Cyclist’s Safety Light Circuit – Nighttime Visibility for Cyclists, Walkers, Joggers

A simple flashing bicycle safety light circuit has been discussed in the following article

In many occasions when we happen to go down the road at night, it is normal to meet cyclists that are visible only when they might be within walking distance.

In case you're a bike aficionado and prefer to stroll in the dark or overnight, this rider's safety light circuit can be very useful, since it will likely be easily observable.

Circuit Operation

We have observed designs that are based on two integrated circuits 555 and 12 diodes LEDs red, but I was able to modify the design to use only 555. With this particular new made it was easy to double on the 2 groups design. LEDs (see diagram) really do not persist the same time, but that does not create much of  a problem.

Operational details of the bicycle safety light circuit

Utilizing only one circuit 555, it could be configured as an astable multivibrator (having a square waveform) for the operations.

This circuit will have two groups of 6 LEDs each.

The top group of 6 LEDs will light any time the output of 555 is low (approximately 0.75 volts) and the top group would probably switch on when the output of 555 is high (approximately 8.4 volts

This alternating light motion is very spectacular and very hard to overlook the night.

LEDs can be placed in various different optional ways:

- Two rows of LEDs as shown in the diagram,
- Two rows interspersed with LEDs, and therefore the first group is switched on but with 3 up and 3 down and then in the second group, etc..

This circuit was created to be used with a PP3 9 volt battery

Circuit Diagram

Parts list for the discussed bicycle safety light

IC1: 555 timer
D1 through D12:  red LEDs  5mm
R1: 10K resistor
R2: 100K resistor
R3 to R14: 1K 1/4 watt
C1: 10uF/25V