Introduction: Body Heat Powered Flashlight

Picture of Body Heat Powered Flashlight

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Astrasekar (author)2017-08-11

need help immediately, steps have been deleted from the site, we need help with the project so please look into this and reply asap

ndawood777 (author)2017-06-12

So if i actually make this will it work?

Reid G (author)2017-02-27

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.

MITinventorbot (author)Reid G2017-02-28

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!

tomatoskins (author)2015-03-03

This is a really cool concept! So much can be done with this information! Thanks for sharing!

Thank you!

pleaseplease!! i need help! does it ACTUALLY WORK i need it and i CAN NOT WASTE TIME

EduardoM189 (author)EduardoM1892016-12-05

does it work


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.

madeline21 (author)2016-12-03

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?

MITinventorbot (author)2016-09-29


PriyanshuS11 (author)2016-09-03

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
Please reply fast... I need to know urgently because I am creating a phone charger out of this

PriyanshuS11 (author)2016-09-03

Hey, can you please tell me that the output is dc or ac and also what is output voltage
Please reply fast... I need to know urgently because I am creating a phone charger out of this

amackinnon2 (author)2015-07-25

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

ChickBang (author)amackinnon22016-08-24

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

Uproar01. (author)amackinnon22015-09-19

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.

sebeTNT (author)Uproar01.2016-05-21

they are selling thier website so there is nothing to buy

Alligatorrr (author)2016-08-21

Whats the independent and dependent variable in this experiment?

TejasB4 (author)2016-08-07

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...
Please help me!!!! I have to submit it tomorrow! Please!
Thank you :)

DennisM131 (author)2016-08-02

where do i solder the usb charging circuit?

SmartK3 (author)2016-07-16

hello !

i cannot boost the voltage from 0.35 v .

can u pls help me out

Jac_thepro (author)2016-07-10

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.

aconfusedfish (author)2016-04-17

what is the use of the toroid?

GeromeC2 (author)2016-03-10

Can we use plastic bottle instead of ftc tube?

AshwasM (author)2015-12-05

What is the toroid ? How it is made ? And what is that donote shaped susbtance ?

atia_1302 (author)2015-10-18

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

please and thank you :)

rana001 (author)2015-07-21

hi your project is awesome but i do have some doubts regarding it

can we use any medium size peltiers or some specific ones

trainfest (author)2015-04-24

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.

MITinventorbot (author)trainfest2015-04-26

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!

trainfest (author)MITinventorbot2015-05-14

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 :)

nate71173 (author)2015-03-03

Great, brilliant concept! Does it work? I noticed none of the pics show the bulb energized.

MITinventorbot (author)nate711732015-03-03

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.

I posted a picture of the circuit with an LED in it when it is illuminated.

Arx (author)MITinventorbot2015-03-17

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.

MITinventorbot (author)Arx2015-03-17

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.

Geeve George (author)2015-03-04

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

Arx (author)Geeve George2015-03-17

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 "produces just the right amount of voltage" 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.

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.

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

MITinventorbot (author)Arx2015-03-17

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.

Arx (author)MITinventorbot2015-03-17

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.

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.

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.

That's assuming that it's properly designed. If it's badly designed it might just blow its mosfets or something.

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.

Arx (author)Arx2015-03-17

oops, I mean the charger has an expected input _voltage_

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!

Thanks for the ping.
I will be trying with four , all TEC'S.
Thanks if I have any queries I will be informing you after my 10th Grade School Exams.
( )

antoniraj (author)2015-03-13

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 :

MITinventorbot (author)antoniraj2015-03-13

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.

antoniraj (author)MITinventorbot2015-03-13

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

MITinventorbot (author)antoniraj2015-03-14

Congrats to you too! Good luck...

Coldfire1215 (author)2015-03-11

Very creative! A definite necessity in an emergency situation! Well done!

Thank you!

liam.plybon.3 (author)2015-03-06

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.

About This Instructable




Bio: I am a passionate inventor who is always thinking of new ideas and making them a reality. I do not attend MIT, that is just ... More »
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