Traffic light control circuit

As shown in the figure, this is the automatic control circuit of traffic lights at traffic intersections. The controller is mainly composed of four 555 (IC2~IC5) and some resistors and capacitors, which are connected end to end to form a four-stage monostable delay circuit. The input 8V voltage is stabilized by 78M05 to provide 555 with a power supply voltage of VDD=5V.

When the power is just turned on, the trigger pulse is delayed by the IC1 (CD4011) gate circuit and R1, C1, and then added to the IC2 pin ② after differentiation by C2, R22, triggering IC2 to output a high level and enter a temporary stable state. The duration of the temporary stable state depends on the position of K1, the delay td=1.1RC6, and the setting time is 60 seconds, 45 seconds, and 30 seconds respectively. When the temporary stable state ends, the IC2 pin ③ is a low level, which is differentiated by C3 and R23, and the falling edge triggers IC3 again, forming a second-level monostable delay. In this way, the timing is triggered in sequence to complete the cycle of green light on-yellow light on (8 seconds, 10 seconds, 12 seconds)-red light on (60 seconds, 45 seconds, 30 seconds).

This circuit is the control circuit and the monitoring display part in the command booth. If it is really used for traffic control, the control signal should be used to excite the solid-state relay and then drive the light bulb to work.

This controller connects four-level circuits end to end and triggers them in sequence with delayed triggering, so that the traffic lights display green-yellow-red (color) signals in sequence, directing pedestrians and vehicles to pass in an orderly manner at the crossroad I=1 (green) - reminding attention (yellow) - prohibiting passage (red).