• Cooling a TO-220 7812 regulator

    From Pimpom@21:1/5 to All on Sun Sep 15 16:58:01 2024
    I'm going to use a standard 7812 TO-220 regulator on a single-sided 1 oz
    board with the dissipation varying as below:

    - Idle at 120-150mW
    - 0.5W for 1-5 minutes at irregular intervals
    - Up to 4W for 1 second at the start of each 0.5W phase

    The interval between the 1-5-minute periods is variable and may be 1 to
    10 minutes.

    The ground pin is soldered to ~2 sq.in. of copper on the PCB.

    Options:
    1) As described. No extra heatsinking.
    2) Mount it on a small Al heatsink.
    3) Place the regulator horizontally on the underside and bolt it to the
    copper.

    Tamb = ~35ºC max

    Do you think option 1) is enough? Or should I go for 2) or 3)?

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Martin Brown@21:1/5 to Pimpom on Sun Sep 15 13:41:09 2024
    On 15/09/2024 12:28, Pimpom wrote:
    I'm going to use a standard 7812 TO-220 regulator on a single-sided 1 oz board with the dissipation varying as below:

    - Idle at 120-150mW
    - 0.5W for 1-5 minutes at irregular intervals
    - Up to 4W for 1 second at the start of each 0.5W phase

    The interval between the 1-5-minute periods is variable and may be 1 to
    10 minutes.

    The ground pin is soldered to ~2 sq.in. of copper on the PCB.

    Options:
    1) As described. No extra heatsinking.
    2) Mount it on a small Al heatsink.
    3) Place the regulator horizontally on the underside and bolt it to the copper.

    Tamb = ~35ºC max

    Do you think option 1) is enough? Or should I go for 2) or 3)?

    I suspect that under those load conditions you will get away with it #1.
    I'm pretty sure the package is well able to handle that dissipation and
    if it can't it will fold back to thermally protect itself (in which case
    you will have to add a bit more heatsinking).

    I once built a 78xx based PSU that was in a bright bare metal aluminium extruded box expecting it to be more than adequate heatsinking. It
    wasn't! The bright metal was a terrible radiator and it got hot enough
    to go into thermal foldback. A bit of matt black paint fixed that.

    --
    Martin Brown

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jan Panteltje@21:1/5 to Pimpom@invalid.invalid on Sun Sep 15 14:56:59 2024
    On a sunny day (Sun, 15 Sep 2024 16:58:01 +0530) it happened Pimpom <Pimpom@invalid.invalid> wrote in <5xzFO.64422$lZG8.30677@fx09.ams1>:

    I'm going to use a standard 7812 TO-220 regulator on a single-sided 1 oz >board with the dissipation varying as below:

    - Idle at 120-150mW
    - 0.5W for 1-5 minutes at irregular intervals
    - Up to 4W for 1 second at the start of each 0.5W phase

    The interval between the 1-5-minute periods is variable and may be 1 to
    10 minutes.

    The ground pin is soldered to ~2 sq.in. of copper on the PCB.

    Options:
    1) As described. No extra heatsinking.
    2) Mount it on a small Al heatsink.
    3) Place the regulator horizontally on the underside and bolt it to the >copper.

    Tamb = ~35ºC max

    Do you think option 1) is enough? Or should I go for 2) or 3)?

    Rth to ambient is about 50 IIRC
    so 4 W long enough makes a 200 degrees rise..
    .5W makes a 32 degrees rise.
    But the thing will thermal limit
    That limit may affect whatever it is you power from it.
    I always used cheap small heatsinks with the thing standing up,
    no need to warm the PCB whith maybe sensitive stuff on it
    If you have an alu housing an need more power screw it against that, pehaps with a Mica insulator
    https://panteltje.nl/pub/8052AH_BASIC_computer/8052AH_BASIC_computer_inside_img_1727.jpg

    If all else fails, biiger heatsink, this is the biggest one I have :
    https://panteltje.nl/pub/big_heatsink_IMG_6292.JPG
    :-)

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Pimpom@21:1/5 to Martin Brown on Sun Sep 15 21:18:51 2024
    On 15-09-2024 06:11 pm, Martin Brown wrote:
    On 15/09/2024 12:28, Pimpom wrote:
    I'm going to use a standard 7812 TO-220 regulator on a single-sided 1
    oz board with the dissipation varying as below:

    - Idle at 120-150mW
    - 0.5W for 1-5 minutes at irregular intervals
    - Up to 4W for 1 second at the start of each 0.5W phase

    The interval between the 1-5-minute periods is variable and may be 1
    to 10 minutes.

