Midea 22031020000124, Service Manual

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Service Manual , 2016-12
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compressor, ice maker and defrost heater. The DC 12V power will output stable 5V electricity
after passing through the adjustor 7805, to power for the main control chip and thus monitor the
temperature changes in refrigerator.
10.2 Door trip test circuit(None)
10.3 Temperature test circuit
Its conducted by the sensor, making use of the characteristics that resistance value reduces as the
temperature increases, and the thermistor that has temperature coefficient of resistance in medium
temperature.
The characteristic that resistance value reduces as the temperature increases is deemed to have
negative slope or negative temperature coefficient (NTC), and such thermistor is called as NTC
thermistor. The resistance value changes sensitively with temperature and typically changes 7% ~
3% per degree centigrade. Sensor used in the refrigerator is NTC thermistor.
There is following computing formula for the sensor:Sampling voltage / reference
voltage = R1 / (RNTC + R1)
AD value / reference AD value = R1 / (RNTC + R1)
The reference voltage is 5V, RNTC is the resistance value of the sensor, R1 is R31\R32\R33 in
schematic diagram that is 5.1K