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Thread: The big TEC driver thread!

  1. #41
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    A question?
    Would a PWM power supply work with the larger TEC's 100watt+?

  2. #42
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    It might work .
    Last edited by ionlaser555; 01-21-2014 at 08:14.
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  3. #43
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    Quote Originally Posted by dar303 View Post
    Thats a nice large-scale setup! What laser have you tried it with?
    So far, none. I just started building a piece of universal linear Nd:YAG resonator to play with 659nm, 476nm & 532nm SHG emission. In case of 532nm my rough expectations are between 1-3 Watts. I'm curious what effeciency awaits me at these more exotic wavelengths
    Piotr.K

  4. #44
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    Quote Originally Posted by tocket View Post
    I could imagine building a TEC controller using a microcontroller. Might seem overkill, but considering how many analog inputs and outputs they typically have it might be simpler as you can one to control all TECs. Could it be as simple as an arduino (6 analog in and 14 digital out [6 with PWM]) and an H-bridge and thermistor for each TEC? You could control the TECs for at least 6 lasers with that.

    Someone else would have to design the circuit, but I could probably write the code.
    Someone has already written a PID loop for the Arduino, their application was an Espresso machine.

    http://www.arduino.cc/playground/Mai...PIDForEspresso

    Most of the work is done already.

    For DPPS, I have been considering using an Arduino/ATMega with a H-Bridge on bipolar rails to provide both cooling and heating (for those in colder climates) as required (TEC pump heat either direction based on polarity). I have not seen anything like this out there yet. I would not use a thermister either, I rather use digital sensors that read in degrees kelvin. The readings are absolute and the same in every device.

    If anyone is interested , I can knock up a prototype in a few hours. I have the Arduino, H-Bridge and spare TEC's in my parts bin.

    Quote Originally Posted by dar303 View Post
    Does anyone have good sources for small TEC's they want to share?
    The ones on ebay are usually big ones, 40x40 mm or so.
    I get mine from Farnell/Newark.

    http://au.farnell.com/jsp/search/bro...0001%2B1002416

    They do small ones, 11, 15, 20mm and up.

    Wayne.
    Last edited by dnar; 08-17-2010 at 01:28. Reason: Added answer to dar303
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  5. #45
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    There's actually good code for PID in one of the AVR appnotes; check out appnote AVR221. I was working on building such a device when I was rudely interrupted by breaking my arm.

  6. #46
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    Quote Originally Posted by heroic View Post
    There's actually good code for PID in one of the AVR appnotes; check out appnote AVR221. I was working on building such a device when I was rudely interrupted by breaking my arm.
    Yeah, I have read that app note before.

    I was thinking that if the sensor was on the laser side of the heatsink, a PI loop would suffice due to the relative thermal delay from the heatsink. But I have read others (in previous posts) indicate placing the sensor on the TEC side of the heatsink. Doing so would be better with PID. I do not understand why they do this. Surely the objective is to maintain thermal stability of the device you are regulating, ie. the laser!

    Sorry to hear about your arm. One hand typing presently?

    Wayne.
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  7. #47
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    Quote Originally Posted by dnar View Post
    If anyone is interested , I can knock up a prototype in a few hours. I have the Arduino, H-Bridge and spare TEC's in my parts bin.
    I'm all ears Mabe it could be a Heroic, Dnar team effort Keen as to have a versatile, bipolar TEC controller.. I could lend a hand in the way of PCB design
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  8. #48
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    Quote Originally Posted by dave View Post
    I'm all ears Mabe it could be a Heroic, Dnar team effort Keen as to have a versatile, bipolar TEC controller.. I could lend a hand in the way of PCB design
    Ok, I have spare time at the moment, on leave and starting a new job in Sept. My planned work trip to Canberra has been delayed for 2 weeks time so I will breadboard a circuit, write some code and I already have heatsinks with TEC's laying around from past projects.

    I would normally layout the PCB myself using Altium, but I am not at work. I might be able to dig up my old copy of Autotrax... It might be easier and quicker if I flick you the final schematic with netlist, you can route the board. Who do you use for PCB's? I use Precision in Melbourne, used to use Entech.

    All I need to simulate is a load device, in fact I can use a 100mW DPPS I have in my parts bin.

    Stay tuned.
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  9. #49
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    I have a hot copy of DXP2002 that has served me pretty well.

    I'm a bit ashamed to say I have only got boards made locally once, all times after, either a mob in Malaysia, or China.. Cant beat China for price, but it doesn't really help local business.
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  10. #50
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    Quote Originally Posted by dave View Post
    I have a hot copy of DXP2002 that has served me pretty well.

    I'm a bit ashamed to say I have only got boards made locally once, all times after, either a mob in Malaysia, or China.. Cant beat China for price, but it doesn't really help local business.
    I know what your saying. Even Entech/Precision will tell they can't match the quality especially on 6+ layer boards. In fact, unless you specify "Made in Aus" ship most of their boards to China to partner plants.

    I design sensitive application electronics (can't say what) that simply can and will not leave Aus soil. Most of it 6 layer. I can't go to 8 layer simply because we don't do it in Aus! Some times this makes board routing a pain with dense designs. It is restricting.

    I'll flick you a schematic in the next few days. A few questions:


    1. What range of TEC power ratings are typically required (trying to keep the H-bridge small like a SN754410 rather than something like LM298. I have both, the SN754410 is only rated 1amp, the LM298 4amps. I like these, their robust and TTL drive.
    2. Any idea of the max W/oC we are expecting? This will determine power and voltage.
    3. What is the preferred power source? SMPSU or linear?

    Cheers.

    Wayne.
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