    The ground pin is soldered to ~2 sq.in. of copper on the PCB.

    Options:
    1) As described. No extra heatsinking.
    2) Mount it on a small Al heatsink.
    3) Place the regulator horizontally on the underside and bolt it to
    the copper.

    Tamb = ~35ºC max

    Do you think option 1) is enough? Or should I go for 2) or 3)?

    I suspect that under those load conditions you will get away with it #1.
    I'm pretty sure the package is well able to handle that dissipation and
    if it can't it will fold back to thermally protect itself (in which case
    you will have to add a bit more heatsinking).

    I once built a 78xx based PSU that was in a bright bare metal aluminium extruded box expecting it to be more than adequate heatsinking. It
    wasn't! The bright metal was a terrible radiator and it got hot enough
    to go into thermal foldback. A bit of matt black paint fixed that.

    Thanks. I'm inclined to think that way too. Calculating temerature rise
    and heatsink requirement for steady-state dissipation is simple enough
    and it's easy to make a good guesstimate from experience. But transient
    cases like this are different.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to All on Sun Sep 15 09:16:20 2024
    On Sun, 15 Sep 2024 16:58:01 +0530, Pimpom <Pimpom@invalid.invalid>
    wrote:

    I'm going to use a standard 7812 TO-220 regulator on a single-sided 1 oz >board with the dissipation varying as below:

    - Idle at 120-150mW
    - 0.5W for 1-5 minutes at irregular intervals
    - Up to 4W for 1 second at the start of each 0.5W phase

    The interval between the 1-5-minute periods is variable and may be 1 to
    10 minutes.

    The ground pin is soldered to ~2 sq.in. of copper on the PCB.

    Options:
    1) As described. No extra heatsinking.
    2) Mount it on a small Al heatsink.
    3) Place the regulator horizontally on the underside and bolt it to the >copper.

    Tamb = ~35C max

    Do you think option 1) is enough? Or should I go for 2) or 3)?

    Option 1 sounds fine to me. It will barely get warm.

    You don't need it, but internal plane layers help spread out heat too.

    https://www.dropbox.com/scl/fo/l0pfn2qtj9pylri0kxnbs/ADjThVe5WV989K8DgotdKVI?rlkey=z4gtiaxmnybem099s6l9yz20m&dl=0

    https://www.dropbox.com/scl/fo/dcua00tr8fgxtudnqzhzr/APMIydE2mZFz5e2aFRd-2TY?rlkey=2y16ic2watsnfnthzcf7zbt0i&dl=0

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Pimpom@21:1/5 to john larkin on Sun Sep 15 23:03:09 2024
    On 15-09-2024 09:46 pm, john larkin wrote:
    On Sun, 15 Sep 2024 16:58:01 +0530, Pimpom <Pimpom@invalid.invalid>
    wrote:

    I'm going to use a standard 7812 TO-220 regulator on a single-sided 1 oz
    board with the dissipation varying as below:

    - Idle at 120-150mW
    - 0.5W for 1-5 minutes at irregular intervals
    - Up to 4W for 1 second at the start of each 0.5W phase

    The interval between the 1-5-minute periods is variable and may be 1 to
    10 minutes.

    The ground pin is soldered to ~2 sq.in. of copper on the PCB.

    Options:
    1) As described. No extra heatsinking.
    2) Mount it on a small Al heatsink.
    3) Place the regulator horizontally on the underside and bolt it to the
    copper.

    Tamb = ~35ºC max

    Do you think option 1) is enough? Or should I go for 2) or 3)?

    Option 1 sounds fine to me. It will barely get warm.

