TEC Control

[Ewok85]

There are some TEC kits out that have controllers which keep the temperature at around ambient, meaning you use less power when the PC is idling, and get maximum cooling when you need it.

This post here gave interested me -
Mean Well SD-50A-12 DC-DC Converter (this?)
Digital LED Volt & Amp Meter w/Shunt on TEC Power Supply Output

What are these for? How much control does this give?

I've been thinking - if you could hook up a themal sensor and PWM to a microcontroller, do you think it would be possible to make it more or less automatic?

[manicdan]

that powersupply in the link is only gonna give off 50W, when you would need probably the 320w one if u plan to use a "standard" tec, aka the most popular one.

they do have the ability to modify the voltage going out from 9 to 15V giving you less to more when you need it.

in the link to the forum post i see 2 psu, one 600w meanwell and one 50w, i think the 50w is for the pump to make it work harder, and the 600 is 24v output and it looks like he will be running his tec at 19v

[Ewok85]

The 600W 24V Meanwell has only 5% downwards voltage adjustment - thats 22V at best. Its interesting that he is running at 20 because as far as I know its not possible without having something else there to make adjustments.

What I'm ultimately wanting is a control system similar to the Coolit Freezone - a controller that uses a thermister to take temperature readings and control TEC output (cooling) to keep it at an optimal temperature without having to use too much electricity.

[onewecallgod]

Originally Posted by Ewok85

I've been thinking - if you could hook up a themal sensor and PWM to a microcontroller, do you think it would be possible to make it more or less automatic?

Of course it's possible. The real question is whether or not you know enough about digital design to build the circuit.

[Ewok85]

Nowhere near enough - but I've seen people who do know much, much more than me.

Commercial controllers exist, but they aren't cheap and the feature set is overkill for what I want.

[manicdan]

you could actually do something in a less logical way but might be alot easier

instead of controlling the power to the tecs you get a custom fan controller and have it lower the fan speed based on temp, so as the temp goes too low it decides to take less heat out of the system preventing it from getting any colder. it would be alot easier to find a thermometer to mod with a resistor to give off fake readings that the controller likes, than to make your own circuit.

[Ewok85]

Originally Posted by manicdan

instead of controlling the power to the tecs you get a custom fan controller and have it lower the fan speed based on temp, so as the temp goes too low it decides to take less heat out of the system preventing it from getting any colder. it would be alot easier to find a thermometer to mod with a resistor to give off fake readings that the controller likes, than to make your own circuit.

I'm not sure what you mean here.

The power supply to the TEC gives out a constant unchangable 24V, there is currently no control of any sort involved.

Unless you mean I lower the fan speed on the rads, which will simply heat up the water cooling loop which is a very backwards way of controlling the TEC, but an interesting idea non-the-less

By dropping the voltage going to the TEC I can at the same time drop the fan speeds on the rad, a win-win.

Something like the freezone coolit has would be perfect, its just a matter of scale...

[potseeker]

I have also been looking for a more automatic temp control for my chiller and what I have found as far as commercial controllers would be to expensive for me because I need to handle about 45 amps so I would need multiple units I believe its good for 12.5 amps
http://www.mcshaneinc.com/html/5C7-550.html the only other solution I've been able to come up with is a pwm dc motor speed controller they can be found on ebay fairly cheap the one I'm looking at will handle 80 amps for about $100...you can use a microcontroller like basic stamp 2 and a thermal sensor but you would have to build a circuit and learn the programing code... my eight tec's are air cooled so fan control could also be a option for me but it wouldn't reduce power useage...

[manicdan]

thats exactly what i meant ewok. start with just controling the fans, it might be possible to download a program that lets you adjust the fan speeds for ones plugged into your motherboard and set a certain voltage based on heat. or do a search for people who wanted to have software custom control fan speeds, and see what you find.

when you compare cost, think about how much more expensive it is to buy a custom voltage controller for a couple hundred watts, lets say 100$ more. then think about how much more your electric bill we be up by, and how long it will take to spend the same amount. 100 extra watts on 8 hours a day at 13cents per Kw hour. lets just call it 10cents a day extra to not be able to turn down the power of the tecs.

