Using a simple constant current LED driver to drive  Thermoelectric cooler (TEC) - Page 1
Forum section: electronics / projects

author: semir-t
author_rank: Regular Contributor
timestamp: October 09, 2023, 10:00:28 am
content: As subject states, would it be possible to drive the Thermoelectric cooler (TEC) with the simple constant current LED driver. I was thinking about using this one (https://www.diodes.com/assets/Datasheets/AL8843Q.pdf).I would then use the NTC and MCU to implement a PID controller so that I can get desired temperature of the TEC.Would this be possible ?Note: Reason why I am targeting the AL8843 is high output current (3A) and they are cheap. Also I am using this driver on this project for High Power LED as well.

author: Benta
author_rank: Super Contributor
timestamp: October 09, 2023, 01:37:49 pm
content: What is "the TEC"?https://de.wikipedia.org/wiki/TECLife gets easier when avoiding TLAs.

author: magic
author_rank: Super Contributor
timestamp: October 09, 2023, 01:42:14 pm
content: Thermoelectric cooler, presumably.I suppose you can drive them with anything, as long as it's "roughly DC". Pulsed operation is said to damage TECs over time.

author: mawyatt
author_rank: Super Contributor
timestamp: October 09, 2023, 02:06:58 pm
content: Quote from: magic on October 09, 2023, 01:42:14 pmYes, or Peltier Device. TEC is standard nomenclature in technical electronic arenas, both used interchangeably.Best,

author: semir-t
author_rank: Regular Contributor
timestamp: October 09, 2023, 02:19:20 pm
content: Yes, I was referring to Thermoelectric cooler.Thanks.

author: coromonadalix
author_rank: Super Contributor
timestamp: October 09, 2023, 02:28:03 pm
content: would be nice to correct your 1st thread title to reflect that ...

author: mawyatt
author_rank: Super Contributor
timestamp: October 09, 2023, 02:31:43 pm
content: Quote from: magic on October 09, 2023, 01:42:14 pmIs the degradation serious, wasn't aware of this? Our experience with TEC is just in a closed loop servo to control an alumina substrate as a Blackbody thermal reference (8~10 microns), and a "chiller" for cooled medical bandage.Best,

author: magic
author_rank: Super Contributor
timestamp: October 09, 2023, 03:21:07 pm
content: I don't know, but it's common folk wisdom that hysteretic control and perhaps slow PWM wears them out due to repeated mechanical deformations induced by thermal cycling.Chances are that you can get away with it to some extent. I mean, if it worked for you then it worked...

author: TimFox
author_rank: Super Contributor
timestamp: October 09, 2023, 03:34:38 pm
content: I haven't seen that problem in lower-power TECs, but given the different thermal expansion co-efficients of the TEC material itself and the metals bonded to it, I could believe that thermal hysteresis is a stress problem.

author: mawyatt
author_rank: Super Contributor
timestamp: October 09, 2023, 04:18:43 pm
content: In our limited use the TEC just "saw" either a slowly varying DC type voltage (analog closed loop), or On/Off pulsed (very slow cycle time) with a slow (many seconds) temperature ramp up down (limit cycle bang bang servo for chiller). Never heard back on any problems tho, the electronic bandage went into high production so if the TECs were failing we would have heard about this!!Best,

author: mikerj
author_rank: Super Contributor
timestamp: October 09, 2023, 06:09:05 pm
content: Control schemes that causes frequent thermal cycling of the TEC such as thermostatic(bang/bang) should be avoided if possible, this can cause premature failure due to fatigue cracking of the soldered joints attaching the PN junctions to the ceramic substrates. Control schemes that cycle between full off and full on, even at higher frequencies (i.e. raw PWM) should also be avoided if the coefficient of performance of the TEC under less than full load is of any concern.