    You don't need it, but internal plane layers help spread out heat too.

    https://www.dropbox.com/scl/fo/l0pfn2qtj9pylri0kxnbs/ADjThVe5WV989K8DgotdKVI?rlkey=z4gtiaxmnybem099s6l9yz20m&dl=0

    https://www.dropbox.com/scl/fo/dcua00tr8fgxtudnqzhzr/APMIydE2mZFz5e2aFRd-2TY?rlkey=2y16ic2watsnfnthzcf7zbt0i&dl=0

    Thanks for the input. Calculating heatsink requirement for continuous dissipation is one thing. Short bursts are another.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Pimpom@21:1/5 to Jan Panteltje on Sun Sep 15 23:00:12 2024
    On 15-09-2024 08:26 pm, Jan Panteltje wrote:
    On a sunny day (Sun, 15 Sep 2024 16:58:01 +0530) it happened Pimpom <Pimpom@invalid.invalid> wrote in <5xzFO.64422$lZG8.30677@fx09.ams1>:

    I'm going to use a standard 7812 TO-220 regulator on a single-sided 1 oz
    board with the dissipation varying as below:

    - Idle at 120-150mW
    - 0.5W for 1-5 minutes at irregular intervals
    - Up to 4W for 1 second at the start of each 0.5W phase

    The interval between the 1-5-minute periods is variable and may be 1 to
    10 minutes.

    The ground pin is soldered to ~2 sq.in. of copper on the PCB.

    Options:
    1) As described. No extra heatsinking.
    2) Mount it on a small Al heatsink.
    3) Place the regulator horizontally on the underside and bolt it to the
    copper.

    Tamb = ~35ºC max

    Do you think option 1) is enough? Or should I go for 2) or 3)?

    Rth to ambient is about 50 IIRC
    so 4 W long enough makes a 200 degrees rise..
    .5W makes a 32 degrees rise.
    But the thing will thermal limit
    That limit may affect whatever it is you power from it.

    The 'up to 4W' burst is timed to 1 sec. I think there's enough thermal
    mass to keep Tj from reaching a critical temp in that time. But then
    that's where I'm asking for the group's collective wisdom.

    I always used cheap small heatsinks with the thing standing up,

    I do that when there's a significant amount of continuous dissipation.

    no need to warm the PCB whith maybe sensitive stuff on it

    No sensitive parts anywhere close by.

    If you have an alu housing an need more power screw it against that, pehaps with a Mica insulator

    I've done that many times. In this particular case though, the PCB has
    to be more than an inch away from the wall.

    https://panteltje.nl/pub/8052AH_BASIC_computer/8052AH_BASIC_computer_inside_img_1727.jpg

    If all else fails, biiger heatsink, this is the biggest one I have :
    https://panteltje.nl/pub/big_heatsink_IMG_6292.JPG
    :-)

    Oh yeah, I've used some huge heatsinks too, when I was into audio and
    output transistors could easily dissipate several tens of watts each -
    and cooling fans were not easily available here. And then there was the
    time I made a limited production using 40A SSRs some 30 years ago.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to All on Sun Sep 15 11:55:40 2024
    On Sun, 15 Sep 2024 23:03:09 +0530, Pimpom <Pimpom@invalid.invalid>
    wrote:

    On 15-09-2024 09:46 pm, john larkin wrote:
    On Sun, 15 Sep 2024 16:58:01 +0530, Pimpom <Pimpom@invalid.invalid>
    wrote:

    I'm going to use a standard 7812 TO-220 regulator on a single-sided 1 oz >>> board with the dissipation varying as below:

    - Idle at 120-150mW
    - 0.5W for 1-5 minutes at irregular intervals
    - Up to 4W for 1 second at the start of each 0.5W phase

    The interval between the 1-5-minute periods is variable and may be 1 to
    10 minutes.

    The ground pin is soldered to ~2 sq.in. of copper on the PCB.

    Options:
    1) As described. No extra heatsinking.
    2) Mount it on a small Al heatsink.
    3) Place the regulator horizontally on the underside and bolt it to the
    copper.

    Tamb = ~35C max

    Do you think option 1) is enough? Or should I go for 2) or 3)?

    Option 1 sounds fine to me. It will barely get warm.

    You don't need it, but internal plane layers help spread out heat too.

    https://www.dropbox.com/scl/fo/l0pfn2qtj9pylri0kxnbs/ADjThVe5WV989K8DgotdKVI?rlkey=z4gtiaxmnybem099s6l9yz20m&dl=0

    https://www.dropbox.com/scl/fo/dcua00tr8fgxtudnqzhzr/APMIydE2mZFz5e2aFRd-2TY?rlkey=2y16ic2watsnfnthzcf7zbt0i&dl=0

    Thanks for the input. Calculating heatsink requirement for continuous >dissipation is one thing. Short bursts are another.

