Steam iron automatic protection circuit

The circuit is shown in the figure. The mains power is stepped down by C5, R7, R8, rectified by VD7~VDl0 and stabilized by VD11 to provide the circuit with working voltage. When the electric iron is placed horizontally, the mercury switch S tilts downward by about 15 ^degrees and is in the disconnected state. At this time, IC1-a outputs a low level, C1 is charged through R2, ICl-c outputs a low level, ICl-d also outputs a low level, the NAND gate composed of VD3, VD4, and IC1-e outputs a high level, VT2 is turned on, relay Jl is energized, the heating wire heats up, and the neon lamp H lights up. At the same time, ICl-f outputs a low level, the oscillator does not work, and the LED light does not light up. After T1= 0.7R2C1=35 seconds, the output state of IC1-c~ICl-f flips, the heating wire is powered off, and H turns off. ICl-f outputs a high level, the oscillator oscillates, the buzzer alarms, and the LED flashes, thereby avoiding excessive temperature and damaging the clothes. Lift the front of the electric iron by about 15 ^degrees , or move it back and forth, turn on the mercury switch, and then put it back to the horizontal position, and the iron will return to its initial working state. When ironing clothes, the forward and backward movement of the iron is enough to make the mercury switch frequently turn on and off, and the cycle is much less than 35s, thus ensuring that the iron is always powered on. If you need to pause during the ironing process, just stand the iron upright and place it. At this time, the mercury switch is turned on, ICl-a outputs a high level, and charges C2 through VDl and R2, while the output of the subsequent circuit will remain unchanged in the initial working state. After T2=0.7R2C2=5.5min, the output states of ICl-b and ICl-f change, relay J1 is released, the heating wire is powered off, the oscillator works and sends out an audible and visual alarm signal.

The IC in the circuit uses CD40106B, VT1 uses 9014, VT2 uses N2222A, VD1~VD6 uses 1N4148, VD7~VD10 uses 1N4007, VD11 uses 13V, 1W voltage regulator tube, relay J1 uses 12V, contact 6A, and LED is not limited.