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Build a Rotating Back Light: 555 Timer Circuit Diagram
Description
This circuit has been designed to produce a discernible illumination, consisting of thirteen high-performance flashing LEDs arranged in a simulated-rotating sequence. Owing to its low voltage operation and compact size, the device is suitable for attachment to bicycles as a rear light, or for use by joggers and pedestrians. IC1 represents a CMOS variant of the 555 IC, configured as an astable multivibrator, generating a 50% duty-cycle square wave at approximately 4Hz.
At a 3V power supply, the 555 output (pin 3) employing a sinking current approach offers superior performance compared to sourcing, and the LEDs D1-D6 are connected to the positive supply rail. To achieve an alternative flashing effect, a second 555 IC is supplied, functioning as a trigger and inverter, and driving LEDs D7-D12. D13 remains continuously illuminated. The LEDs are arranged in a two-series display as shown below, with a central LED consistently on. This configuration and the alternating flashing of the two series of LEDs create a simulated-rotating appearance.
Circuit diagram:
Parts:
- R1 = 10K
- R2 = 100K
- R3 = 10R
- R4 = 10R
- R5 = 10R
- R6 = 10R
- R7 = 10R
- R8 = 10R
- R9 = 100K
- R10 = 100K
- R11 = 10R
- R16 = 10R
- R17 = 150R
- C1 = 1µF-63V
- C2 = 10nF-63V
- C3 = 100µF-25V
- B1 = 3V Battery (2 AA 1.5V Cells in series)
- SW1 = SPST Slider Switch
- D1-D13 = Red LEDs 5mm. or bigger, high efficiency
- IC1-IC2 = 7555 or TS555CN CMos Timer IC
LED arrangement:
Notes:
- The flashing frequency can be altered by modifying the value of C1.
- High-performance LEDs are crucial for optimal operation.
Integrated Circuits (ICs) play a crucial role in this circuit. The 7555 or TS555CN IC, commonly referred to as a CMOS Timer IC, is a versatile component employed as an astable multivibrator. This IC functions as the heart of the flashing mechanism, generating the precise square wave signals that control the LEDs. It incorporates a built-in oscillator and comparator, simplifying the circuit design and contributing to its stability. The TS555CN variant offers enhanced noise immunity compared to the original 555 timer, providing greater reliability in varying environmental conditions. The IC's pins provide several functionalities, including a power supply pin, a reset pin, and output pins for generating the timing signals. These features make it a preferred choice in applications needing predictable and stable timing characteristics.