Simple traffic light controller circuit diagram sharing

Here is a simple traffic light controller that can be used to educate kids about the basic principles of traffic light guidelines. The circuit makes use of easily available electronic parts. It usually consists of a rectifier diode (1N4001), a 5V regulator 7805, two timer circuits using IC555, two relays (5V, single conversion), three 15W, 230V bulbs, and a few discrete parts.

The primary power is stepped down by transformer X1 to provide a secondary output voltage of 9V, 300mA–AC. The transformer output current is then rectified by a full-wave bridge rectifier consisting of diodes D1 to D4, filtered by capacitor C1, and regulated by IC7805 (IC1).

IC2 is wired as a multivibrator with an "on" and "off" cycle of about 30 seconds, with the values ​​of the various parts determined. Once the main power switch is turned on, pin 3 of IC2 will go high for 30 seconds. This in turn powers relay RL1 through transistor T1, and the red bulb (B1) glows through its normally open (N/O) contact. At the same time, the mains is disconnected from the pole of relay RL2.

As IC2's "on" time is over, a triggers IC3 via C5. IC3 is set up as a monostable and the "on" time is about 4 seconds, which means that pin 3 of IC3 will remain high during this time and energize relay RL2 via driving transistor T2. Therefore, the amber bulb (B2) lights up for 4 seconds.

After the 4-second time period of timer IC3 at pin 3 has expired, relay RL2 is immediately de-energized and the green bulb (B3) illuminates for the remainder of IC2's "off" cycle (approximately 26 seconds). The green bulb is turned on by the normally closed (N/C) contacts of relay RL2.

So when the power switch is turned on, the red light will be on for 30 seconds, the yellow light will be on for 4 seconds, and the green light will be on for 26 seconds.

You can easily build this circuit on a general-purpose PCB and enclose in a protected box. The box needs to have enough space to mount the transformer X1 and two relays. It can be mounted near a 230VAC, 50Hz power supply or mounted on a PVC pipe used for traffic light box assembly.

The design of the traffic light container box is shown in the figure below:

You will need a 30x15x10cm3 rough cardboard box to hold the lights in. To get some durability use a 10x45cm2 sheet of plywood with a thickness of 1.5cm and fasten the three light outlets and the box to it using nuts and bolts or screws.

Make three tubes of thin aluminum sheet, which is easily available in equipment stores. The inner diameter of the aluminum tubes should be such that these can fit well into the light outlets. Use a sharp knife to carefully make holes opposite the outlets. Connect the outlets on the back and run the cables through the PVC tubes.

First, secure the three 15W bulbs (B1 to B3) and then press the tube. Support the other end of the tube in the hole on the front panel of the cardboard box. Sandwich the three colors of gelatin paper between the two pieces of cardboard and secure it to the tube. The visibility of the red, amber, and green lights is enhanced as they are mounted on the tubular form.