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Bike Tail Light with Standlight

Be seen even at standstill!

Bike Tail Light with Standlight
As autumn approaches cyclists become more aware of safety and in particular their visibility to other road users. Dynamo lighting offers the cheapest running costs but has the disadvantage that when the wheels stop rolling the lights go out. This neat circuit stores energy while you are moving to keep the light shining even when you stop.It is not too difficult to construct a simple and reliable rear light unit for a cycle dynamo using high visibility LEDs. They have a much longer lifespan than filament lamps and this design uses a high value capacitor to store enough energy to keep the lamp burning for a few minutes after the cycle has come to a standstill.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor Members can exclusively download these files for free as part of their Membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service. Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

R1 = 12Ohm
R2 = 1kOhm
R3 = 3kOhm 9
R4 = 27Ohm
R5 = 390Ohm
R6 = 150Ohm 1W
C1 = 100µ F 35V radial
C2 = 22µ F 16V radial
C3 = Goldcap 1F /5.5V (Conrad Electronics # 473120)
B1 = B80C1500, round case (80V iv, 1.5A)
D1,D2 = LED, red, 3mm, Kingbright L-934SRC-J (Reichelt, LED 3-3500RT)
D3 = LED super-red, 8 mm, Kingbright L-793SRC-F (Maplin # N46AT)
D4,D5 = 1N4148
D6 = zener diode 6.2V, 500mW
T1,T2 = BC547B
Bike rear light case, Busch & Müller type 339, www.bumm.de/docu/ruecklicht1.htm (UK distributor: Amba Marketing)
PCB, available from the PCBShop
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