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Bicycle back Safety Light

Bicycle back Safety Light

This circuit has been designed to provide a clearly visible light, formed by 13 high efficiency flashing LEDs arranged in a pseudo rotating order. Due to low voltage, low drain battery operation and small size, the device is suitable for mounting on bicycles as a back light, or to put on by jogger or walkers.
IC1 is a CMos version of the 555 IC wired as an astable multivibrator generating a 50% duty-cycle square wave at about 4Hz frequency. At 3V supply, 555 output (pin 3) sinking current operation is far better than sourcing, then LEDs D1-D6 are connected to the positive supply rail. In order to obtain an alternate flashing operation, a second 555 IC is provided, acting as a trigger plus inverter and driving LEDs D7-D12. D13 is permanently on.

R1_____________10K 1/4W Resistor:
R2,R9,R10_____100K 1/4W Resistors:
R3-R8,R11-R16__10R 1/4W Resistors:
R17___________150R 1/4W Resistor:
C1______________1µF 63V Polyester Capacitor:
C2_____________10nF 63V Polyester Capacitor:
C3____________100µF 25V Electrolytic Capacitor.

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