NE555 Hand-touch timed water supply faucet

As shown in the figure, this is a hand-touch timing water supply control valve circuit. The control valve consists of a step-down rectifier circuit, a bistable trigger circuit IC2-1 (1/2556), a timing circuit IC2-2 (1/2556), and a relay control circuit. The step-down rectifier circuit provides a DC voltage VDD = +12V for IC1 (IWH8778), IC2 (556), etc. When the metal sheet M2 is touched, the bistable trigger circuit composed of IC22-1 and C2, C3, D12, and D13 flips, and the high level output by the ⑤ foot turns BG2 off, BG1 turns on, and lights up LED2, thereby flipping the monostable timing circuit IC2-2, and the timing time is td = 1.1 (R3 + Rw1) C6. The high level output by the ⑨ foot of IC2-2 turns on the power switch tube of IC1, the relay J is attracted, the contact of J1-1 is closed, and the solenoid valve DF is energized to open and release water. When the timing time is up, IC1 is turned off and the water discharge stops. When the switch K is turned to "2", it is in the manual water discharge state. When it needs to be turned off, touch M2 to stop the water discharge.