    You can estimate the mass and specific heat of a fet and do the math.
    It's even easier to test one. You could do that quickly.

    Given a TO-220 gadget, it would be nice to know the temp rise per
    joule dumped into it. Maybe I'll measure that.

    First google hit:

    https://www.avrfreaks.net/s/topic/a5C3l000000UNfNEAW/t104767

    "A TO-220 package has a thermal capacitance of 0.54(J/C) and thermal
    resistance of about 62(C/W) without a heatsink."

    Based on that, 4 watts for 1 second works out to about 8C rise. The
    PCB will help a little.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Pimpom@21:1/5 to john larkin on Mon Sep 16 01:11:45 2024
    On 16-09-2024 12:25 am, john larkin wrote:
    On Sun, 15 Sep 2024 23:03:09 +0530, Pimpom <Pimpom@invalid.invalid>
    wrote:


    Thanks for the input. Calculating heatsink requirement for continuous
    dissipation is one thing. Short bursts are another.

    You can estimate the mass and specific heat of a fet and do the math.
    It's even easier to test one. You could do that quickly.

    Given a TO-220 gadget, it would be nice to know the temp rise per
    joule dumped into it. Maybe I'll measure that.

    First google hit:

    https://www.avrfreaks.net/s/topic/a5C3l000000UNfNEAW/t104767

    "A TO-220 package has a thermal capacitance of 0.54(J/C) and thermal resistance of about 62(C/W) without a heatsink."

    Based on that, 4 watts for 1 second works out to about 8C rise. The
    PCB will help a little.

    That's good to know. Even if those data are a bit off, it still leaves
    plenty of headroom for a safe operation including hotspots on the chip.

    BTW I think it was you who mentioned Saturn PCB Toolkit in a thread
    several years ago. I've been using it since then. It's a useful tool.

    There was a time when they seemed to have blocked downloads from outside
    the US. They didn't actually say so and it took me some time to figure
    it out. I managed to get around that with a VPN. I'm using v8.39 now.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to All on Sun Sep 15 12:56:23 2024
    On Mon, 16 Sep 2024 01:11:45 +0530, Pimpom <Pimpom@invalid.invalid>
    wrote:

    On 16-09-2024 12:25 am, john larkin wrote:
    On Sun, 15 Sep 2024 23:03:09 +0530, Pimpom <Pimpom@invalid.invalid>
    wrote:


    Thanks for the input. Calculating heatsink requirement for continuous
    dissipation is one thing. Short bursts are another.

    You can estimate the mass and specific heat of a fet and do the math.
    It's even easier to test one. You could do that quickly.

    Given a TO-220 gadget, it would be nice to know the temp rise per
    joule dumped into it. Maybe I'll measure that.

    First google hit:

    https://www.avrfreaks.net/s/topic/a5C3l000000UNfNEAW/t104767

    "A TO-220 package has a thermal capacitance of 0.54(J/C) and thermal
    resistance of about 62(C/W) without a heatsink."

    Based on that, 4 watts for 1 second works out to about 8C rise. The
    PCB will help a little.

    That's good to know. Even if those data are a bit off, it still leaves
    plenty of headroom for a safe operation including hotspots on the chip.

    BTW I think it was you who mentioned Saturn PCB Toolkit in a thread
    several years ago. I've been using it since then. It's a useful tool.

    There was a time when they seemed to have blocked downloads from outside
    the US. They didn't actually say so and it took me some time to figure
    it out. I managed to get around that with a VPN. I'm using v8.39 now.

    Saturn is great, but the current version defaults to a hideous color
    scheme, which fortunately can be fixed.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Bill Sloman@21:1/5 to Pimpom on Tue Sep 17 02:32:17 2024
    On 16/09/2024 1:48 am, Pimpom wrote:
    On 15-09-2024 06:11 pm, Martin Brown wrote:
    On 15/09/2024 12:28, Pimpom wrote:
    I'm going to use a standard 7812 TO-220 regulator on a single-sided 1
    oz board with the dissipation varying as below:

    - Idle at 120-150mW
    - 0.5W for 1-5 minutes at irregular intervals
    - Up to 4W for 1 second at the start of each 0.5W phase

    The interval between the 1-5-minute periods is variable and may be 1
    to 10 minutes.

    The ground pin is soldered to ~2 sq.in. of copper on the PCB.

