Few electronics principles can inspire a gasp of amazement. Generally if you want to please a crowd, you have to push some serious voltage and get some arcs going. Another experiment, however, never fails to impress: the Seebeck Effect. For those who need a reminder, the Seebeck Effect allows you to convert temperature differences directly to electricity without any mechanical bits in-between.
Sean Hodgins, a student at McMaster University in Hamilton Ontario, felt like the impact that the Seebeck effect can have on people deserved making a cool way to show it off. He decided to make a ring that would harvest energy from his body heat to light an LED. This wasn't going to be a simple task for him, his major is automotive and vehicle technology, not electrical engineering. He had never designed a PCB before and had a lot of research to do.
He started out by just measuring what kind of voltage he could create from his hand through a Peltier unit. He was able to pull roughly 0.3V in an air-conditioned room. This gave him somewhere to start as he knew he would need to get his voltage up in order to run an LED. After some searching and a bit of trial and error with a Lipower boost converter, he ended up finding a Linear Technology 3108 Ultralow Voltage Step-up converter and power Manager. This looked like it would be perfect, but represented even more new experiences for Sean, as it was a surface mount item.
Some patience and a datasheet allowed him to work up a functional prototype circuit. From that point onward, all that was left was to clean things up and build the ring. His final PCB design ended up being roughly 33x13mm, small enough to fit on a large ring. After a little thought, he concluded it would be a large ring indeed. He decided to make something that fit on two fingers instead of one, allowing for even more surface for heat differences.
As you can see, he managed to pull the entire package together successfully. It isn't the brightest LED, or the most stylish ring, but it is a pretty cool project that will surely amuse anyone he shows. He has also decided to further improve the system by altering the circuit to allow the LED to flash once it has enough power to fully light. This should make for a slightly more impressive display.
— Caleb Kraft, Chief Community Editor, EE Times