How to Set up a traffic light circuit and how it works

traffic light circuit

In model making, a traffic light circuit that is as easy to set up as possible is often required. You can build this yourself on a small circuit board using standard electronic components.

What you need:

  • an integrated circuit 4017
  • IC socket, 16-pin
  • two transistors BC 547
  • three transistors BD 679
  • eleven diodes 1N4148
  • two electrolytic capacitors 10 microfarads
  • a potentiometer 100 kilohms
  • three resistors 1 kilohm
  • a resistor 12 kilohms
  • three resistors 470 ohms
  • a breadboard (size about 50 x 100 millimeters)
  • connecting wire
  • three 12 volt lamps or model traffic lights with built-in lamps
  • Soldering iron and solder
  • side cutters
  • Voltage source 12 volts

The function of the traffic light switch

This traffic light circuit consists of an integrated circuit and some additional discrete components.The integrated circuit is a counter module. This is controlled by a so-called astable multivibrator, which acts as a clock generator here.

With each cycle, the integrated circuit counts one step further. This controls different outputs at the output of the circuit.

The outputs of the traffic light circuit are controlled by the diodes at the output of the integrated circuit and the subsequent transistors.

As a result, the lamps at the exit light up in such a way that they represent the typical lighting sequence of a traffic light.

With the potentiometer (potentiometer) in this circuit, the time for a complete run through of the individual traffic light phases can be varied.

This is how you build the circuit according to the circuit diagram

You can use a small breadboard to set it up. It is best to use an appropriate IC socket for the integrated circuit.

  1. Begin by first inserting the IC socket into the breadboard and soldering it. To do this, it is best to place the base in the middle of the circuit board. However, do not insert the integrated circuit into the socket yet.
  2. Then insert the other electronic components into the circuit board and solder them as well. Always pay attention to the correct polarity of the components.
  3. Now connect the components according to the circuit diagram . For this you can use simple connecting wire or solder bridges made of solder.
  4. Finally, when you have built the circuit this far, you can insert the integrated circuit into the socket. However, make sure that the installation position is correct.
  5. Set the potentiometer to the middle position before starting up the traffic light circuit.
  6. Now connect the board to a suitable power supply. If you have set everything up correctly, the traffic light should now work.
  7. With the potentiometer you can adjust the time for a complete run to your wishes.