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I am testing DRV8840 circuit in my setup as a 12V, 3amp peltier controller.

And there are 3 temperature set points : 25, 30, 37 celcius.

Hardware configuration done so far as follows:

schematics

Trial 1 :

purpose: heating of peltier from 25 to 37 celcius Enable = Logic 1 (5V), Phase = logic 1, decay = 1 R Sense = 0
observation: initial temp 30 and reached 37 after 5 mins ( ok as per our requirement)

Trial 2 :

purpose: cooling of peltier from set point 37 to 25 celcius , Enable = logic 1, phase = logic 0, decay = 1 , R sense = 0, observation : taking 30+ mins for reaching required set point 25 celcius from 37 celcius

Trial 3

purpose: cooling from 37 to 25 with driver off, Enable = logic 0 observation: 30+ mins for reaching 30+ mins for 25 setpoint from 37 is too much , 15 mins waiting time is ok.

For heating Phase pin status = Logic "1" and for cooling phase pin = Logic "0"

So can anyone suggest why cooling taking so much time 30+ mins and way to do fast cooling? (15-20 mins duration ok)

Techknowlogic
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  • Heat transfer effectiveness for cooling is improved by more current and air speed over heatsink to remove heat from hot side with insulation to block ambient heat. – Tony Stewart EE75 Oct 26 '17 at 07:28
  • ok. How I can isolate ambient heat? Peltier block is inside cabinet hence isolated from ambient. – Techknowlogic Oct 26 '17 at 08:17
  • How well do you remove heat when cooling? and what is the thermal resistance and heat mass of interior? – Tony Stewart EE75 Oct 26 '17 at 08:34
  • are you using the PWM feature? Don't, for Peltiers. Do, for motors. – Neil_UK Oct 26 '17 at 08:43
  • I am not using PWM, I am switching "Phase" pin from 1 to o and vice versa for heating /cooling using H bridge concept. – Techknowlogic Oct 26 '17 at 09:06
  • Why do you need a H-bridge? You need just one transistor, not 4. – Marko Buršič Oct 26 '17 at 11:40
  • I need heating as well as cooling, so h bridge used. – Techknowlogic Oct 26 '17 at 12:16
  • No way, the peltier does not work as you might think. You need to physically swap the cell surfaces, not the polarity. – Marko Buršič Oct 26 '17 at 16:22
  • @ Marko Thanks for reply. Can you suggest how to achieve cooling then ? – Techknowlogic Oct 26 '17 at 17:52
  • @MarkoBuršič Peltiers are indeed reversible, and reversing the voltage will change the direction of heating/cooling. I realize this is an old post, but the chip you use here seem to be using PWM, which according to what I've read so far isn't good for peltiers. See https://electronics.stackexchange.com/a/567390/122603 The rate of heating/cooling depends on the thermal mass of what you're trying to cool, and a heatsink is probably required on the hot side when cooling, due to the heat the peltier itself produces. – Oddstr13 Aug 26 '21 at 21:59

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