!!
On Mon, 9 Dec 2024 09:33:35 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sun, 8 Dec 2024 21:08:42 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sun, 8 Dec 2024 17:34:56 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sun, 8 Dec 2024 16:36:25 +0000, liz@poppyrecords.invalid.invalid >>>>>>> (Liz Tuddenham) wrote:
Jan Panteltje <alien@comet.invalid> wrote:
On a sunny day (Sun, 8 Dec 2024 13:33:39 +0000) it happened
liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
<1r490yz.1xraied16vto76N%liz@poppyrecords.invalid.invalid>:
john larkin <JL@gct.com> wrote:
[...]>RL
Tubes were awful. Still are.
The techniques for designing with them are quite different from >>>>>>>>>> transistors and ICs, you have to think a different way; they aren't >>>>>>>>>> just poor transistors, they have a different lifestyle altogether. >>>>>>>>>> They also have some advantages over semiconductors:
1) Withstanding short term overloads without damage.
Thermal overloads depend on teh heatsink.
Only slow overloads. Fast ones depend on the thermal time constant of >>>>>>>> the bit being heated by the overload. Some time later the energy >>>>>>>> reaches the heat sink but but then the damage is done.
I've just accidentally mixed up the anode and grid pins of one of the >>>>>>>> triodes in an ECC91. It drew about 100 mA for a few seconds with no >>>>>>>> damage. That's equivalent to mixing up the Base and Collector >>>>>>>> connections on a transistor and subjecting the Base-Emitter junction to
about 10 times the rated maximum Collector current. How many
transistors would survive that, even with the biggest heatsink >>>>>>>> available?
Mosfet data sheets usually have SOAR curves.
IXFH400N075T2 is rated for 1000 amps and 1000 watts (with astericks) >>>>>>> and 30 kilowatts for 25 uSec.
Into the gate?
Don't do that.
...but that is the comparison with what I did by accident. I did it to >>>> a device that was designed as an RF amplifier with a rated dissipation >>>> of less than 3 watts and you were comparing it with a semiconductor that >>>> was massively bigger - and now you say don't do that - and the device
needs extra protection components.
That was the point I was making: you can get away with mishaps in a
valve circuit that you can't get away with in a comparable transistor
circuit.
My first job interview, I told the guy that I preferred tubes to
transistors because it was harder to blow up tubes. He sniffed and
said "That won't do" and dismissed me.
I was asked the same question at my first job interview. I just said I
understood valves better, which was true at the time. The Chief
Engineer, who was interviewing me, then produced the circuit diagram of
one of the firm's valve communications receivers and asked me to go
through it and tell him what each part did.
I took one look at it and said "Yuck! It's chassis-live". My
interviewer let me continue and then gave me the job. It turned out
later that he hated having to make the set that way but for commercial
reasons it had to work on 110v D.C. and therefore had to have the
chassis connected to one pole of the mains. (The chassis was well
insulated from the casing and all the outside fittings and connections.)
Throughout the entire job with that firm, I never had to design with
valves - but I did ten years later when I had to make some high voltage
research equipment.
My Hallicrafters S38 was a metal box with a hot chassis inside and all
the grommets had long ago failed. so I had to plug it in the right
way, with unpolarized outlets. I attached a neon lamp to the top; if I touched it and it lit up, I'd switch the plug.
People used to soak in their bathtub with a radio on the table. If it
fell into the water, they would die.
Life was cheap, back then.
I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem
is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a
couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get
rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
On 12/8/2024 9:04 PM, john larkin wrote:hvnetw=g&hvrand=12073860510026011302&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9004204&hvtargid=pla-2281435183338&psc=1
On Wed, 4 Dec 2024 22:32:33 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <jl@glen--canyon.com> wrote:
I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem
is that it will need to dump a lot of heat.
We are using copper CPU coolers on PC boards, which are great up to a
couple of hundred watts, but I'd like to do a kilowatt or two.
https://highlandtechnology.com/Product/P945
It would take a heap of expensive extruded heat sinks and fans to get
rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC >>>> temp rise.
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
I'd prefer to not use water.
I wonder if there is some sort of runs-red-hot power resistor.
Cooker hob ring?
What's that in American ??!!
:-)
https://www.amazon.com/LXun-Electric-Included-Replacement-Whirlpool/dp/B08BLJYTD4/ref=asc_df_B08BLJYTD4?mcid=6a1fcb0f8a9b374fb92357f05f23bb39&hvocijid=12073860510026011302-B08BLJYTD4-&hvexpln=73&tag=hyprod-20&linkCode=df0&hvadid=692875362841&hvpos=&
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