| 摘要 |
A forced air gas heating furnace system includes a thermostat having a transformer for converting the typical household 115Vac to a 24V thermostat ac control voltage, and a switch, the thermostat elements connected to the junction of an ac to dc converter, a digital control circuit and a TRIAC. The dc output is connected to a dc voltage regulator which outputs Vcc for a digital control circuit. The gate of the TRIAC is connected to the output of the digital control circuit, and operates in response thereto for selectively triggering the TRIAC for passing the 24Vac transformer control power to a solenoid operated gas valve. The solenoid gas valve is connected between the gas source and the gas burner to control the gas supply to the burner in response to the digital control circuit signal operation of the TRIAC; first on to heat the furnace heat exchanger to an operating temperature, and thereafter off and on for selected periods necessary to maintain the operating temperature of the heat exchanger while conserving gas. The control circuit includes a square wave generator for converting the thermostat 60 Hz 24Vac to square waves for a counter/divider. The counter/divider generates pulses suitable for counters of a dual binary counter counting the pulses for outputting selected timing control signals to a logic circuit (plurality of NOR gates). The logic circuit outputs high/low state signals to a TRIAC driver (opto-coupler) which drives the TRIAC in response to the high/low state output of the logic circuit for controlled operation of the gas furnace.
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