DIY led rechargeable torch

Category: Electronics & Technics

LED rechargeable torch

Difficulty: ★★★☆☆

time

Time: About 2 hours

Scrap

From scrap: ████░░░░░░ 40%

Preamble

I'm going to present you an interesting led flashlight that works on Faraday's law of electromagnetic induction. Just shake it - and it will recharge.

Materials

LED, one or more
2 diodes
2 electrolytic capacitor of 470 uF and voltage of 16 volts
Copper wire (unwound from a transformer)
A powerful cylindrical magnet
The tube with an internal diameter slightly larger than the magnet and caps at the edges
If you haven's such tube, you need: paper, matches and glue
Clear Lens
Foil

Tools

Scissors
Soldering iron
Duct tape
Glue

Faraday's torch

Physics

If you push a magnet in a coil, induction current will occur. When you remove the magnet from coil, induction current will accure too, but the other direction. The strength of the current depends on the speed of movement of the magnet in the coil.

Step 1

First you need a tube. If you can not find a suitable tube to the magnet, it can be very easy to do. To do this, spread a sheet of paper with glue and twist it into a tube with an internal diameter slightly larger than the magnet and wait until the glue dries.
Cover inside surface of tube with tape before qlueing. Tape will reduce a friction for magnet

Step 2

To make the caps, near the end of the tube stuck matches crosswise and glue small circles of paper in several layers to them. In the next photo you can see the contours of paper matches through the paper .

Don't forget to put magnet inside, before making caps!

Step 3

The tube is mentally divided into parts according to the length of the magnet, I've got three parts

Step 4

Now the most difficult and boring part. Each sector of the tube need to be tightly wrapped by copper wire turn to turn in 3-4 layers

Step 5

That original scheme, connect all the elements according to it

Step 6

Measuring the voltage on the capacitor

Step 7

Make a cardboard case for flashlight and strenghten it with tape

Step 8

I took the lens out of a device for viewing negatives or something like that

Step 9

The reflector lens is made of foil. The final version of my Faraday's led rechargeable torch

Author: ChemistR

Video

Demonstrating of Faraday's law of electromagnetic induction

Results and tips

Later I remake the torch in a stand-alone battery charger for smartphone
Instead of electrolytic capacitors is better to use electric double layer capacitors