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Temperature control principle shown in Figure 2 .
Analysis: change in temperature of the temperature control circuit using a thermistor Rt is converted into a voltage signal, and then via a resistor divider R234 , R240 limiting . This signal is compared with the reference signal microcontroller to control the opening stop of the compressor. Capacitor C218 is used to prevent excessive voltage changes . Rt is a negative temperature coefficient thermistor , the thermistor value usually means 25 ¡æ obtained when the measured resistance .
Pipe temperature control principle in Figure 3.
Analysis: indoor pipe thermal sensitive resistors mounted on the pipe of the indoor evaporator , the measured temperature is close to the evaporation temperature of the refrigeration system , and its effects: ( 1 ) for winter heating control of the anti- cold ; ( 2 ) for refrigerant subcooling summer control ; ( 3 ) is used to control indoor wind ; ( 4 ) and SCM with the realization of fault diagnosis .
Maintenance Analysis:
1 . This failure rate is higher Rt thermistor circuit , generally the first to measure its resistance , open circuit and short circuit mostly . Common faults are mostly poor contact .
2 . Electrolytic capacitor is very important, when the capacitor leakage will cause the compressor does not start or stop the frequent failure to open . Figure 2 can be determined by measuring the voltage or { 47 } , { 48 } feet voltage Figure 3 A, B in the circuit point to determine whether the normal temperature maintenance .
Fourth, the output control circuit
The output circuit to drive the relay coil by the IC202, IC203, power driver module chip instruction , by controlling the closing and opening of the relay , to achieve the compressors, wind and other motor control .
Now focuses on the fan motor control circuit ( see Figure 4 ) .
When { 1} foot ( ie R252 left ) is low , MOC3020 conductive , SCR trigger , so that the indoor fan operation , but also through a computer chip { 37 } feet carry the fan speed correction .
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