Touch delay switch

The light touch delay switch is designed using conventional rectifier bridge, transistor, thyristor, capacitor and resistor, and the circuit is simple and reliable.
It adopts two-wire wiring and 86 switch panel design, making it easy to replace ordinary switches.
There is an LED indicator light to facilitate finding the switch in the dark.
 
The 220V AC power supply is connected in series through the electric lamp (the light bulb is not shown in the schematic diagram), and is converted into DC through the rectifier bridge D1.
In the initial state, the capacitor C1 is not charged, the transistor Q2 is turned off, the thyristor D2 is turned on, and the light is on.
After a period of time, the capacitor C1 is charged, the voltage rises, the transistor Q2 is turned on, the thyristor D2 is turned off, the light goes out, the DC voltage rises after rectification, and the indicator light U1 lights up.
When the pole piece J3 is touched, the voltage induced by the human body turns on the transistor Q1, the capacitor C1 is discharged, the circuit returns to the initial state, and the lamp lights up.
 
The multiple resistors in the circuit are connected in series to consider the voltage resistance and safety of the 0805 chip resistor.
The position of the indicator light has solder-resist windows on both sides, taking advantage of the light-transmitting properties of the PCB substrate. Note that the LED must be pasted backwards.
 
Video demonstration:
[Touch delay switch] https://www.bilibili.com/video/BV1gR4y167ff/?share_source=copy_web&vd_source=9c5db5a943feee800a75f29c11f5b13b