[sdiy] Peltier Elements

[Czech Martin]

Ian, 
yes, perhaps a hose to the open window with blower could
suck in enough cool air from the outside.
Most of the year the air is below 15C in Germany
(including night time).

Condensation is a big point, for Thermostream experiments
at -40C I had lot of icing problems (outside the stream).

The question is also how low the temperature must be.
If the curves to be observed would be linear with little
deviation, it would be enough to mesure at 25C and 55C
to get a good aproximation of what's going on.

If serval factors come into play, some with positive, others
with negative sign, I could think that the curves are at least
of third degree (polynomial aproximation), so extrapolation
of only two points could be misleading.
In this case I think that one has to go lower then the
expected operating temperature range of the circuit
to get a better understanding of the first and second derivative.

I think 10C would be sufficient even in this case.

m.c.

-----Original Message-----
From: Ian Fritz [mailto:ijfritz at earthlink.net]
Sent: Montag, 12. Mai 2003 18:49
To: Czech Martin; Sdiy (E-mail)
Subject: Re: [sdiy] Peltier Elements


Hi Martin --

Sounds like you have been making good progress!

Peltier elements are definitely do-able.  Usually you would just mount them 
with the hot side exposed to the room environment.  They *will* heat up 
your room a bit.

The down side of this approach, as I remember, is that the elements aren't 
too efficient and you end up needing to make a big dc supply to run 
them.  The ones I have worked with need 1-2 amps of current to operate.

Other approaches to the cooling problem might be to bring in another, 
non-controlled air stream to increase the cooling rate at the lower 
temperatures or to add some kind of heat exchanger, maybe put some ice in a 
thermos box and bring the air stream across it.

With any cooling aproach remember to take precautions to avoid water 
condensation.

   Ian


At 04:16 AM 5/12/2003, Czech Martin wrote:
>Since my thermo chamber has no active cooling, I'm considering
>peltier elements. They are pretty expensive.
>I think the problem is that I have to maintain a large temperature
>difference, i.e. cool the hot side of the element, otherwise
>it won't cool. This can cause some trouble in the construction
>and thermal isolation.
>
>Any hints/experiences?
>
>
>Martin Czech
>
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