peltier component cooling

[jamie1107]

hi
i dont profess to be amasing with electronics i have built a few gainclones tube amps and a megasquirt but today i saw on ebay someone selling small peltier plates and peltier cpu coolers for pc s and it struck me that as one of the main problems amp builders face is getting rid of heat maybe this might work
has anyone used this system or does anyone have anyideas on the signal noise a peltier element might produce or if they can be directly coupled to the heat sinks
just a thought

[dave_gerecke]

Hey Jamie, If you do a search of the site for peltier, you will find discussions on this. The peltier won't really do anything but use more power. While it may move thermal energy (heat) from one place to another, it doesn't eliminate heat. That would violate the laws of thermodynamics. Because of this, you would need a heatsink on the opposite side of the peltier from where you mount the active device, in this case your chip amp device.

Peace,

Dave

[TheMG]

Using a TEC would decrease the temperature of the components you're cooling, but since the TEC also generates it's own heat, you'd need an even larger heat sink!

There are a few solutions to provide better cooling for your amp:

-larger heat sink

-mounting the heat sink externally as part of the chassis rather than putting it inside the chassis

-using a fan for supplemental cooling, you could add a circuit to only turn on the fan when the temperature is high in order to eliminate fan noise problems

-water cooling, no reason why that shouldn't work

-higher efficiency amplifier design, this could be going to class D, but there are also ways to increase the efficiency of a class A/B circuit. The data sheets for some chip-amps include application notes on how to increase efficiency.

[tiltedhalo]

I had considered using a TEC with water cooling for a high power amp, but to keep the transistor's at a constant temp the TEC or TEC's will consume almost as much as the amp, to remove 200W of heat you need 200+ watts of TEC, can get expensive very quickly and will eat allot of juice.

[EWorkshop1708]

I own a peltier, and they run HOT!

You need a BIG heatsink AND a fan to keep them cool.

But you can freeze water in seconds with one! They are really cool.

[MotoMan_Yz400]

Heatsinks run more efficient the hotter they get. Well it's more like greater the difference between heatsink temp and air temp. So I was thinking that a peltier device or TEC would heat the heatsink up to a much higher temp (allowing the sink to get rid of the heat better) and then the chips would run cooler.

[TheMG]

Don't forget that TECs have a maximum temperature differential (noted in the datasheet). So the hotter the hot side, the warmer the cold side will be.

Also, keep in mind that TECs are semiconductors, so you have to be aware of it's temperature. Can't let it get too hot.

Yes, a heat sink will dissipate more heat energy when it's hotter, but what you have to look at is the overall efficiency of the system. Weight out the pros and the cons.

Generally, if you're wanting too cool components dissipating 100W of heat, you'll need at least a 100W TEC. You're effectively doubling the amount of heat the heat sink need to dissipate, and you need to keep the TEC running at a safe temperature, same maximum temperature you'd want your transistors to run at.

Pros: cooler running components (not always!).

Cons: very high power usage, larger heat sink required, output devices may fry if a TEC fails.

Up to you to decide, but I think the cons outweigh the pros. Better off using water cooling or heat pipes if you want plenty of cooling ability.

[EWorkshop1708]

Once the hot side of a TEC is over 120 degrees F, the cold side is not very cold anymore. It's IMPORTANT to keep them cool.

For 12V Thermoelectric coolers, they use a large heatsink that is fan cooled to keep the temp down, so your food and drinks are colder.

You'd be better off running the transistors (or chipamp) scalding hot, then to have to worry about the temp of a TEC (BTW transistors can take higher temps)

Also, transistors aren't as temp-critical as a computer CPU. I've had the best luck overclocking a CPU when it's under 100 degrees F. For that, I can see why a TEC is useful. Transistors, however, can run really hot and work fine.

I measured the temp under full load of a 100w/ch STK4231 chip amp, and the heatsink was over 170 degrees F with a fan!!! Of course, my DIY amps NEVER run near that hot!!!

But just to make the point, you can run transistors/chips hotter than a TEC.

Now, to push the envelope even further, you could TEC cool an amp, then water-cool the TEC and have the hot radiator mounted remotely far away from amp components. The amp would run cool, and you would have to find a good spot for the radiator to dump all that heat (A LOT) You'd need some sort of temp-shutoff incase of any fault conditions. Just more ideas - the beauty of DIY.

[TheMG]

Originally posted by EWorkshop1708
I measured the temp under full load of a 100w/ch STK4231 chip amp, and the heatsink was over 170 degrees F with a fan!!! Of course, my DIY amps NEVER run near that hot!!!

Similar experience with an amp I pulled from a broken mini-system (CD player was kaput, rest was ok). Is an STK4221, just for fun I cranked it with some low-frequency tones to see at which point the fan would kick in, turns out it doesn't kick in until the heat sink gets way too hot to touch! No wonder they had a plastic guard over the heat sink.

[EWorkshop1708]

It's a shame that a chip amp design could be really good, but they go cheap on the heatsink. No wonder you end up replacing those STK modules sooner or later. The STK amp I have doesn't run the fan until the volume is 1/2 or more. So if you have to volume turned down, it runs really hot.

IMO a heatsink should never be too hot to touch.