Safety Light for Bicycle Rear Portion

Safety Light for Bicycle Rear Portion

Safety Light for Bicycle Rear Portion #2
Part List
Circuit Project Description

The objective of the circuit is to produce a visible light that is clear enough to be seen with the use of 13 flashing LEDs while being power by 3 V battery source, which makes it suitable also for joggers and walkers.

Terminology TS555 – a single CMOS timer which offers very low power consumption and high frequency where the timing remains very accurate in monostable or astable mode while providing reduced supply current spikes during output transitions, which enables the use of lower decoupling capacitors and with added features of high output current capability, high input impedance, wide voltage range, and output compatible with TTL, CMOS & Logic MOS555 – a highly stable device for generating oscillation or accurate time delays used in pulse width/position modulation, sequential timing, time delay generation, linear ramp generator, precision timing, and pulse generation due to its features such as normally open and normally off output, temperature stability, output and supply TTL compatible, adjustable duty cycle, and operates in both astable and monostable mode Circuit Explanation

The arrangement of the highly efficient 13 LEDs is following the pseudo-rotating order for more visibility. The efficiency of its usage is due to the features such as low drain battery operation, small size, and low voltage. The circuit was constructed as an astable multivibrator since IC1 is a CMOS version of the 555 IC. With this mode of operation, it is generating a 50% duty cycle of continuous square wave or rectangular pulses at an approximate frequency of 4 Hz.

The Pin 3 of the 555 output contains the sinking current operation that is far better than sourcing during a 3 V supply. This is the reason why LEDs D1 to D6 are connected to the positive rail. A second 555 IC is provided in order to obtain an alternate flashing operation. This type of connection serves as a trigger with an inverter and driving the LEDs D7 to D12 while D13 is permanently at ON state. The circuit starts its operation by closing the contacts of the SPST slider switch. The 3 V battery source may use a two AA 1.5 V connected in series.

The arrangement of the LEDs is in a two series display with a center LED that is permanently ON. The alternate flashing of the two series of LEDs with this kind of arrangement provides the appearance of pseudo-rotation. The frequency of the flashing may be altered by changing the value of capacitor C1. Due to the nature of its use, to avoid unnecessary accidents, it is essential that the LEDs to be used should be of high quality and efficiency.


The flashing bicycle safety back light is very important especially for those riding at night. It can be fit not only on the back side of the bicycle but can also be hang on the waistband and be taken off easily when leaving the bicycle. Some safety lights are being placed on the wheels with a variety of colors while other designs have different light modes like the static, flashing, and running mode. They can also be used by explorers, tourists, walkers at night, miner, and fishermen at night as headlamps on the cap.

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