Electronics > Projects, Designs, and Technical Stuff
DC load using a CPU cooler
rob77:
--- Quote from: Spikee on September 17, 2014, 05:46:33 pm ---
--- Quote from: rob77 on September 17, 2014, 05:34:29 pm ---
--- Quote from: Spikee on September 17, 2014, 04:42:56 pm ---It is alive !
It has a few bugs, i placed the 3d model facing the wrong way. So to fix the pinout i needed to mount the heatsink and mosfets on the bottom.
Also to rise the mosfets up it is advisable to use some discard able 0805 resistors under it so it rises the mosfet by around 1mm.
With some tweaking it is definitely something that is doable.
--- End quote ---
where are your current sensing resistors ? even if you use 0R1 then it's 2.5W at 5Amps - can't see any resistors capable of 2.5W on your board ;)
and sorry , but i doubt it's alive - half of the parts are missing yet :D
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There are two big ones on the bottom =)
mouser.com/Search/ProductDetail.aspx?R=WSL36372L000FEA
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2milliOhm ? :scared: what op-amp are you using ? 1mV input offset means half an Amp error with a 0R002 current sensing resistor.
Spikee:
The INA225 monitors each current shunt.
but keep in mind that this is still a prototype. Parts might change.
kc9qvl:
That looks very nice.
Mine is very meager compared. How many watts can it dissipate?
Spikee:
with a better heatsink 300-350w should be possible. With the current smal one only around 150-200w.
Nerull:
--- Quote from: max_torque on September 13, 2014, 12:32:04 pm ---Thing is, a CPU cooler is doing a specific job, which is to MOVE a high heat flux heat from a very small area, and then reject it to the ambient. A typical DC load, to handle a high power dissipation will need multiple parallel power devices, and so you don't have such a small area / concentrated heat source. Also, in modern computer design, the issue is packaging the heat transfer device into an ever smaller physical space, again, unlikely to be an issue with a typical bench top DC load.
And ultimately, you have to reject that heat to the ambient atmosphere, which for a high power DC load requires a lot of surface area or a lot of fast moving air, as it is (should be) continuously rated. This means either a large heatsink or a powerful fan.
I suspect that while CPU coolers have nice low thermal transfer co-efficient, they actually don't have amazing total heat rejection values (because the CPU is still a relatively low power device (it gets "hot" because it is so compact!)
For my DC load i used a nice big heatsink, placed the power devices nicely spread out on it, and used two powerful speed controlled server cooling fans to blow a LOT of air past it. This manages pretty much 300W continuous in an 30degC ambient.
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With CPUs out there outputting more than 200W of heat under load and gamers who can't stand to see their CPUs top 40C, I'm sure there are heatsinks out there that can handle that.
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