As shown, the proximity switch 555 as the core component monostable trigger circuit. 555 Trigger Pin 2 through the large resistance R2 connected to VDD, is waiting for a trigge
r condition. When the body close to or touch the metal plate electrodes, since the sensor signal 555 is triggered, a one-shot pulse output. C2 filtering for interference. The circuit can be used for electrical appliances, toys or alarm circuit.