Bicycle Back Safety Light Circuit Schematic Circuit

Description: This circuit is designed to provide a clearly visible light using 13 high-efficiency flashing LEDs arranged in a pseudo-rotating manner. Its low voltage, low battery drain operation, and compact size make it suitable for mounting on bicycles as a backlight or for use by joggers and walkers. The circuit employs a CMOS version of the 555 timer IC, configured as an astable multivibrator, which generates a 50% duty-cycle square wave at approximately 4 Hz frequency. At a 3V supply, the output (pin 3) of the 555 timer performs better in sinking current than sourcing it, leading to the connection of LEDs D1-D6 to the positive supply rail. To achieve an alternate flashing operation, a second 555 timer IC is included, functioning as a trigger and inverter for driving LEDs D7-D12, while LED D13 remains continuously illuminated. The LEDs are organized in a two-series display with the center LED always on, creating a pseudo-rotating effect through the alternating flashing of the two series.

The circuit utilizes two 555 timer ICs, which are crucial for generating the desired flashing pattern. The first 555 timer operates in astable mode, producing a square wave signal that alternates the current through the first set of LEDs (D1-D6). This configuration allows for a consistent flashing rate, which is adjustable by modifying the resistor and capacitor values connected to the timer. The choice of a CMOS version of the 555 timer ensures low power consumption, making the circuit ideal for battery-operated applications.

The second 555 timer IC is configured to act as a trigger and inverter. This setup allows for the alternate activation of the second set of LEDs (D7-D12), which enhances the visual effect by creating a rotating light pattern. The inclusion of LED D13, which remains constantly lit, serves as a visual anchor in the center of the display, further enhancing the pseudo-rotating appearance.

The arrangement of the LEDs in two series not only contributes to the aesthetic effect but also ensures that the light output is sufficiently bright for visibility during low-light conditions. The circuit's design considerations, including component selection and arrangement, are tailored for optimal performance in portable applications, making it suitable for various outdoor activities. The overall simplicity of the circuit allows for easy assembly and integration into existing systems, such as bicycle lighting or personal safety gear for joggers and walkers.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 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. 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.