| 摘要 |
a constant voltage section for, when a DC power voltage is positive, connecting an AC source to zener diodes, a first capacitor, a first diode, first and second resistances and second and third capacitors, and when the DC power voltage is negative, connecting the AC source to a second diode, the first and second resistances and the second and third capacitors; an AC detector for connecting the AC source to the PC4 terminal of a microprocessor via a fifth resistance so as to determine the polarity of the AC, connecting the AC to sixth and seventh AC division resistances, a sixth levelling capacitor and a forth diode so as to input the voltage subtracted from the DC power voltage by the sixth resistance to the seventh terminal of the microprocessor; a relay driver connecting the seventh terminal of the microprocessor to a relay coil via an eighth resistance and a first transistor and closing a relay switch when the voltage of the seventh terminal is low; a temperature sensor; a heater operation sensor; a heater controller; a key; a display; and a microprocessor.
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