Picture of Solar powered vintage rear bycicle light
I have an old bycicle and I really like its classical design.

When I bought it  [from a weird old man..] it was equipped with front and rear bulb lights, powered by a dynamo.
As you maybe already know, this is not the best solution to light your way home at night: dynamo and inertia are enemies and the dim light of bulb lamps turns off as you stop at a crossroad.

After some months of sweat and darkness, I wanted to switch to a more efficient solution but I didn't like how modern LED torchs looked on my bike.

So I decided to create my own classical looking light.. with future inside.

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Step 1: Stuff and Tools

Picture of Stuff and Tools
you need just few materials:
- original rear light (free)
- chinese solar torch key-ring (2,5€)
- small  toggle switch (1€)
- red LEDs stripe, I've taken it from another bike light (1€)

and tools:
- scissors
- screwdriver
- tweezers
- hot glue gun
- tin wire
- soldering iron
- desoldering pump (optional)
- multister (optional)
- dremel (optional)

Step 2: Modify the old light

Picture of Modify the old light
First of all you have to open the old light and remove bulb and its metallic contacts and support.
We need only the plastic case, the red reflector and the clear red cap.
Widen the side hole, where the wire from the dynamo used to be, until the toggle switch fits inside it.
If needed enlarge also the upper hole where the LEDs will be placed.

Step 3: Open the solar torch

Picture of Open the solar torch
Open the torch and pick out the electronic stuff.

You should find a circuit made of:
- a mini solar panel
- a rechargeable battery
- a switch
- LEDs
- a diode
- a resistor

this circuit is really simple but maybe you want to take some pictures of it before desoldering anything.
why not 2 leds in series? It's more efficient with one current you light up 2 leds
olmon2 years ago
Really excellent and practical instructible. I have been planning on installing solar lighting on my Rhoades car & plan to use a solar spot-lite kit that just happens to have 4 lites in the kit so all I have to do is mount them and make red lens for the rear lites. The solar charger already has an on/off switch so I got lucky there.
jeffeb33 years ago
Maybe something is just missing from the schematic, but typically, you would either wire the LED's in series, or give each one their own resistor. Unless they are perfectly matched, you will get dim ones and bright ones with them in parallel with only one resistor. It's possible there is some resistance built into the LEDs. Maybe that's why you aren't having problems.
eriol (author)  jeffeb33 years ago
you are perfectly right, this is not the best solution.
Anyhow in the schematic is shown the circuit as it was in the original torch and as it is in the final result. Breadboarding the project showed no problem with the wiring of the recycled red LEDs, so I've used them this way. As the sayng goes "chinese engineers knows better!", right? ;D
Caledo3 years ago
Great !!!