    Options:
    1) As described. No extra heatsinking.
    2) Mount it on a small Al heatsink.
    3) Place the regulator horizontally on the underside and bolt it to
    the copper.

    Tamb = ~35ºC max

    Do you think option 1) is enough? Or should I go for 2) or 3)?

    I suspect that under those load conditions you will get away with it
    #1. I'm pretty sure the package is well able to handle that
    dissipation and if it can't it will fold back to thermally protect
    itself (in which case you will have to add a bit more heatsinking).

    I once built a 78xx based PSU that was in a bright bare metal
    aluminium extruded box expecting it to be more than adequate
    heatsinking. It wasn't! The bright metal was a terrible radiator and
    it got hot enough to go into thermal foldback. A bit of matt black
    paint fixed that.

    Thanks. I'm inclined to think that way too. Calculating temerature rise
    and heatsink requirement for steady-state dissipation is simple enough
    and it's easy to make a good guesstimate from experience. But transient
    cases like this are different.

    It's not that difficult to weigh a chunk of material and calculate it's
    heat capacity. We did it back in 1993.

    Sloman A.W., Buggs P., Molloy J., and Stewart D. “A
    microcontroller-based driver to stabilise the temperature of an optical
    stage to 1mK in the range 4C to 38C, using a Peltier heat pump and a
    thermistor sensor” Measurement Science and Technology, 7 1653-64 (1996)

    and measured the step response of the system as well, with three
    different Peltier junctions between the point we were stabilising and
    the heat sink.

    It's discussed in the third page of the paper. It does get a bit messy,
    but it is do-able.

    --
    Bill Sloman, Sydney

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From piglet@21:1/5 to Pimpom on Mon Sep 16 17:46:29 2024
    Pimpom <Pimpom@invalid.invalid> wrote:
    I'm going to use a standard 7812 TO-220 regulator on a single-sided 1 oz board with the dissipation varying as below:

    - Idle at 120-150mW
    - 0.5W for 1-5 minutes at irregular intervals
    - Up to 4W for 1 second at the start of each 0.5W phase

    The interval between the 1-5-minute periods is variable and may be 1 to
    10 minutes.

    The ground pin is soldered to ~2 sq.in. of copper on the PCB.

    Options:
    1) As described. No extra heatsinking.
    2) Mount it on a small Al heatsink.
    3) Place the regulator horizontally on the underside and bolt it to the copper.

    Tamb = ~35ºC max

    Do you think option 1) is enough? Or should I go for 2) or 3)?


    You mentioned single sided board so I would be wary of just having the regulator standing straight up anchored only by the legs. Without plated through holes a s/s board joint cannot reliably support the weight of a
    TO220 package if the unit is dropped or shaken. My preference would be to
    screw it down to board if only for mechanical reasons-then the bolt
    hardware and area of copper underneath provide a little bit of extra heat-sinking it also gives more allowance against someone installing the
    unit next to a furnace or somewhere hotter than 35degC

    --
    piglet

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to erichpwagner@hotmail.com on Mon Sep 16 11:10:56 2024
    On Mon, 16 Sep 2024 17:46:29 -0000 (UTC), piglet
    <erichpwagner@hotmail.com> wrote:

    Pimpom <Pimpom@invalid.invalid> wrote:
    I'm going to use a standard 7812 TO-220 regulator on a single-sided 1 oz
    board with the dissipation varying as below:

    - Idle at 120-150mW
    - 0.5W for 1-5 minutes at irregular intervals
    - Up to 4W for 1 second at the start of each 0.5W phase

    The interval between the 1-5-minute periods is variable and may be 1 to
    10 minutes.

    The ground pin is soldered to ~2 sq.in. of copper on the PCB.

    Options:
    1) As described. No extra heatsinking.
    2) Mount it on a small Al heatsink.
    3) Place the regulator horizontally on the underside and bolt it to the
    copper.

    Tamb = ~35C max

    Do you think option 1) is enough? Or should I go for 2) or 3)?


    You mentioned single sided board so I would be wary of just having the >regulator standing straight up anchored only by the legs. Without plated >through holes a s/s board joint cannot reliably support the weight of a
    TO220 package if the unit is dropped or shaken. My preference would be to >screw it down to board if only for mechanical reasons-then the bolt
    hardware and area of copper underneath provide a little bit of extra >heat-sinking it also gives more allowance against someone installing the
    unit next to a furnace or somewhere hotter than 35degC

    I think he has a 10:1 or so thermal safety margin. Most fets are rated
    for 150 or 175 degC max Tj, and can stand a lot more in real life.

