Humans are a living energy source. We produce body heat, we walk, and our blood flows throughout our body. All of these energy sources from our body can be used to generate electricity. So why have we not taken advantage of those sources, and used them, especially for people do not have access to electricity? So why waste readily available energy that is available to every human? This solution converts body heat into electricity, and makes electricity available to anyone.
Now, this was quite the challenge, because your body generates a small amount of heat, and is a small temperature differential compared to air. Each thermo-electric generator, or peltier, only generates 0.1 volts when placed against your skin. In order to increase that voltage, I did two things. First, I wired three peltiers in a series circuit, so that together they generate 0.3 volts. From there, I used a joule thief circuit to boost up the voltage to power a light, as a joule thief can take in voltages down to 0.3 volts! If you were using this for a body heat powered USB charger, you would just use a voltage step up module to step up the voltage to 5 volts.
Step 1: Materials
The materials you will need for this project are:
- 3 small peltiers
- 2 different gauges of magnet wire
- 2 volt -3 volt light bulb, I highly recommend an LED, because when I used a regular light bulb, it barely lit up, (that is why you do not see the bulb lit up very much in the pictures), but when I used an LED, it was as bright as can be!
- Ferrite core
- NPN transistor, any kind
- 4.7 ohm resistor (can be any type, that is just what I used)
- T12 FTC tubing (it goes over fluorescent lights)
- Black paint
- Aluminum foil
- Scotch tape
Step 2: Preparing the Tubing
Measure four inches of the tubing and cut it. Mark out the places where the peltiers will be with a sharpie, and cut the squares out with scissors and an X-Acto knife.
Step 3: Painting the Tubing
Next, paint the outside of the tubing black. Let it dry for at least two hours, and paint another coat if needed.
Step 4: Making the Cardboard Disk
Mark a small circle the same diameter as the tubing. Cut the circle out, and then cut two small notches at each side. Glue this in the tubing on the end that is closest to the three square holes.
Step 5: Wiring and Soldering the Peltiers in Series
Take your three peltiers and cut the middle one's leads short. Make sure that all of them are on the same side (for mine, the hot side was the one with the writing on it). Take the other two and cut one lead short, one long. Also, make sure there is only one positive and one negative. Solder these together in series.
Step 6: Taping the Petiers
Now, put duct tape on each end of each peltier, and tape each one above it's hole.
Step 7: Threading the Peltier Wires
Next, solder extra wire onto the peltiers negative and positive joints, if needed. Poke two holes in the side of the tubing, and thread the wires through the tubing and through the notches in the cardboard.
Step 8: The Toroid
Twist your two lengths of magnet wire together at the end. Wrap the wire around the toroid until it is covered in wire. It does not matter which direction you wrap it in. Once done, scrape off the coating at the end of the wire on each wire, either with a knife or sandpaper.
Step 9: Wiring the Joule Thief Circuit on a Breadboard
In this step, we will be wiring the joule thief circuit, or the circuit that steps up the voltage from the peltiers to light the LED. First, put your transistor somewhere on the breadboard with the flat side facing you. Be very careful with it, as the legs can break off very easily. Plug one side of the resistor into the middle lead of the transistor. Plug the other side in about ten columns over. Take your LED and determine which side is positive and which side is negative. The negative side is usually shorter. Put it into the left and right transistor legs with the negative side on the left side of the transistor. Take your toroid, and separate the wires. Plug one of the red wires into the right lead of the transistor, and the other green wire that it was coiled with and plug it into the right side of the resistor. Take the remaining red wire, and plug it in a few columns down to the right of the resistor,and plug the last green wire in right below it.
To test the circuit, take two spare jumper wires, and plug one into the left (negative) side of the resistor, and the other one into the red and green wires that are a few columns down from the resistor. Attach the wire plugged into the LED to the negative side of a 1.5 volt battery, (not enough to power a 2 volt LED) and attach the other jumper wire to the positive side of the battery. The LED should then light up.
Step 10: Soldering the Circuit
First, solder a red and green wire together from each side of the toroid. Take one loose toroid wire and solder it to one side of the resistor. Bend back the middle lead of the transistor. Solder that middle lead to the other side of the resistor. Take two jumper wires and solder them to the side leads of the transistor. Now, solder the other loose wire from the toroid to the right side of the transistor. Lastly, solder the LED to the two loose jumper wires, with the negative side to the right of the transistor.
Step 11: Soldering the Peltiers and Joule Thief Circuit Together
Take the negative side from the peltiers, and solder it to the right side of the transistor. Take the positive side and solder it to the two toroid wires that are wrapped together.
Step 12: The Final Details
Finally, almost done! Stick duct tape in between the peltiers. Use aluminum foil and cover completely over all of the peltiers, on top of the duct tape. Hot glue the LED to the end cap, in the small hole. If your end cap does not have a hole, then cut a small one, just enough for the light bulb to get through. Cut a round disk of aluminum foil with a hole in it, and glue it over the light bulb. Congratulations! You are done!
Step 13: Looking Back...
Looking back, I see several improvements I could have made to this project. If you would like to use some of these ideas in your flashlight, it will make it a lot better and more efficient.
- Body heat charges batteries, which in turn power the light
- Make the tubing bigger, but the peltiers closer together
- Add a USB charger to it to charge your devices
- Generate more voltage with peltiers, maybe by cooling the other side with ice