Power supply undervoltage and overvoltage alarm protector circuit design

　　Circuit function: When the voltage is lower than 180V or higher than 250V, it can give an audible and visual alarm. When an AC contactor is connected externally, it can cut off the power supply to protect electrical equipment.

　　Circuit principle:  When the input power supply voltage is normal, Y1A outputs high level, Y1B outputs low level, the light-emitting diode LED and the oscillating sound circuit Y1C, Y1D and the speaker do not work, and the control component J1 does not work. When the voltage is higher than 250V or lower than 180V, Y1B outputs high level, the light-emitting diode is on, the oscillating sound circuit works, emits a chirping sound, and controls the transmitter J1 to close. When the normally open contact of J1 is connected to an AC contactor, the main circuit can be controlled to disconnect the power supply.

　　Debugging method:  The first step is to adjust W1 so that the output of Y1A changes from a low level to a high level when the input power voltage is 250V. The second step is to adjust W2 so that the output of Y1B changes from a high level to a low level when the input voltage is 180V.