    I agree about the standup vibration issue. Why not use a surface-mount
    dpak?

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jasen Betts@21:1/5 to john larkin on Tue Sep 17 05:02:13 2024
    On 2024-09-16, john larkin <jl@650pot.com> wrote:
    On Mon, 16 Sep 2024 17:46:29 -0000 (UTC), piglet
    <erichpwagner@hotmail.com> wrote:

    Pimpom <Pimpom@invalid.invalid> wrote:
    I'm going to use a standard 7812 TO-220 regulator on a single-sided 1 oz >>> board with the dissipation varying as below:

    - Idle at 120-150mW
    - 0.5W for 1-5 minutes at irregular intervals
    - Up to 4W for 1 second at the start of each 0.5W phase

    The interval between the 1-5-minute periods is variable and may be 1 to
    10 minutes.

    The ground pin is soldered to ~2 sq.in. of copper on the PCB.

    Options:
    1) As described. No extra heatsinking.
    2) Mount it on a small Al heatsink.
    3) Place the regulator horizontally on the underside and bolt it to the
    copper.

    Tamb = ~35ºC max

    Do you think option 1) is enough? Or should I go for 2) or 3)?


    You mentioned single sided board so I would be wary of just having the >>regulator standing straight up anchored only by the legs. Without plated >>through holes a s/s board joint cannot reliably support the weight of a >>TO220 package if the unit is dropped or shaken. My preference would be to >>screw it down to board if only for mechanical reasons-then the bolt >>hardware and area of copper underneath provide a little bit of extra >>heat-sinking it also gives more allowance against someone installing the >>unit next to a furnace or somewhere hotter than 35degC

    I think he has a 10:1 or so thermal safety margin. Most fets are rated
    for 150 or 175 degC max Tj, and can stand a lot more in real life.

    78xx is bipolar internallly and goes into thermal limiting at TJ of 125°C

    But yeah, still losts of headroom in this application.

    --
    Jasen.
    🇺🇦 Слава Україні

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Pimpom@21:1/5 to piglet on Wed Sep 18 00:03:05 2024
    On 16-09-2024 11:16 pm, piglet wrote:
    Pimpom <Pimpom@invalid.invalid> wrote:
    I'm going to use a standard 7812 TO-220 regulator on a single-sided 1 oz
    board with the dissipation varying as below:

    - Idle at 120-150mW
    - 0.5W for 1-5 minutes at irregular intervals
    - Up to 4W for 1 second at the start of each 0.5W phase

    The interval between the 1-5-minute periods is variable and may be 1 to
    10 minutes.

    The ground pin is soldered to ~2 sq.in. of copper on the PCB.

    Options:
    1) As described. No extra heatsinking.
    2) Mount it on a small Al heatsink.
    3) Place the regulator horizontally on the underside and bolt it to the
    copper.

    Tamb = ~35ºC max

    Do you think option 1) is enough? Or should I go for 2) or 3)?


    You mentioned single sided board so I would be wary of just having the regulator standing straight up anchored only by the legs. Without plated through holes a s/s board joint cannot reliably support the weight of a
    TO220 package if the unit is dropped or shaken. My preference would be to screw it down to board if only for mechanical reasons-then the bolt
    hardware and area of copper underneath provide a little bit of extra heat-sinking it also gives more allowance against someone installing the
    unit next to a furnace or somewhere hotter than 35degC

    Good point. With TO-220s, particularly those without a heatsink, I
    usually pull the middle leg out to form a triangle with the other two,
    and bend them on the copper side for a netter grip. If it's mounted on a heatsink, even a small one, the HS is almost always bolted onto the board.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Pimpom@21:1/5 to Pimpom on Wed Sep 18 00:25:43 2024
    On 18-09-2024 12:12 am, Pimpom wrote:
    On 16-09-2024 11:40 pm, john larkin wrote:


    I agree about the standup vibration issue. Why not use a surface-mount
    dpak?

    I considered using the D2pak version but decided against it. One reason
    is that I live in one of the most remote regions of a third world and we
    have nothing like Digikey here. So I've made it a habit to use only the
    most easily available parts. The D2PAK version of 78xx isn't in that category.

