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TEC Cooling

MarioMaster

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They are TEC based but they suck, the plate on top does get cold but it doesn't transfer enough heat from the drink to make a difference
 

c4r0

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Isn't TEC really needed ONLY when you want to stabilize the diode temperature (and thus the wavelength)? If you want to improove cooling you can just use larger heatsink or add a fan and improve thermal connection between the diode and heatsink. I think you should use TEC only when you need to get lower than ambient temperature (which would not be good for a laser diode I think), or when you need to precisely control the temperature of something with electric signal (and using heater is not a good idea ;) ). Am I wrong?
 

billg519

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The simplest TEC controller I can think of uses a mosfet of sufficient current rating for the TEC, a thermistor, and a resistor. The thermistor and resistor (Use a pot for variable settings) form a voltage divider across the mosfet gate. As the thermistor varies in value, more or less voltage goes to the gate, thereby controlling the TEC. Another possibility is a PWM setup where the duty cycle is varied by a thermistor. Sorry I can't be more precise, it's been awhile since I played with TEC.

Bill.
 
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Isn't TEC really needed ONLY when you want to stabilize the diode temperature (and thus the wavelength)? If you want to improove cooling you can just use larger heatsink or add a fan and improve thermal connection between the diode and heatsink. I think you should use TEC only when you need to get lower than ambient temperature (which would not be good for a laser diode I think), or when you need to precisely control the temperature of something with electric signal (and using heater is not a good idea ;) ). Am I wrong?
Temperature tuning is the most important use of a TEC, yes, but laser diodes generally have an absolute maximum temperature of 25-30C. It's very easy for ambient temperatures to exceed this. A TEC is an ideal way ensureing they remain cool.. You don't really want to run your diodes near their max temperature.
 
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I got one from Virtual Village, and I'm wondering how to identify the hot size.


One side of it does say H • C, but I wonder if it means

Hot • Chaud <-- french for hot

or

Hot • Cold?
 

MarioMaster

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It doesn't really matter too much cause if you power a TEC backwards, the cooling and heating sides will be reversed. It won't hurt it. You could power it momentarily with a AA or 9v battery and you'll be able to tell what side is what.
 

Krutz

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i am sure any diode from an optical drive has a temperature limit way above 30°C? more in the 80°C region? absolutely impossible to keep the diode under 30°C, even if it didnt heat up itself, the other components in the drive make the inside warmer than that already..

well, you dont want to cool a diode too much. if the diode is producing 2 watts heat (no small 5.6mm diode from any drive does more than this), you shouldnt put much more than, say, 5 watts to the TEC. TECs are less than 50% efficient, meaning that with 10 watts input, they produce 5 watts of heat by themselfes (!) [or is it even 10 watts?] and have maximum 5 watts "heat-shifting-power", removing 5 watts of heat from the cold side and moving it to the hot side. ..where you end up with a
sum of 10 [or 15?] watt heat to remove!

all numbers badly remembered and half guessed.. check again!

manuel
 

billg519

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Krutz - The diodes may get quite warm in a sled while operating in the drive for their intended purpose. Once we get our hands on them, it's a whole new ball game as we overdrive them as much as we can get away with! The way we use diodes, we need big heatsinks and any other means of cooling, such as TEC, is a big help in some applications. When a diode is run hard, like we do, cooling of course becomes more important.
 

Meatball

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Remember, TECs don't produce any heat on their own, they only MOVE the heat from one plate to the other. TECs can move less heat (watts) than 50% of their input power.
 

Krutz

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Remember, TECs don't produce any heat on their own, they only MOVE the heat from one plate to the other. TECs can move less heat (watts) than 50% of their input power.
you will not be able to "remove" (=move) 10 watt of heat by feeding 10 watt electrical energy into your TEC.

Thermoelectric cooling - Wikipedia, the free encyclopedia
Thermoelectric junctions are generally only around 5–10% as efficient as the ideal refrigerator
another one:

TEC Efficiency - Overclock.net - Overclocking.net
Just as an example, a 437w Qmax peltier device consumes 25a at 24v. In other words, it dissipates 25*24=600 watts of electricity (into heat on the hot side) while only moving 437 watts worth of heat from the cold to hot side.
(..and those guys "work" with TECs routinely)

manuel
 

MarioMaster

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Can you cut these??? Trim to size?
I've successfully cut one in half when I needed a small one for a job, but you have to make sure you keep the circuit intact. All the junctions are in series so if you cut them vertically, you only need to solder one place for a new wire.

Cut them horizontally and you need to reconnect each junction string and make sure you keep the polarity correct, as well as the final connection for the new power wire.
 

Things

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TEC's will generate a little extra heat ontop of what they move, if they didn't, they would be a 100% efficient device, which isn't possible just yet.

Be careful cutting the TEC's, the ceramic is VERY brittle. I have broken one just by trying to get it off a heatsink with a little thermal paste on it!

As for driving it, if you want to be able to set the temperature, and maintain it, you will need a driver with temperature feedback, if you just want to set the temp and leave it, you can use a basic driver like a LM317.

The USB TEC drink coolers are useless. My TEC, drawing 15V @ 4A only just manages to keep a drink cool, 5V @ 500ma, you may be able to keep a drip of water on the TEC cold :p
Some devices actually use multiple USB ports, but IMO it's a waste of USB ports. If you want a computer activated TEC drink cooler, run a line from the 12V output of your computers PSU, it will come on with the computer too obviously, and can supply many amps. TEC's will keep drawing current with a higher voltage, though they won't draw large amounts of current at lower voltages, unlike diodes.

As Mario said, you can test wic side is hot and cold simply by hooking it up to a power source. Reverse polarity on the TEC will just mean the hot and cold sides switch. Also a recommendation, do NOT cool your diodes past dew point, or you will start getting condensation etc on the diode, which will not end too well. If you want to shove the wavelength down, you would need to stick it in an airtight container with no moisture inside at all.
 

Krutz

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..or glue everything in.. provided its a closed can, anyway! there wont be any moisture inside the can, and that little air between the can and the lens shouldnt be critical. if the pins are sealed with glue, it all should work out.. not recommended anyway! :)

thanks for the hint about cutting TECs smaller! wouldnt have thought that..

manuel
 




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