LCD-LED Display

Bike Turning Signal Circuit

In this project, I will show you how to design a simple Bike Turning Signal Circuit using 555 Timer IC, couple of LEDs and a few other easily available components.

Bike Turning Signal Circuit


  • Introduction
  • Bike Turning Signal Circuit Principle
  • Bike Turning Signal Circuit Diagram
  • Circuit Components
  • Bike Turning Signal Indicator Circuit Design
  • How to Operate the Circuit?
  • Applications of Bike Turning Signal Indicator Circuit


Turn Indicator Lights, also known as Directional Indicators (officially) or Blinkers, Flashers (informally), are a necessary component of all autos, whether they are motorcycles or automobiles. They let other drivers know whether we intend to turn left or right. When developing and integrating Turn Lights into a vehicle, manufacturers must adhere to a number of regulations and requirements.

Bike Turning Signals are used to communicate the intention of making a left or right turn to other road users. Have you ever attempted to create a set of bike turn indicators? This article will show you how to make these bicycle turn signals.

Bike Turning Signal Circuit Principle

The goal of this circuit is to indicate whether a bike or car should turn left or right. The 555 Timer IC is the essential component of this circuit. This 555 timer is used as an Astable multi vibrator in this example. It generates a variable-width pulse signal. We can set different time delays for the LEDs by varying the pulse width (ON and OFF for LEDs).

Two crucial resistors (100K and 470K) are linked to the 555 timer and are used to set the time delay for LEDs in the circuit. A Slide Switch directs the output of the 555 Timer IC to either the LEFT or the RIGHT indication LED.

To maintain constant current at the output, a 1n4148 signal diode is connected in reverse bias. Based on the base currents, the BC547 (NPN) Transistor turns the LEDs on and off. To lower the voltage, 330 ohm resistors are needed; otherwise, LEDs may be destroyed. By changing the resistance or capacitance value, we may change the temporal breadth of the output pulse.

Bike Turning Signal Circuit Diagram

Circuit Components

  • Resistor 180Ω
  • Resistor 100KΩ
  • Resistor 470KΩ
  • Capacitor 1µF
  • 555 Timer IC
  • LEDs – 2
  • Diodes (1N4007) – 2
  • SPDT Slide Switch
  • 9V Battery
  • Connecting Wires
  • Breadboard

Bike Turning Signal Indicator Circuit Design

The 555 timer generates a pulse signal with variable width in this circuit. Varying the resistance or capacitance value (100K, 470K, or 1F) changes the pulse width. To allow triggering after each timing cycle, pins 2 and 6 are shorted.

To avoid unexpected resets, the fourth pin is shorted with VCC (8th pin). The 7th pin is the discharge pin, and it is connected to the 6th pin through a 470K resistor. The 555 timer is demonstrated in the diagram below. Capacitor C is charged in this circuit via resistors RA and RB. Capacitor C now discharges through resistor RB due to internal op-amps. Internally, the 555 timer is made up of two operational amplifiers, one D flip flop, and one NPN transistor.

In the above circuit, the pulse is generated at the 3rd pin of the 555 timer. By varying the values of RA, RB or C, we can vary the pulse width. The total time period of the pulse is given as

T = THIGH + TLOW = 0.693 (RA+ 2RB) C

 Frequency of the pulse is given as

f = 1/T = 1.44/ (RA+ 2RB)C

percentage of duty cycle is given as

% duty cycle, D = t/ T * 100 = (RA + RB) / (RA + 2RB) * 100

The 555 timer’s output pulse is applied to the LEDs through the slide switch, which turns them on and off with a delay. The operational voltage of the LEDs is roughly 2 to 3 volts, however we obtain 9 volts from the battery. As a result, we must lower the remaining voltage. We’re utilising resistors in series with LEDs to lower the voltage.

How to Operate the Circuit?

  • Initially, supply the circuit with a 9V power supply.
  • When you slide the switch to the left, the LEFT Indicator LED will begin to blink with a slight delay.
  • The RIGHT Indicator LED will blink if you slide the switch to the right position.
  • Both LEDs will be turned off if you slide the switch to the centre position.
  • Set alternative LED time delays if desired, then change the resistance or capacitance value.
  • You can now observe the difference in time delay.
  • You can see the in time delay of LEDs by altering the capacitance value.

NOTE: Since this is a demonstration, I have used only one LED per channel (LEFT and RIGHT). But if you want to integrate several LEDs per channel, you can do that with the help of a Transistor on each channel and sufficient power supply.

Applications of Bike Turning Signal Indicator Circuit

  • It is used to indicate left turn or right turn for a motor bike or vehicle.
  • We can also use this circuit as an LED knight rider circuit.
  • We can give it as a gift for the children.


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