Long delay dual-purpose timer circuit based on 555 integrated chip design

The 555 timer has two comparators, A1 and A2, with an RS flip-flop, and R and S are active high. Transistor VT1 plays a buffering role in clearing. Transistor VT2 is a discharge tube that provides a discharge path for components of the external circuit. The input of the comparator has a voltage divider consisting of three 5 kW resistors, from which two partial voltage values ​​can be obtained, commonly referred to as threshold values. The 1 pin of the 555 timer is the ground GND, the 2 pin is the low trigger terminal TL, the 3 pin is the output terminal OUT, the 4 pin is the clear terminal Rd, the 5 pin is the voltage control terminal CV, and the 6 pin is the high trigger terminal TH, 7 The foot is the discharge terminal DIS, and the 8 pin is the power terminal VCC. The output of the 555 timer can reach 200mA, so it can directly drive loads equivalent to this current value, such as relays, speakers, LEDs, etc.
Adjusting the potentiometer W changes the magnitude of the FET drain current ID, thereby changing the charging rate of the capacitor C1. So adjust the potentiometer to change the length of the timing. The larger the resistance of the potentiometer, the larger the adjustment range.