Gord,

I haven't really sat down and gone through the numbers for heat transfer
yet, but the physical mass would be around 30-50 grams of aluminum. It
would not be exposed to much air flow either. I plan to use a tape style
heating element (http://www.minco.com/products/heaters.aspx) that will be
sandwiched between the two pieces of aluminum.

Thanks,
Bob


"GS" wrote in message
...
Howdy Robert.....Based on my own experience designing a similar
situation I'd want to know what the thermal mass is that you're trying to
heat to get a handle on the stability issue. Based on my own experience,
if you can get away with something simple like a relay to switch your
heater, use that (could be a solid state relay etc). Depending on the
anticipated repairability of this circuit, you could design your own
switching based on everything from bipolar, Power FET to the SCR's or
TRIAC's as others have alluded to.

Because you mentioned stability, the amount of times you'll have to switch
on versus heat loss will be the basic issue assuming you have sufficient
heat input to overwhelm a quickly cooling load. If the heat load is
small and the heater has a lot of output in relation, then you'll be
playing with overshoot a lot more.


Gord