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 bicyc
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.
Circuit operation:
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.
LED arrangement:
Notes:
Flashing frequency can be varied changing C1 value.
