Photoelectric security circuit principle

Photocoupler

In the operation of electromechanical equipment such as motor-driven machine tools, in order to ensure the personal safety of the operator, the light control safety controller described below can be used.
As shown in the figure is an electrical schematic. The controller is mainly composed of a light source, a photodiode, a 555, and the like. The light source lamp ZD and the light human body mechanism 2CU1A are respectively placed on both sides of the safe area to be protected. When the power switch K is turned on and the power is turned on, the ZD1 emits light, and the light speed is concentrated on the 1CU1A through the convex lens. The photosensitive tube then produces a light source, and the voltage on pins 2 and 9 of 555 rises. When the voltage is higher than one third of the power supply voltage, the third pin of the 555 output is low. This is the third and first pins are turned on, the relay J1 is closed, the normally open contact J1-1 is closed, and the indicator light AD3 Light, indicating that the work is normal. At the same time, another group of normally open contact switch J1-2 of J3 is also closed to CJ. At this time, the operator presses the switch AN1, the magnetic starter CJ is closed, and CJ1 is self-locking, CJ1~CJ2 is connected to the motor M, normal Working.