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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
  • Cardboard
  • 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
<p>So does it work or not. I'm not making it if it doesn't. You have a comment from a few months ago that says it doesn't actually work but another from a couple years ago that says it does.</p>
It does not work, however, the concept works. If you want to improve on the circuit schematic, I am sure you can get it to work. Good luck!
<p>This is a really cool concept! So much can be done with this information! Thanks for sharing! </p>
<p>Thank you!</p>
<p>pleaseplease!! i need help! does it ACTUALLY WORK i need it and i CAN NOT WASTE TIME</p>
<p>does it work</p><p>???</p>
<p>In theory, yes. In actuality, no. I put the design up here with the hope that somebody else would be able to make it work. I am sorry for any inconvenience. </p>
<p>hey, i did this project and use all of the same supplies but it is not working. do you have any reasons as to why it might not work?</p>
Hey, can you please tell me that the output is dc or ac and also what is output voltage I want to use your design and in place of led I will place Pololu 5V Step-Up Voltage Regulator U1V11F5 will it work please help me <br>Please reply fast... I need to know urgently because I am creating a phone charger out of this
Hey, can you please tell me that the output is dc or ac and also what is output voltage <br>Please reply fast... I need to know urgently because I am creating a phone charger out of this
<p>So, I will try to be nice but did you when you did your school project give the correct credit to a girl who did this many years ago? I certainly hope so, In most schools today this would be a failing mark if you did not. Good work, nice instruction http://www.extremetech.com/extreme/160003-15-year-old-girl-invents-flashlight-powered-by-the-heat-of-your-hand</p>
<p>I'll try to be nice, but this girl invented nothing, this isn't plagerism, just like plugging in a light bulb into an electrical outlet doesn't get you a plagerism citation just because someone did it before you</p>
<p>I'll try to be nice, if you actually did your research you'll find that girl invented nothing new at all, I should also mention a site called thermalforce has been selling similar flashlights almost a decade, how I know this? I too had the very same idea.</p>
<p>they are selling thier website so there is nothing to buy</p>
Whats the independent and dependent variable in this experiment?
Hey....I tried to make it too. But, my flashlight is not working! I've used the same things you have but the TEC12706 instead of the one you have...<br>Please help me!!!! I have to submit it tomorrow! Please! <br>Thank you :)
where do i solder the usb charging circuit?
<p>hello !</p><p>i cannot boost the voltage from 0.35 v .</p><p>can u pls help me out</p>
Is it ok if I don't use the tubing
yes, just as long as you use something similar, such as a paper towel roll.
<p>what is the use of the toroid?</p>
Can we use plastic bottle instead of ftc tube?
What is the toroid ? How it is made ? And what is that donote shaped susbtance ?
<p>how can you add a usb charger. p;ease reply fast because im going to do this in few days. and plz tell me if this works</p><p>please and thank you :)</p>
<p>hi your project is awesome but i do have some doubts regarding it</p><p>can we use any medium size peltiers or some specific ones</p>
Hey, so a couple of my friends and I decided to try this for our science exhibition in school(is that okay with you?) and for uses we were thinking about writing how it can be used for hiking and trekking. I would like to hear your opinion about it.
<p>That's great! I would not mind that at all. In your project though, you might want to make it more efficient. In mine, for example, I used peltier modules instead of Thermo electric generators, just because I did not have access to a thermo electric generator. You also may want to experiment with the circuit to see if you can get the joule thief input voltage any lower, just in case it is not as reliable. If not, you can always just add another thermo electric generator to the circuit. Good luck with your project!</p>
<p>Thank you for letting us use your idea! We will definitely keep your opinion in mind. Although we would like to ask if you could provide us with a schematic diagram(if its not too much of a problem). Once again, thank you for lending us your idea :)</p>
Great, brilliant concept! Does it work? I noticed none of the pics show the bulb energized.
