This simple traffic controller can be used to teach youngsters the fundamentals of traffic laws. The circuit (illustrated in Fig. 1) makes use of components that are easily obtainable. It is primarily composed of rectifier diodes (1N4001), a 5V regulator 7805, two timers IC 555, two relays (5V, single-changeover), three 15W, 230V bulbs, and various discrete components. Transformer X1 takes the mains electricity and steps it down to produce a secondary output of 9 volts and 300 milliamps. The output of the transformer is rectified by a full-wave bridge rectifier, which is comprised of the diodes D1 through D4, filtered by capacitor C1, and regulated by integrated circuit 7805. (IC1). IC2 is hooked up to function as a multivibrator, and its "on" and "off" periods, which each last about 30 seconds, are determined by the component values that are selected. The output of pin 3 of IC2 becomes high for a period of half a minute as soon as the

mains power is turned on. This, in turn, energizes relay RL1 through transistor T1, and as a result, the normally-open (N/O) contact on the relay causes the red light (B1) to illuminate. At the same time, the power from the mains is cut off to the pole where relay RL2 is located. Fig. 1: Traffic Controller Circuit System When the "on" time of IC2 comes to a conclusion, a high-to-low pulse is generated at its pin 3, which then triggers IC3 through C5. Because IC3 is programmed to operate as a monostable and has a "on" time of approximately 4 seconds, pin 3 of IC3 will maintain its high state for the duration of this time and will energize relay RL2 by means of driver transistor T2. Therefore, the amber lamp (B2) will light up for a total of four seconds. Following the expiration of the 4-second time period of timer IC3 at pin 3, the relay RL2 becomes de-energized, and the green lamp (B3) begins to glow for the duration of the remaining approximately 26-second 'off' period of IC2. The normally closed (N/C) contacts of relay RL2 are what are responsible for turning on the green bulb. Therefore, when the mains power is turned on, the red light will glow for 30 seconds, the amber light will glow for 4 seconds, and the green light will glow for 26 seconds. You can construct this circuit on a printed circuit board (PCB) designed for general use and then enclose it in an insulated box. In the box, there ought to be sufficient room for attaching both the X1 transformer and the two relays. Either it can be put on the PVC tube that was used in the building of the traffic signal container or it can be fixed close to a power supply that operates at 230V AC and 50Hz.

Figure 2 provides an illustration of the building of the traffic light container box. To house the lamps, you will need a sturdy cardboard box of 30 by 15 by 10 centimeters in volume. Use a piece of plywood with a surface area of 10 by 45 centimeters and a thickness of 1.5 centimeters. Place three light sockets and the box onto the plate, and then fasten them with nuts, bolts, or screws. Fig. 2: Construction of the traffic light container box Create three tubes out of the thin aluminum sheeting that can be found in most home improvement stores. It is recommended that the inner diameter of aluminum tubes be made to a size that allows them to fit securely on light sockets. Make holes carefully

on the other side of the sockets using a knife that is very sharp. Connect the wires to the sockets on the back, then thread them through the PVC tube to exit. Once that, you should press on the tubes after you have installed three 15W bulbs (B1 through B3). Place the remaining ends of the tubes in the holes that were cut out of the front panel of the cardboard box to provide support. Placing three sheets of colored gelatine paper between two pieces of cardboard and adhering them to the tubes will give you a rainbow effect. The mounting of the red, amber, and green lights on the tubular shape results in an improvement in the lights' visibility.