Electric blanket cycle timer circuit

Circuit working principle: When the circuit is connected to the mains power, R. , C, resistor-capacitor current limiting buck
, VD. One VD4 rectifies and C2 filters to obtain +12 V DC, which
supplies power to Ic, and relay K. The switch S on pin 4 of Ic is a single-pole single-throw switch , which is not turned on at ordinary times.
According to the NE555 circuit principle, the NE555 circuit does not work when pin 4 is not connected to high potential , that is,
pin 3 outputs low level, K pulls in, and K ． ． , closed, the electric blanket is heated electrically. At this time, the delay
on/off circuit does not work. Only when the person is sleeping and feels that the temperature of the electric blanket
meets the needs, S will be closed, and the circuit will automatically delay on/off. The power-on time
is determined by R4, C3, Rs, RP, VDs, etc., and the range can be set from 5min to th. The shutdown
time is determined by R4, VDs, RP2, and C3, and the range can be set from 5 minutes to th.