Commuting and Trail Riding Bicycle Helmet Lighting Solution...

Step 4 Assemble electronics

The hardest part of the electronics was knowing that they had to fit inside the clear tube ordered from Ebay.

The 200 Lumen LED's have a Vf of ~ 3.7v, The Buckpuck has an equivalent Vf of ~ 2v. Each of the 100 Lumen white and red LED's have a Vf of ~ 3.4v. The Front segment consists of the two 200 lumen LED's wired in series. The rear strobe segment consists of two 100 lumen white and 2 100 lumen Red LED's wired in series. The two front 100 Lumen white LED's are selectable between front and rear, extending the respective circuit by two additional LED's. The voltage required for each segment is as follows:
Front segment
3.7+3.7+2.0 = 9.4v
with 100 lumen LED's
3.7+3.7+3.4+3.4+2.0 = 16.2v

Rear segment
3.4+3.4+3.4+3.4+2.0 = 15.6v
with 100 Lumen LED's
3.4+3.4+3.4+3.4+3.4+3.4+2.0 = 22.4v

Therefore, the battery pack needs to be greater than 22.4v. You will later see that I decided on two Macbook pro extra batteries that I keep on hand for traveling. The are Lithium Ion with good discharge capability 10.8v, measured at 14.1v, long life, 60 Wh or ~5555ma, and the best feature of all, a built in battery level indicator.

Each of the LEDs were ordered bare. I had to hand solder each to the star base I ordered from Dealxtreme. I put a little bit of nonconductive Thermal paste on the base of the LED which was connected to the cathode, just to make sure I didn't end up with a short.