I said:

> Have your DC as ripple free as possible.

> It's claimed that=A0AC on the supply produces thermal cycling which can
> shorten life considerably.
> I'd have thought that AC at a >> frequency than the device's thermal
> time =A0constant should be no great problem, =A0but it's claimed that it
> is. YMMV.

Ken said (offlist message):

> According to at least one major US manufacturer of Peltier devices, rippl=
e is not a problem  - not even at 60Hz  - so any ripple at high (switchmode=
) frequencies is even less likely to be a problem.

Another issue is using on/off switching  for temperature control.
This would produce marked thermal cycling.
Better would (probably) be using  a DC voltage which is varied in
order to try to cause it to just balance cooling against thermal load.
Some mix of PID control is probably  appropriate. Proportional alone
may well suffice.


 Russell



           Russell

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