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DIY led rechargeable torch

Category: Electronics & Technics

DIY led rechargeable torch

LED rechargeable torch

difficultyDifficulty: ★★★☆☆

timeTime: About 2 hours

ScrapFrom scrap: ████░░░░░░ 40%


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.


  • 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

  • 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.
    DIY led rechargeable torch

  • 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 .
    DIY led rechargeable torch

    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
    DIY led rechargeable torch

  • 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
    DIY led rechargeable torch

    DIY led rechargeable torch

  • Step 6

    Measuring the voltage on the capacitor
    DIY led rechargeable torch

  • Step 7

    Make a cardboard case for flashlight and strenghten it with tape
    DIY led rechargeable torch

  • Step 8

    I took the lens out of a device for viewing negatives or something like that
    DIY led rechargeable torch

    DIY led rechargeable torch

  • Step 9

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

    Author: ChemistR


Demonstrating of Faraday's law of electromagnetic induction

ResultsResults 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
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