    Forgot to mention that I've decided to place the 7812 on the copper side
    and bolt it directly to the PCB. Changed the layout to accommodate the
    reversed pin orientation.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Pimpom@21:1/5 to john larkin on Wed Sep 18 00:12:09 2024
    On 16-09-2024 11:40 pm, john larkin wrote:
    On Mon, 16 Sep 2024 17:46:29 -0000 (UTC), piglet
    <erichpwagner@hotmail.com> wrote:

    Pimpom <Pimpom@invalid.invalid> wrote:
    I'm going to use a standard 7812 TO-220 regulator on a single-sided 1 oz >>> board with the dissipation varying as below:

    - Idle at 120-150mW
    - 0.5W for 1-5 minutes at irregular intervals
    - Up to 4W for 1 second at the start of each 0.5W phase

    The interval between the 1-5-minute periods is variable and may be 1 to
    10 minutes.

    The ground pin is soldered to ~2 sq.in. of copper on the PCB.

    Options:
    1) As described. No extra heatsinking.
    2) Mount it on a small Al heatsink.
    3) Place the regulator horizontally on the underside and bolt it to the
    copper.

    Tamb = ~35ºC max

    Do you think option 1) is enough? Or should I go for 2) or 3)?


    You mentioned single sided board so I would be wary of just having the
    regulator standing straight up anchored only by the legs. Without plated
    through holes a s/s board joint cannot reliably support the weight of a
    TO220 package if the unit is dropped or shaken. My preference would be to
    screw it down to board if only for mechanical reasons-then the bolt
    hardware and area of copper underneath provide a little bit of extra
    heat-sinking it also gives more allowance against someone installing the
    unit next to a furnace or somewhere hotter than 35degC

    I think he has a 10:1 or so thermal safety margin. Most fets are rated
    for 150 or 175 degC max Tj, and can stand a lot more in real life.

    I agree about the standup vibration issue. Why not use a surface-mount
    dpak?

    I considered using the D2pak version but decided against it. One reason
    is that I live in one of the most remote regions of a third world and we
    have nothing like Digikey here. So I've made it a habit to use only the
    most easily available parts. The D2PAK version of 78xx isn't in that
    category.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jan Panteltje@21:1/5 to Pimpom@invalid.invalid on Wed Sep 18 12:56:49 2024
    On a sunny day (Wed, 18 Sep 2024 00:12:09 +0530) it happened Pimpom <Pimpom@invalid.invalid> wrote in <64kGO.73253$lZG8.16832@fx09.ams1>:

    I considered using the D2pak version but decided against it. One reason
    is that I live in one of the most remote regions of a third world

    Wow I did not know you lived in the USA!

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to All on Wed Sep 18 07:39:47 2024
    On Wed, 18 Sep 2024 12:56:49 GMT, Jan Panteltje <alien@comet.invalid>
    wrote:

    On a sunny day (Wed, 18 Sep 2024 00:12:09 +0530) it happened Pimpom ><Pimpom@invalid.invalid> wrote in <64kGO.73253$lZG8.16832@fx09.ams1>:

    I considered using the D2pak version but decided against it. One reason
    is that I live in one of the most remote regions of a third world

    Wow I did not know you lived in the USA!

    Cheap people make cheap shots.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to All on Wed Sep 18 07:40:46 2024
    On Wed, 18 Sep 2024 00:12:09 +0530, Pimpom <Pimpom@invalid.invalid>
    wrote:

    On 16-09-2024 11:40 pm, john larkin wrote:
    On Mon, 16 Sep 2024 17:46:29 -0000 (UTC), piglet
    <erichpwagner@hotmail.com> wrote:

    Pimpom <Pimpom@invalid.invalid> wrote:
    I'm going to use a standard 7812 TO-220 regulator on a single-sided 1 oz >>>> board with the dissipation varying as below:

    - Idle at 120-150mW
    - 0.5W for 1-5 minutes at irregular intervals
    - Up to 4W for 1 second at the start of each 0.5W phase

    The interval between the 1-5-minute periods is variable and may be 1 to >>>> 10 minutes.

    The ground pin is soldered to ~2 sq.in. of copper on the PCB.

    Options:
    1) As described. No extra heatsinking.
    2) Mount it on a small Al heatsink.
    3) Place the regulator horizontally on the underside and bolt it to the >>>> copper.

