Peltier ramp up / down time

Discussion in 'The Projects Forum' started by sheepdog, Oct 29, 2015.

  1. sheepdog

    Thread Starter Member

    Jan 26, 2009
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    Hi i have a project that on occasions needs the peltier to ramp down and then ramp up (not instantly) using pwm The time factor for the ramping period is not critical over a period of 10 minutes is no problem. Has anybody an idea of a period i could use to prevent temperature change shock to the peltier, for example would dropping 1 duty cycle every 1 minute be detrimental to the peltier.
    Many thanks for any thoughts on this
     
  2. OBW0549

    Distinguished Member

    Mar 2, 2015
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    I'm no expert on Peltier devices, but from what I've read my understanding is you do NOT want to drive them from a PWM signal because it makes them extremely inefficient. The PWM signal should be filtered instead, so that the Peltier device receives a variable DC signal with little ripple.

    That said, I think the answer to your question is, "it depends." Over what temperature range are you ramping up and down? How much thermal mass is being controlled? I imagine that several degrees Celsius per minute would not be a problem, but beyond that I couldn't say.

    Linear Technology, Inc. has a pretty good application note on using Peltier coolers; it might contain some good information.
     
  3. sheepdog

    Thread Starter Member

    Jan 26, 2009
    12
    0
    Thanks for the reply, i am using the pwm to control a buck converter with low ripple, i was just pondering over what time period in ramping down the duty cycle becomes damaging to the peltier. I have read that a manufacturer tested a device between 100 deg c to 30 deg c and then back up again over a 15 minute period and achieved iirc 16 million cycles before performance issues arose
     
  4. OBW0549

    Distinguished Member

    Mar 2, 2015
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    That sounds about right, though I don't know how much faster than that you could go.
     
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