Bike Helmet Lights

A low profile neat way of adding lights to your bike helmet without damaging the helmet or permanently attaching anything to it. The mod uses a universal phone charger as a compact power supply that uses a single AA battery. 


You will need:

Helmet
 2 x 10mm 0.5W white LEDs
2 x 5mm high brightness red LEDs
3 x resistors (about  12 to 20Ohm)
Solid core wire
Heat shrink: various small sizes
1 x 5g pack of sugru
Polymorph
Switch
1AA type universal phone charger
Small piece of thin ply wood or tough plastic.
Total probably comes in under £10.

Tools:
Basic woodwork
Basic soldering / electronics tools

Step 1 The Circuit

Power: I chose to use a AA powered phone charger, it is a small and neat case which conveniently boosts the voltage of the AA cell (1.5V) to about 5V which is suitable for powering the LEDs. I have seen the phone chargers for between  £3 and £5 in several shops (Tesco and Maplin).

Phone charger provides roughly 5v but when the LEDs drew current I found the voltage dropped a bit. To get the correct currents through the LEDs three 12 Ohm resistors worked well for me. Resistor values between 12 and 20 Ohm are likely to be suitable if you are using 0.5W white LEDs, but it is worth checking the currents with a multimeter if you can.

The full circuit is shown in the diagram provided.