Bicycle Safety Light
Here's another design from Red Circuit Designs:
Flashing 13 LED unit, 3V supply
Also suitable for jogger/walkers
|C1||1µF||63V Polyester Capacitor|
|C2||10nF||63V Polyester Capacitor|
|C3||100µF||25V Electrolytic Capacitor|
|D1-D13||Red LEDs||5mm. or bigger, high efficiency|
|IC1,IC2||7555||or TS555CN CMos Timer|
|IC SW1||SPST||Slider Switch|
|B1||3V Battery||(2 AA 1.5V Cells in series)|
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/walkers.
IC1 is a CMOS version of the 555 IC wired as an astable multivibrator generating a 50% duty-cycle square wave at approx. 4Hz frequency. At 3V supply, 555 output (pin 3) sinking current operation is far better than sourcing, then LED D1-D6 are connected to positive supply. 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.
The LEDs are arranged in a two series display as shown below, with a center LED permanently on. This arrangement and the alternate flashing of the two series of LEDs provide a pseudo-rotating appearance.
- Flashing frequency can be varied changing C1 value.
- High efficiency LEDs are essential.