This is a hack for turning a fairly useless, dim, shake to recharge torch, into a torch which is bright, long lasting and can still be recharged but not just by shaking. This type of torch usually charges via shaking, and a magnet slides between two coils and charges a tiny three cell battery. The battery is small so it charges quickly while shaking, but needs almost continue shaking to maintain brightness, this is a bit of a pain.
What i did is i took the torch apart and rewired it with a bigger battery for both more brightness and more storage, the three LED's i wired all in parallel and a re-did the circuit board as it didn't have a diode between the coils and the battery, which meant some power was going back into the coils.
Because of the bigger battery it would take longer to charge so i made an adaption so it can be charges by either, shaking, like previously, the movement of a tree branch in the wind, or a fluttering wind generator. These all work by pulling the magnet up and down via a string, so almost any movement could be harness, like the turbulent flow of a stream or flapping of a flag.
I found the best way to charge this, is to clip the string to one corner of a t-shirt on your washing line when you are camping, the flapping of your clothing creates plenty of up and down movement to charge your torch.
Step 1: Tools and Materials Required.
- Soldering Iron and Solder
- Craft Knife
- hot glue gun
- One shake to recharge torch
- A old cordless phone battery
- Small piece of strip board
- some nylon string
- Balsa sheet
- tooth picks
Step 2: Taking the Old Torch Apart
Taking apart the old torch was easy. Un-screw then lens cap and all the insides out, do not amage anything or throw anyhing away as we use most of it.
Step 3: Removing Electronics
Start by removing the coils from the main circuit board, be careful not to damage theses as they are hard to fix. after that, un-solder all the components from the board. There should be two bridge rectifiers which convert the AC current from the coils to DC to charge the batteries, a switch, three diodes (these were used so there could be one LED on or all three), three LED's and the battery. You can now get rid of the old battery and the circuit board as we wont need them any more.
The old circuit didnt have a diode between the coils and the battery, so when you weren't shacking, the battery power would drain back though the coils, instead of staying in the battery. I used one of the three diodes to prevent this and greatly improving the torch.
Step 4: New Electronics
The circuit couldn't really get any simpler. Cut out a rectangle of the strip board 9 holes by 12 strips, or however big your previous circuit board was, this is so they fit into the same place. now solder on your components using the circuit diagram as a guide, because it is a simple circuit there is no need for a strip board diagram. remember to break the strips where it is needed. The switch doesn't go on the circuit board as it will be sitting on-top of the battery. The battery is out of a cordless phone and is 4.8 volts, compared to the previous smaller battery which was only 3.6 volts. The flat cells fit tightly on-top of the circuit board and deform, the silver reflector a bit, but everything still fits. when you solder on the LED's and battery, make sure you get everything the right way round and that all the LED's light up when the switch is turned on.
Step 5: Assembling
Once you have tested the circuit slot the LED's into the holder then the battery and circuit board behind it. because the new battery makes the torch longer, a bit has to be cut off the end of the magnet tube so that the electronics can fit in. because we arn't putting the rubber stop back in the end, the magnet still moved enough though the pipe to generate power, it will just have a knock at the end.
In the end of the case drill a 1mm hole and thread a piece of nylon string through and tie it around the magnet from the end stop. this will attach the nylon string to the large magnet, but allow it to be removed as well. now slide all the electronics back into the case, making sure the switch is the right way round and screw on the lens cap to prevent anything falling out.
Now test the switch and make sure everything works. tilt the torch so the small magnet with the nylon on it attaches to the large magnet and test that you can pull the magnet up and down to produce power!!!
Now you can use your improved rechargeable torch and charge it via tree, flag or shaking!!!
Step 6: Wing Power
This wing allows you to charge the torch without a tree of a flag, It oscillates in the wind and pulls the magnetic up and down as it zig zags. It is made from a 3mm thick piece of balsa wood, sanded into a rough aerofoil, it doesn't need to be accurate. Tie the nylon from the magnet to the bottom, about a third back from the front of the wing then the same at the top but to the roof or a branch, just something to suspend the wing. with tooth picks and a small piece of flat balsa make a tail that keeps the wing into the wind, otherwise it spins round lots instead of zig zaging. Paint it up so it looks good and hang it up in the wind. as the wing flips from side to side it should pull the magnet up and down rapidly which creates power!! The photos explain this part well
Step 7: Finished!
now you have a good rechargeable torch! tie it up to a tree or your washing and watch it charge ready for when you need it! Here is a short video of it in action! Charging from the wing, a tree branch and a flag. The flag was very good as its simple and lots of movement is created in light winds with the tail flicking around. This is great for clipping to the corner of your washing while you are camping and the wind flapping your clothing does the rest.