    Tamb = ~35C max

    Do you think option 1) is enough? Or should I go for 2) or 3)?


    You mentioned single sided board so I would be wary of just having the
    regulator standing straight up anchored only by the legs. Without plated >>> through holes a s/s board joint cannot reliably support the weight of a
    TO220 package if the unit is dropped or shaken. My preference would be to >>> screw it down to board if only for mechanical reasons-then the bolt
    hardware and area of copper underneath provide a little bit of extra
    heat-sinking it also gives more allowance against someone installing the >>> unit next to a furnace or somewhere hotter than 35degC

    I think he has a 10:1 or so thermal safety margin. Most fets are rated
    for 150 or 175 degC max Tj, and can stand a lot more in real life.

    I agree about the standup vibration issue. Why not use a surface-mount
    dpak?

    I considered using the D2pak version but decided against it. One reason
    is that I live in one of the most remote regions of a third world and we
    have nothing like Digikey here. So I've made it a habit to use only the
    most easily available parts. The D2PAK version of 78xx isn't in that >category.

    Can you receive shipments from the USA?

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Bill Sloman@21:1/5 to john larkin on Thu Sep 19 02:07:38 2024
    On 19/09/2024 12:39 am, john larkin wrote:
    On Wed, 18 Sep 2024 12:56:49 GMT, Jan Panteltje <alien@comet.invalid>
    wrote:

    On a sunny day (Wed, 18 Sep 2024 00:12:09 +0530) it happened Pimpom
    <Pimpom@invalid.invalid> wrote in <64kGO.73253$lZG8.16832@fx09.ams1>:

    I considered using the D2pak version but decided against it. One reason
    is that I live in one of the most remote regions of a third world

    Wow I did not know you lived in the USA!

    Cheap people make cheap shots.

    No universal health care makes the USA distinctly third world.

    It's not a cheap defect - health care in the US (when you can get it)
    costs half as much again more than same health care in expensive places
    like German, Switzerland and the Netherlands.

    It showed up in the Covid-19 death rate. 3642 deaths per million isn't
    the worst performance around, but it's surprisingly third world.

    https://www.worldometers.info/coronavirus/

    Having Donald Trump as your president when the pandemic was doing its
    worst didn't help.

    --
    Bill Sloman, Sydney

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jan Panteltje@21:1/5 to JL@gct.com on Thu Sep 19 06:02:25 2024
    On a sunny day (Wed, 18 Sep 2024 07:39:47 -0700) it happened john larkin <JL@gct.com> wrote in <ngplejdkis8l68dgo3cmt9om9p6lrgr2t1@4ax.com>:

    On Wed, 18 Sep 2024 12:56:49 GMT, Jan Panteltje <alien@comet.invalid>
    wrote:

    On a sunny day (Wed, 18 Sep 2024 00:12:09 +0530) it happened Pimpom >><Pimpom@invalid.invalid> wrote in <64kGO.73253$lZG8.16832@fx09.ams1>:

    I considered using the D2pak version but decided against it. One reason >>>is that I live in one of the most remote regions of a third world

    Wow I did not know you lived in the USA!

    Cheap people make cheap shots.

    Some kill

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From LM@21:1/5 to All on Mon Sep 23 22:57:29 2024
    On Sun, 15 Sep 2024 16:58:01 +0530, Pimpom <Pimpom@invalid.invalid>
    wrote:

    I'm going to use a standard 7812 TO-220 regulator on a single-sided 1 oz >board with the dissipation varying as below:

    - Idle at 120-150mW
    - 0.5W for 1-5 minutes at irregular intervals
    - Up to 4W for 1 second at the start of each 0.5W phase

    The interval between the 1-5-minute periods is variable and may be 1 to
    10 minutes.

    The ground pin is soldered to ~2 sq.in. of copper on the PCB.

    Options:
    1) As described. No extra heatsinking.
    2) Mount it on a small Al heatsink.
    3) Place the regulator horizontally on the underside and bolt it to the >copper.

    Tamb = ~35C max

    Do you think option 1) is enough? Or should I go for 2) or 3)?
    I would very much try to get a switcher mode replacement for 7812.
    They don't get hot.
    Mouser and Digikey stock them, and probably EBAY and Alibaba too.
    And many others.
    Examples
    TSR 1-24120
    P7812B-1000
    R-78K12-1.0

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)