> > > PWM will be fine..
> > >
> >=20
> > Out of curiosity, why do you say that? It has been said that this leads=
 to
> > inefficiency and greater heat dissipation in the element when there's "=
that
> > much" line ripple.
>=20
> Because you said efficiency doesn't matter.
>=20
> Yes, at say 50% PWM into the Peltier will produce more heat and be less
> efficient then if you ran it at 6V, but who cares? Run it at 7V and be
> done with it.
>=20
> Or go with the solution I mentioned, your circuit will contain just one
> additional element, very simple.

Over the years I have used a lot of Peltiers and you can do whatever you
want to them if you can accept the consequences.

So if it is a low-performance situation, or if you have tons of cooling
available on the hot side, you can use bang-bang thermostats.=20

If you want to operate with a large temperature differential or get good
efficiency, you need smooth (ripple <10 percent) variable DC.

Forget raw PWM, if you are going that far then add an inductor and
capacitor and make it DC.

Also if you intend to do only proportional control, don't expect it to
be very good because the Peltier has a voltage drop that is related to
the differential temperature. So do full PID or at least PI. And monitor
current rather than duty cycle if you want linear control.

Cheerful regards,

Bob

--=20
http://www.fastmail.fm - Faster than the air-speed velocity of an
                          unladen european swallow

--=20
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