Bike Turn Indicator using IC555

Circuit Design:

1. 555 Timer Connections:
   • Connect the VCC pin (pin 8) of the 555 timer to the positive supply voltage (e.g., 9V).
   • Connect the GND pin (pin 1) of the 555 timer to the ground (0V) of the circuit.
2. Astable Mode Connections:
   • Connect the trigger input (pin 2) to the discharge pin (pin 7).
   • Connect the discharge pin (pin 7) to the capacitor side of a resistor-capacitor series.
   • Connect a resistor (e.g., 10kΩ) from the trigger input (pin 2) to the positive supply voltage.
   • Connect a capacitor (e.g., 10μF) from the trigger input (pin 2) to the ground.
   • Connect the other end of the capacitor to the discharge pin (pin 7).
3. Transistor Drivers:
   • Connect the collector of NPN transistors (e.g., 2N3904) for the left and right indicators to the output pin (pin 3) of the 555 timer.
   • Connect the emitters of the transistors to the ground (0V).
   • Connect the bases of the transistors through current-limiting resistors (e.g., 1kΩ) to the output pin (pin 3) of the 555 timer.
4. LEDs and Diodes:
   • Connect the anodes of the left and right LEDs to the collectors of their respective transistors.
   • Connect the cathodes of the LEDs to the positive supply voltage through current-limiting resistors (e.g., 330Ω).
   • Connect diodes (e.g., 1N4148) in parallel with each LED to protect against reverse voltage.
5. Activation Switches:
   • Connect normally open (NO) push-button switches for left and right turns to the trigger input (pin 2) and ground.

Working Principle:

• The 555 timer is configured in astable mode, generating a continuous square wave at the output (pin 3).
• When the left or right turn switch is pressed, the corresponding transistor is activated, allowing current to flow through the respective LEDs, creating a flashing pattern.