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
Pliers
Sandpaper

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!