Steam iron automatic protection circuit diagram

The automatic protection circuit of the steam iron is as shown in the figure. After the mains power is stepped down by C5, R7 and R8, rectified by VD7~VDl0 and stabilized by VD11, it provides the working voltage for the circuit. When the electric iron is placed horizontally, the mercury switch S is tilted downward about 15 degrees and is in the off state. At this time, IC1-a outputs low level , C1 is charged through R2, ICl-c outputs low level, ICl-d also outputs low level, and the NAND gate composed of VD3, VD4, and IC1-e outputs high level, VT2 is turned on, relay Jl is closed, the heating wire heats up, and the neon lamp H lights up. At the same time, ICl-f outputs low level, the oscillator does not work, and the LED light does not light up. After T1=0.7R2C1=35 seconds, the output status of IC1-c~ICl-f flips, the heating wire is powered off, and H goes out. ICl-f outputs high level, the oscillator oscillates, the buzzer alarms, and the LED flashes to avoid excessive temperature and scalding of clothes. Raise the front of the iron about 15o, or move it forward and backward, turn on the mercury switch, and then return it to the horizontal position, and the iron will return to its original working state. When ironing clothes, the forward and backward movement of the iron is enough to frequently turn the mercury switch on and off, and the cycle is much less than 35 seconds, thus ensuring that the iron is always uninterrupted. If you need to pause during the ironing process, just put the iron upright. At this time, the mercury switch is turned on, ICl-a outputs high level , and charges C2 through VDl and R2, while the output of the subsequent circuit will maintain the initial working state. constant. After T2=0.7R2C2=5.5min, the output status of ICl-b and ICl-f changes, relay J1 is released, the heating wire is powered off, the oscillator works and sends out an audible and visual alarm signal.

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The IC in the circuit uses CD 40106B, 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 the LED is not limited.