Electronics > Beginners
DC dummy load circuit calibration
VEGETA:
As for heatsinks, I still didn't get them from my friend but they will arrive soon.
I wonder if something like this works:
https://alutronic.com/products/heat-sink-pcb-mounting/for-multiple-mounting/69/pr134/75/se/m3?c=1356
or one of these for each mosfet: https://www.aliexpress.com/item/5pcs-lot-38x34x12-8mm-TO220-TO-220-heatsink-heat-sink-radiator-for-IC-triode-7805/32622932747.html
without fan cooling? with fan cooling?
Let's say one day this project got better and I want to try and make small quantity to sell, then I would need standard heatsinks that I could buy (not cut them).
Remember that this is the case: https://www.aliexpress.com/item/Black-Extruded-Aluminum-Enclosures-PCB-Instrument-Electronic-Project-Box-Case-100x76x35mm/32813597400.html?spm=a2g0s.9042311.0.0.27424c4d0tvfpY
it is very compact let me tell you but I do like it. That heatsink fits perfectly at the back of this case. If so, then fan cooling might be a good future addition especially if we could move the heatsink inside (get a slightly bigger case).
In the mean time, dreams aside... I am getting ready to do the PCB in next week.
ledtester:
You'll want to use a fan. It will greatly enhance the dissipative ability of the heat sink which means you can use a smaller heat sink.
Have a look at how some commercial loads are built:
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- https://item.taobao.com/item.htm?spm=a312a.7700824.w4004-1173757744.2.51092a79IJ04Xg&id=567150768124
That arrangement of heat sink and fan seems to work well.
VEGETA:
How about putting 4 heatsinks (to-220 one version) so one per mosfet? putting them near each other (mosfets facing each other) then put a fan at back panel to suck all air out. I guess this is the best I can do for now or the other solution is to put one big heatsink outside which would be ugly.
The 4 heatsinks would be inside the case while the fan could be inside or outside. I could make holes in back panel so that air could escape and thus we get a completely enclosed project. I still don't have what it takes to decide since I didn't test anything.
According to this project, we would have 15 watts per mosfet which means the heatsink must dissipate 15 watts. I guess these ones linked above can do the job without a fan so with a fan it should be much better.
The bummer is that these Chinese ones do not have the temperature coefficient or even a datasheet of some sort!
VEGETA:
I found these ones which can fit inside the case: https://www.aliexpress.com/item/High-quality-3010s-30MM-30-x-30-x-10MM-12V-2Pin-DC-Cooler-Small-Cooling/32603431500.html
Putting 2 of this one should be nice right? they come in 12 and 5v version so I don't know maybe 12v is better. The 0.13A consumption is too much though.
VEGETA:
The best one I found is this: https://eu.mouser.com/ProductDetail/Ohmite/FA-T220-64E?qs=sGAEpiMZZMttgyDkZ5WiumlCfl50RTwzVA%252bY4U4BtvA%3d
it is 3 degrees per watt which means 3x15 = 45 degrees only. Say ambient is 30 -> 30+45 = 75 degrees without a fan! However they are pricey and I won't find them on Aliexpress so shipping to Jordan gonna be too much.
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