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How to Make a Shake Powered Flashlight with Magnets and Coils

The post discusses a shake powered flashlight circuit using an simple copper coil and a magnet. The idea was requested by Mr. Dennis Bosco Demello

The Design

Electromagnetism was proved way back in 1873  my Maxwell, and later by Faraday, and amazingly the technology still forms the backbone of all the major electrical systems of today's modern world.

As the name suggest electromagnetism is a correlated phenomenon between electricity and magnetism, and appear to be the two sides of the same coin.

In an electrical system, when a magnet is moved close to a conductor, electricity is generated in the conductor due to the mobilization of the electrons in the conductor by the magnetic energy. Conversely when electricity is passed through a conductor, magnetic energy is induced around the same conductor.

In our present shake powered flashlight circuit we take the advantage of this unique electromagnetism phenomenon and implement this to generate electricity from the interaction between conductor and  magnet.

Materials Required


To build this interesting generator circuit we would require the following ordinary and inexpensive materials:

1) A cylindrical magnet



2) An appropriately dimensioned pipe whose internal diameter should be just slightly higher than the outside diameter of the magnet.

3) A few feet of magnet wire or super enamelled copper wire having a thickness of around 30SWG.

4) 4nos of 1N4007 rectifier diodes for making the bridge rectifier, and a 220uF 16V filter cpacitor which could be ideally a super capacitor

5) 1 LED rated at 1 watt, ultra bright, preferably an SMD type

The Circuit Layout






Building Procedure:


The procedure for completing this simple shake-a-gen or a shake powered flashlight circuit is very simple.

Wrap the wire around the pipe as shown in the following figure and secure the wire ends through the end pin holes appropriately drilled on the pipe.

You can wind multiple layers of wires one over the other for acquiring higher current from the unit.

Once the winding is done, slide the magnet inside the pipe, and seal the two ends of the pipe with epoxy glue, preferably do this with a piece of foam stuck at the inner side of the two ends of the pipe.

Let the unit dry until the epoxy has hardened fully.

Next, wire the ends of the coil with a bridge rectifier, a filter capacitor and an LED.

The set up is complete now, and the unit is ready for shaking.

Now it just require holding the pipe within your fingers and giving a quick to and fro shake.

As soon as this is done, the LED could be seen glowing brightly, and the illumination sustained even after the shaking is stopped.

Incorporating a Joule Thief Circuit for Maximum Brightness


The illumination period could be significantly increased by adding a "joule thief" converter with the bridge rectifier, as shown in the following figure, however when this concept is utilized, the number of turns must be reduced and instead more number of parallel turns must be added to the winding, because here the current needs to be relatively higher so that the Joule thief circuit is able to convert it into a sustained amount voltage for the LED



The number of turns in the above joule thief could be with a 20:20 ratio, or other proportions could also be tried for getting a preferred customized amplification.

Coil Specifications for the shake powered flashlight


The coil specifications for the first circuit is not critical, as a rule of thumb make the coil length 3 times the length of the magnet.

The number of turns in the coil determines the voltage level while the thickness decides the current magnitude. 


Preferably, instead of a single thick wire many thin wire strands must be used for acquiring proportionately higher level of current through the system. 

This could be possibly achieved by using a standard 14/36 flexible insulated wire and wrapping a single layer over the pipe, or a couple of layers could also be tried for boosting the voltage along with current.
As suggested earlier the diameter of the magnet must be just slightly lower than the inner diameter of the pipe so that the magnet is able slide effortlessly in response to the shakes, and additionally ensuring a minimum possible margin between the coil and the magnet. This gap decides the efficiency factor of the system, lower gap ensures higher efficiency and vice versa.


Need Help? Please leave a comment, I'll get back soon with a reply!




Comments

  1. Hello,

    Good day. Your website is so much helpful to those who are electronic enthusiasts.

    ReplyDelete
  2. Hi Swagatam,

    Good day. Your site is such an excellent source of information to those who are electronic enthusiasts.
    I'm sorry, I am fresh new here. I don't find your request page. But anyway, I want to request you a circuit, I know it's not common as of this time. An Inverter type airconditioner utilizes a DC compressor motor and a new technology circuitry. Many people are aware this technology is still very costly, not everybody can afford. I am trying to find a way to convert a normal AC compressor to run at lower speed once the temperature setting is achieved, thereby copying the inverter type principle. This is to avoid the on/off operation of the compressor which is eating much power and I am talking about energy saving. I have read somewhere a thermistor might be useful as a temperature sensor for this circuit. With your thousands of knowledge in electronic circuit, I believe you can make one like this.
    I appreciate there is such website like yours.

    Best Regards,
    Paul
    email:casem.apolinario@chiyodacorp.com
    a_casem@yahoo.com

    ReplyDelete
  3. Thanks very much Paul,

    I think it can be accomplished using a VFD technology which I have already covered in this website, however since your suggested application will require an automatic adjustment will need to be a slightly different from the one which I have published.

    I will try to figure out the design and will post it soon for you.

    ReplyDelete
  4. can i include 1.5v rechargable battery to this . if yes how can attach

    ReplyDelete
  5. you can use it, connect it where the LED is supposed to be connected. but if LED is also connected the cell might not get optimally charged.

    ReplyDelete
  6. My intention is to increase the time of glowing

    ReplyDelete
  7. sir, does extending pipe and winding increases efficiency, and that can i include rechargable battery to that
    thank you sir

    ReplyDelete
  8. manjunath, efficiency can be increased by making the gap between magnet and the pipea as minimum as possible, by using multi-fiber wire, and by making the inner surface of the pipe as smooth as possible,

    increasing winding will increase voltage with respect to the shaking speed.

    yes you can include a rechargeable battery in the design

    ReplyDelete
  9. yes that may be possible if all the parameters are appropriately optimized...

    ReplyDelete
  10. sir can 220uf capacitor replaced with 1000uf
    if yes what may be the peformance

    ReplyDelete
  11. Manunath, if your inductor and magnet are able to gnerate more power than 220uF can store then surely you can use 1000uF, otherwise it won't be useful

    ReplyDelete

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