This helmet light set up is cheap, easy to build and works quite well.
Step 1: Materials
1 qty helmet
3 qty 12v automotive taillight bulbs LED #3156 others will work also but that is what I used. (2) white (1) red. I got my from: http://superbrightleds.com/
1 qty small length of adhesive backed velcro (hook and loop fastener)
10 qty zip ties
1 qty small length of speaker wire or similar
1 qty small piece of metal, plastic or other stiff material for battery backer
2 qty 9v batteries best if rechargeable
1 qty old bike inner tube
1 qty small switch
1 qty small length heat shrink tubing
2 qty wire nuts
1 qty 9v battery plug. Available at any electronic supply store or salvage from and old toy or electronic device.
Drill and Bits
Step 2: Assembly
Solder wire leads to the end of the bulbs. They will only work one way so test your polarity before final solder. I ride rain or shine so I put some water proofing over them. I put a small length of bike inner tube with a little heat shrink tube to keep it tight.
I scavenged a 9v battery plug and a small switch from an old toy train my kids had broken. The 9v plug was separated so the + and - could be put in different places. I soldered pig tails of wire to the switch and the 9v battery plug parts.
I drilled a few holes in the piece of metal and zip tied it to the back of the helmet. This is the backer for the batteries. I put velcro on the batteries and a loop around for good measure. You will notice the batteries are plugged end to end creating a series and results in 18 volts. That is why the plug had to be separated in to two.
Once all the parts were prepped I put small pieces of velcro on the bulbs, batteries and switch. The two white bulbs face the front and the one red faces the back. After some trial and error I mounted all the parts. Once finalized the position of every part I zip tied over the velcro just for good measure.
Finally the wires were trimmed to length and wire nutted together. The wiring is simple; all the white wires go to + side of the battery supply, all of the black wires from the bulbs go to one side of the switch, then the wire from the - side of battery pack goes to the other side of the switch.
Step 3: Results
The weight of the batteries on the helmet is enough for you to definitely feel. After a couple rides I got used to it. Now it is normal to me.
The light is very bright and works well. I try to be careful not to tilt my head up too high while on the road. Running them over the 12 volts really cranks out a blinding beam.
I thought I might have a durability issue with the bulbs running over 12 volts but it has been several months of use with no failure yet...
It is hard to take a good picture with my camera but you get the idea. Nice and bright.