Dynamo Powered LED Without Making a Circuit

Hello guys and girls, this is my first instructable. Do you have a wind-up torch that doesn’t work and a bicycle with bottle dynamo that you want to led-relight, then this instructable will be very easy and no cost to do!

I have a 25 years old city bike that I love to ride. It had a classic system of lights with bottle dynamo, but bulbs burned out on one speedy downhill night ride some years ago. I was going to quickly replace them and don’t know how, but quite a few years went by :) When I found that you can put leds instead of classical bulbs, I wanted those and even there are great instructions on the web how to do this; getting all the parts and making these circuits, was not something I was keen to do. I wanted something simpler, something to use that I already had and no cost. So I found a wind-up torch in my drawer that doesn’t work any more and searched the internet to see is it possible to use it somehow. I got a lot of information about wind-up lamps and how they work, but couldn’t find this exact project (I’m not claiming there isn’t any, I just didn’t find it).

So, what’s the goal? Connect an old bicycle bottle dynamo to a wind-up torch and while pedaling it needs to light up.

Step 1: Things You'll Need

Things you’ll need:

- 1x bicycle (the one that you can mount a bottle dynamo on)

- 1x bottle dynamo (I used the one that was originally on my 25 years old bike)

- 1x wind-up torch with rechargeable battery dead (when it’s switched on it still needs to light up while you are cranking the crank, but doesn’t save power)

- Some very thin electric cable (I used the one that was already on my bike for the old lighting system)

- Some screwdrivers

Optional:

- Soldering iron

Step 2: Dismantling Wind-up Torch

First you need to open up a wind-up torch. I didn’t record this step myself, but I found a video that will lead you through the process and the flashlight in the video is EXACTLY the same as the one I had. If it’s unclear in the video, you don’t have to remove the crank, just unscrew the screws and open the housing.

If you want to mount the lamp with original housing on a bike, you don’t have to dismount it all the way, just the top part off (then the end point is around 2:40 in the video). Even if you do take it apart all the way, it's not a big deal, you can easily put it back together.

After opening a wind-up torch, you could probably replace the dead rechargeable battery and use the lamp as you did before, but if you don’t want to do this, read on.

Step 3: Connecting the Wind-up Torch to a Dynamo

Now you need to connect the torch to a dynamo. This is really simple. Take a piece of cable appropriate length, remove the covering on both sides (a cm or two) and connect one end to the bottom of a dynamo and the other end to one of the connections of the generator in the lamp. To close the circuit, take one small piece of cable, remove the covering on both sides and connect the remaining connection of the generator to some metal part of your bicycle. I advise you to use soldering iron for all these connections (except dynamo connection), but you can also temporary wrap the cable (part without covering) around the stuff.

If you'll be mounting the lamp with original housing on the bike, you just have to make a hole in the housing for the cables, close the housing, mount it and you are ready to ride.

I'm not sure if the generator in the torch would take some power if you connect it this way. You can pull it out anyway and use it for some future project. I accidentally pulled out one red wire from the generator, so I connected that red wire directly to the cable and that's the way I tested it. Take a look at the next step image for this!

Step 4: Test Build and First Ride

As you can see, it works. It's not a great deal of light, but you will be visible.