<p>Thank you! Yes, it does work, the light bulb I used was from an old flashlight, and I did not realize that it was almost dead at the time. After all of my experiments, the light bulb gave off hardly any light, and I had no light bulb to replace it. In the pictures, it does give of a very tiny amount of light, but you cannot see it. </p>
<p>I posted a picture of the circuit with an LED in it when it is illuminated. </p>
<p>It's not a problem with the light bulb. The problem is that your circuit won't produce nearly enough power to properly light an incandescent bulb. An LED would work much better.</p>
<p>It is a problem with the light bulb, because after it gave off barely enough light, I took it out of the circuit and tested it. It still gave off the same amount of light. Plus, that bulb was from a five year old flashlight. You are correct though, in stating that an LED works much better and gives off much more light, that is why in the materials list I said that an LED was highly recommended.</p>
<p>How much volts can be produced by three peltiers with the help of the joule thief? Also for the USB Charger could you share the Voltage , Amps required . How many peltiers do you think would be required to charge a phone via usb? Thanks! Kudos amazing build :D</p>
<p>The joule thief is an unregulated boost circuit, so it's not really ideal for powering most devices. It works for an LED, because the leds have a fairly huge range between enough-to-turn-on, and enough-to-cause-damage. MITinventorbot's comment of &quot;produces just the right amount of voltage&quot; isn't really accurate, it's true in the LED case, because the LED starts conducting current as soon as you reach its forward voltage, and a typical joule thief doesn't store enough energy in its coil to over-current the LED.</p><p>In the case of most other circuits, they'll either be regulated, in which case they will waste a good percentage of their energy to heat loss, or they aren't regulated, and will potentially give the device too much voltage. </p><p>In most cases the lack of power available will save you, but it's still not going to work well, or reliably, with any device which expects a stable power source. Your average USB charger is between .5 and 1A, so you're going to need several watts of power to run it, where the average led will light up around 0.001W and be very bright by about .025W</p>
<p>What I meant in just the right amount of voltage is that the high spikes in voltage normally are short enough and high enough to power the device attached to it, although it does work better with an LED, as it has a larger range of voltage input.</p>
<p>The spikes will be clamped by the LED. If you were to be looking at them on a scope, they will be cut off at the led's forward voltage.</p><p>The reason it works well for LEDs is because they have a wide range of input _current_ with a fairly constant voltage, and because they can operate down to almost no current without problems(just dimmer). With something like a charger, it probably has an expected input current which is not expected to change drastically under load.</p><p>What would likely happen is that the joule thief would charge the charger's input caps, until the voltage is high enough for it to start, then it would start charging the battery, which will draw too much current and the voltage in the input caps would fall, and the charger would shut off, until the caps charge up again, and would repeat indefinitely.</p><p>That's assuming that it's properly designed. If it's badly designed it might just blow its mosfets or something.</p><p>If you do want to do something like this with a more complex load you would probably want to use a dedicated boost regulator chip with low voltage cutoff. (or buck-boost or buck, depending on your input voltage range) That way it'll just shut off cleanly when there's insufficient power available, and will not overvoltage the load when it's too light.</p>
<p>oops, I mean the charger has an expected input _voltage_ </p>
<p>Thank you! Technically, you cannot determine the exact amount of voltage generated by the joule thief, but it normally produces just the right amount of voltage for the device attached to it. I also did some experimenting with the USB charger, and found that in order to generate enough electricity, you would need ice, or something cold to cool the other side of the peltier. In addition to that, I used a USB step up module to regulate the voltage going to the USB port. However, this concept only worked with the ice cooling the other side, so it seemed like an inconvenience to me to be carrying an ice pack around. I did not, though experiment with more than three peltiers, as my original idea was it to be a wristband, and you cannot really put more than three on your wrist. If you would like to try more than three, I would be interested to see what happens. Thank you so much!</p>
Thanks for the ping.<br>Yes,<br>I will be trying with four , all TEC'S.<br>Thanks if I have any queries I will be informing you after my 10th Grade School Exams.<br>Regards,<br>Geeve<br>( www.geevegeorge.co.vu )<br>
<p>good idea... but you have entered this instructable in four contests (Make Energy, Small space, Explore science and Apocalypse Preparedness) which is not allowed as per contest rules. Please go through the contest FAQ here :</p><p>https://www.instructables.com/community/Contest-FAQ-Frequently-Asked-Questions/ </p>
<p>Thank you for bringing this to my attention. I had not realized before that you were not allowed to enter your instructable in more than three contests, so at your request, I have un-entered my instructable from the Explore Science Contest and the Small Spaces Contest. Once again, thank you for bringing this to my attention, as I try my best to play by all of the rules.</p>
you are welcome. As you are new you may not be aware of the contest rules. Congratulations for being a finalist in Make Energy contest
<p>Congrats to you too! Good luck...</p>
<p>Very creative! A definite necessity in an emergency situation! Well done!</p>
<p>Thank you!</p>
Perhaps if you opened the ends of the tube to airflow, you could enhance the temperature differential. I don't know much about these kinds of things, but from what I do know it makes sense.
<p>Good idea, the end cap I put on the end of the tube had a hole in it, so I do not think it made much of a difference... </p>
<p>NPN what do u use sir? can i use 2n3904?</p>
<p>You can use any type of NPN transistor, including the 2N3904.</p>

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