- on Home & Garden
- Published in issue 7/2012 on page 22
Bicycle Rear Light
one super LED and 10 components last 5 minutes
Fitting a bike with a rear light that stays on even when stationary is both useful and interesting – especially when it uses a circuit as simple as this.This project would stand a good chance of winning the prize for the smallest circuit in this edition. This is, moreover, the reason why it’s been chosen here, as Elektor has already published at least two or three versions that are more elaborate, but not necessarily any better. This version is stripped right down to the bare essentials, but stays on for 5 minutes.
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R1 = 47Ohm
R2 = 1.2kOhm
C1 = 1F 5.5V, e.g. Panasonic EECF5R5H105
D1 = LED, red, standard (Vf = 1.7V)
D2 = zener 5.6V 3W
D3 = LED, red, high brightness, e.g. MCL034URC (Imax = 20 mA)
D4–D7 = 1N4004
T1 = BC547B
Elex-1 (UPBS-1) prototyping board