[time-nuts] Cycling of Peltier junction

Jerome Peters jpeters at nvidia.com
Thu Sep 9 22:29:12 UTC 2010


Wow, So many people have helped - Thanks!

I see your point, it can be done without changing the polarity, just control how much heat is carried away... very interesting.

Regards,
Jerome

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of paul swed
Sent: Thursday, September 09, 2010 2:55 PM
To: jfor at quik.com; Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Cycling of Peltier junction

Can you just close the system and let the item self heat.
Then you only ever have a cooling problem.
Seems I am familiar with a very large computer manufacture who does it that
way.

On Thu, Sep 9, 2010 at 5:14 PM, J. Forster <jfor at quik.com> wrote:

> Peltier devices have been used as temperature control elements for
> decades. I've never heard of fatigue failures, but, if I were designing a
> chamber as you suggest, I'd try to keep the temperature differential
> across the TE element under maybe 15 to 20F. The harder you push it, the
> greater the stress.
>
> Also, the heat pumping power falls dramatically as the delta-T increases
> and it's a situation of rapidly deminishing returns.
>
> I'd not worry much about ramping the drive.
>
> FWIW,
>
> -John
>
> ===============
>
>
>
> > Does anybody know about using the same Peltier junction for both heating
> > and cooling?
> > I'm concerned about thermal/mechanical shock when changing the polarity
> > back-n-forth between hot and cold.  Maybe there needs to be a controlled
> > ramp, if so then how do I figure out the rate?
> >
> > Why:
> > I'm in the process of building a small environmental chamber for my home
> > lab. The volume is ~30 liter, target temp range of 0C to 60C.  For the
> > cooling side I am using water circulation (radiator, pump, reservoir &
> > water block) and Peltier junctions.  At first I was planning to have two
> > separate systems, one for heating and one for cooling, but then I got to
> > thinking that using just the water and Peltier could be used for both.  I
> > will be using a PID for temp control, and two TEC1-12726 Peltier
> Qcmax(w)=
> > ~240 △T =0j
> >
> >
> > Regards,
> > Jerome
> >
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