How to Create a Rechargable LED Flashlight





Introduction: How to Create a Rechargable LED Flashlight

Using electromagnets, a small-scale LED flashlight similar to that featured in "Shake It Like a Tic-Tac!" can be produced.

With the setup for the Tic-Tac flashlight, the voltage produced by the magnet alone may not be enough to power up the LED. It is possible that the only reason the LED lit up was due to the rechargable battery not being completely empty in the first place. This theoretical experiment attempts to improve on the circuit based on one of the comments made on "Shake it like a Tic-Tac!"

Image taken from Shake it like a Tic-Tac! page.

Step 1: Parts Needed

1N4148 signal diodes x 2
Magnet 20 mm in Diameter x 1
470u Electrolytics x 2
White LED x 1
Magnet Wire x 300 ft

Ballpen case or some hollow cylindrical tube that can fit the magnets and accommodate the coils of wire

Step 2: Making the Magnet Tube and Wire Coil Tubes

This just calls for building a tube wherein your choice of magnet can move freely within. You can use pretty much anything (even rolled up cardboard would work) for the tube; just make sure that the tubes are stable.

Step 3: Making the Wire Coils

Basically, the magnet in the set-up will pass through two coils in order to increase the generated current. Each coil should be composed of winding the 20mm wire 600 times.

This is perhaps the most boring and time-consuming part, but it is crucial, as this is how the electricity will be generated.

What is important to consider is that the coil should be larger than the diameter of the wire in order for the maximum voltage to be generated.

Step 4: Assembling the Circuit

Mr. Mitchell over here (Jan 27, 2009) had a good idea of improving the circuit, and so here's his diagram to help guide you in assembling the circuit.

Basically, the circuit itself is in series, and it follows this diagram:

The coils actually sit flat against the slide (against the side of the magnet) as shown in the diagram below. You must get the end of the magnet to fully pass though the coil so the voltage will be a maximum. Thats why the slide extends past the coils at the top and bottom of the diagram.

You can solder the circuit together and, there you'll have it.

Step 5: Final Notes

The speed at which the magnet passes through the coils will determine the electricity generated. So, obviously, shake more rapidly, and you'll get light from the LED.

1.6v + 0.6v = 2.2v, and that is the voltage the coil needs to produce.

It is good that there are electrolytics in the circuit, since these will keep the LED illuminated for the time it takes for the magnet to make another pass through the coils.

If the LED still does not light up after following the instructions, be sure to check your connections to see if anything is loose.

Perhaps the LED itself may be busted, so be sure to check that out as well.

Good luck!



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with the coil is there a + and - end or is it determined by the magnet or what? I'm new to this type of thing so any info would be much appreciated

Neither. It puts out AC. Connect it to a bridge rectifier, and you'll get a DC output.

ill try it



You mention making a rotary generator, but I have been unable to find how to make on on my own. Have you had better luck? Thanks.


Very confusing & I'm an electronics technologist !! You crapped all over the origional posting, then took pix from it & made the thing so confusing & useless ... for shame! I could not build anything from your instructions that would do squat !!

i have made a tic tac which uses joule thief which increases output freuency led lasting for more than 4 mins recharging in 5 shakes.

sir i wanna some flying mini project so please send me

What do you mean by "What is important to consider is that the coil should be larger than the diameter of the wire in order for the maximum voltage to be generated." If you mean the total size of the coil, well... naturally the coil is going to be larger than the diameter of the wire. The diameter of the wire is tiny. Do you mean the thickness of the edges of the coil, maybe? Should the wire be wound back over on top of itself?

i agree, because in that case, if you went two times around, you would already be larger than the diameter of the wire. or does this have to do with the spacing of the wire maybe, but then again, that wouldn't make sense.

I, too, do not understand what you meant by that statement. I read it several times. =S I'm assuming the same thing Asbestos is: that the thickness of the coil should be more than the thickness of a single wire (in other words, a short coil with multiple layers instead of a long coil with one layer).