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'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)?
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.
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)?
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
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
:-)
On 15-09-2024 09:46 pm, john larkin wrote:
On Sun, 15 Sep 2024 16:58:01 +0530, Pimpom <Pimpom@invalid.invalid>Thanks for the input. Calculating heatsink requirement for continuous >dissipation is one thing. Short bursts are another.
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
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.
On 16-09-2024 12:25 am, john larkin wrote:
On Sun, 15 Sep 2024 23:03:09 +0530, Pimpom <Pimpom@invalid.invalid>
wrote:
That's good to know. Even if those data are a bit off, it still leavesThanks 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.
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.
On 15-09-2024 06:11 pm, Martin Brown wrote:
On 15/09/2024 12:28, Pimpom wrote:Thanks. I'm inclined to think that way too. Calculating temerature rise
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.
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.
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)?
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
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.
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
On 16-09-2024 11:40 pm, john larkin wrote:
I considered using the D2pak version but decided against it. One reason
I agree about the standup vibration issue. Why not use a surface-mount
dpak?
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.
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
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!
On 16-09-2024 11:40 pm, john larkin wrote:
On Mon, 16 Sep 2024 17:46:29 -0000 (UTC), pigletI considered using the D2pak version but decided against it. One reason
<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?
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.
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$lZG8.16832@fx09.ams1>:
I considered using the D2pak version but decided against it. One reason
is that I live in one of the most remote regions of a third world
Wow I did not know you lived in the USA!
Cheap people make cheap shots.
On Wed, 18 Sep 2024 12:56:49 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
On a sunny day (Wed, 18 Sep 2024 00:12:09 +0530) it happened Pimpom >><Pimpom@invalid.invalid> wrote in <64kGO.73253$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.
I'm going to use a standard 7812 TO-220 regulator on a single-sided 1 oz >board with the dissipation varying as below:I would very much try to get a switcher mode replacement for 7812.
- 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)?
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