> Peter L. Peres wrote: > >> >> I wonder if the thermocouple stack used in some gas powered water heaters >> could be used for this. According to Bill & Pookie he (they?) has (have) a >> water heater that has the thermostat powered by such a device. This >> suggests it makes at least a volt (am I right ?). Thus such a device could >> be bought as a spare part and a dc/dc converter powered from it. Has >> anyone got one of those things as a spare and is willing to test the open >> circuit voltage and Rdc on it ? I have looked them up and they are pricey >> to buy, especially if they do not work as hoped. >> >> Peter > > You can buy all sorts of peltier devices commercially, in whatever shape you > want. Is this what you're referring to? No need to find a special > water-heater part. > http://tedist.com/ The part I was referring to is specifically designed to operate in direct contact with an extremely hot gas flame. What I had in mind was something like this: but with higher output voltage (up to a volt - they exist but they are rare). Here are some people who appear to be doing what I proposed (but for a different purpose): Basically you have a few thermocouples in series which make, say, 200mV (four thermocouples in series at 1200C tip temperature make about that much), and a low loss low power dc/dc converter that turns this into 3V or 5V to run a microcontroller with. Maybe Bill can say what make his furnace is. Peter -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist