# Powering an LED with a Thermoelectric Generator

## Can a small Thermoelectric Generator feasibly power an LED?

I want to make a small LED circuit that consists of a coin cell, an LED, and some sort of touch-sensitive switch. The entire circuit needs to be very small (~3cm³), and there must be no moving parts. The circuit is for a jewelry piece so it doesn't need to act within finely tuned boundaries at all times, all I want is for the LED to glow visibly when the circuit is held.

I've never used TEGs before, but after reading a question from earlier this year I would like to know if a small TEG could be used, essentially to act as both switch and power source. I tried figuring it out but I am still struggling to understand the relevant information on this page and the related datasheets.

I would like to use one in the 10mm - 20mm range if possible, using this as an example. My understanding is that since they work on temperature differences, if a temperature gradient of 68deg / 27deg produces 8.8V, then a typical human/room temperature gradient of 37deg / 27deg would produce around 2.2V, enough to power your typical 1.5V LED.

Am I correct in this assumption?

• LEDs need a specific current, not just voltage. How much current can your TEG generate? And I would assume that you won't get it up to body temp unless it is in somebody's armpit. Dec 12, 2017 at 2:44
• Well I sure feel silly, I would mention that I'm self-taught, but 'taught' would be an overstatement... If current follows the same guesswork I used for voltage, then it would provide 0.2A, which is more than the 0.05A required for, say, this LED. However I no longer have any confidence in my ignorance-based theories. Dec 12, 2017 at 2:55
• While a small (say 2x2 inch) TEG attached to a wood stove can probably power LEDs quite nicely, I'm going to say that an even smaller one, powered by hand heat and air cooling, almost certainly can not. Sorry.
– user16324
Dec 12, 2017 at 10:36