The timer (U1) performs a dual task; controls the alarm trigger circuit and the input delay circuit. In this circuit, R1 is triggered by U1 through the second pin to maintain a high potential. A normally closed sensor switch S1 provides a positive voltage at the junction of R2 and C1, and LED1 illuminates. When S1 is turned on, both ends of C1 are at a high potential and are not charged. The alarm circuit formed by 555: Shenzhen Esun Herb Co.,Ltd. , https://www.szyoutai-tech.com
Industrial Router Crystal 3.2*2.5mm 3225 26M (26.000MHZ) 12PF 10PPM 20PPM 30PPM Photocoupler 