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Old 09-22-2014, 09:18 AM
thx1138 thx1138 is offline
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Join Date: Jan 2012
Posts: 371
Seebeck Effect

The Seebeck Effect is what makes thermocouples work. My first experience with one was the thermocouple on a gas water heater. The end of the thermocouple is positioned in the flame of the pilot light. The main gas valve to the heating burner detects the presence or absence of the electricity from the thermocouple. If the voltage from the thermocouple is present at the valve controller it allows the feed to the main burner to open and thus heat the water. If the voltage is not present the controller keeps the main supply to the burner turned off since there is no pilot light to light it. When the thermocouple fails the main burner will not light because, although there is a pilot light flame, the controller doesn't sense it. That's what happened to me and what got me to look into it.

Thermocouples can be made from any two dissimilar conductors. The water heater thermocouple is made from copper and iron. The key is the separation between the ends where one end is hot and the other is cool. That heat gradient between the ends is what sets up the electric potential. They can be engineered for just about any particular heat range needed depending on the materials used.

I haven't seen any documentation on carbon being used in the Hendershot device. But I guess we could consider the carbon in the metal coffee can to be the source.

I don't see it working that way though because as soon as there is a short in the capacitor part of the capcoil it is no longer a capacitor and therefore no longer a tank circuit. So it would just be a shorted coil.

What would be nice is to find a thermocouple that would work between 70F and 120F. I could then harness the power of the gradient between the attic of my house and the interior. I've never seen anything that would work on that small of a gradient though.
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