[Ewok85]

Its not savings on my electricity bill that I'm looking for, its peace of mind and security.

By controlling the pelts voltage I can stop it overcooling, which also makes it overheat on the opposite side. By keeping it at a lower level when it isn't required I extend the life of the pelt, as well as the power supply, by not stressing them unneededly. Lowering fan speeds will mean the pelt is strained and I'll just be killing it.

Originally Posted by potseeker

I have also been looking for a more automatic temp control for my chiller and what I have found as far as commercial controllers would be to expensive for me because I need to handle about 45 amps so I would need multiple units I believe its good for 12.5 amps
http://www.mcshaneinc.com/html/5C7-550.html

Yeah, I've seen them too. They aren't all that complex, and would be fairly cheap if you bought the parts yourself, its just finding someone who is able to design the circuit.

This is apparently a good start, its just scaling it up to 25A (or in your case 45A ) that is the problem.

http://www.edn.com/archives/1994/102794/22di4.htm

the only other solution I've been able to come up with is a pwm dc motor speed controller they can be found on ebay fairly cheap the one I'm looking at will handle 80 amps for about $100...you can use a microcontroller like basic stamp 2 and a thermal sensor but you would have to build a circuit and learn the programing code... my eight tec's are air cooled so fan control could also be a option for me but it wouldn't reduce power useage...

You need to be careful, the frequency needs to be at least 500Hz or you might damage the pelts.

[manicdan]

tecs are cheap, the they should last quite some time without a problem. just by lowering the voltage from 12 to 10 with the meanwell powersupply should give you enough of a reduction to keep them happy. and push it up to 14v when you wish to overclock.

in general a peltier cooling system is not ideal for a day to day use computer.

[Ewok85]

I'll be using a 62mm 437W pelt, which goes for about $50 a hit. Thats not cheap...

The power supply is 24V with 10%/-5% control, which is not enough for being able to control it effectivly.

[manicdan]

one really stupid thing about them is the wires going into the tecs are very stiff and its easy to break them off, thats the only way ive had any break on me. and yes that tec is one of the most expensive and if your worried about condensation or overcooling, then your using the wrong one

[Ewok85]

I having my cake and I'll figure out how to eat it even it it means smothering my face in delicious moist cake

Peltier are not the most efficient things out there, but it doesn't mean they don't do the job, and do it **** well when you get it right. Lack of control is a huge factor in this. The circuit at edn.com looks alright, I'm just working with someone to scale it up, then I'll build one and let you know

[manicdan]

what kind of temps are you looking to keep it at?

[Ewok85]

Depends on what temp it can hold under full load, but at idle I would like it to be around 20~25C or so.

[manicdan]

im gonna pull some number out of no where but they should give you an idea

the pelt can move 400 watts with at 60c delta, those are close but not exacts
if the cpu is 100 watts then the cold side will be 45c colder than the hot side. if you can keep your water temps down, IE 45c or less, then your cpu will be at 0c on load. and about -10c idle

if your just looking for a pelt to keep your cpu a bit below ambient than aim about 50% higher than your cpus output power, so 172watt peltier would suit you fine for a cpu pushing 100-125 watts.

find out how much power your cpu is using, sandra should do just fine if your are familiar with it

[Ewok85]

Can't see an overclocked quad core put out a mere 120W of heat

But you are being very helpful. Do you know how to determine possible CPU heat output?

[manicdan]

download sisoft sandra

its a program that looks at everything and can benchmark almost anything aswell
run the cpu arithmetic benchmark and at the bottom scroll through till you see one mention heat output

[Ewok85]

Cheers

My current processor is 100W, and an un-overclocked quad core Intel looks to be about 130W which would scale to close to 150~160 when clocked to max.