The temperature controller is an electrical switchgear that controls the temperature of an air-conditioned room. The temperature range in the air-conditioned room controlled by the temperature controller is generally 18°C--28°C. The temperature controller commonly used in window air conditioners uses the principle of pressure to push the contacts on and off. Its structure consists of bellows, temperature sensing bag (test tube), eccentric wheel, micro switch, etc., which is composed of a sealed induction system and a system for transmitting signal power.
There are generally two types of control methods; One is controlled by the temperature change of the cooled object, and the vapor pressure temperature controller is mostly used, and the other is controlled by the temperature difference change of the cooled object, and the electronic temperature controller is mostly used. Thermostats are divided into:
The mechanical type is divided into: vapor pressure thermostat, liquid expansion thermostat, gas adsorption thermostat, and metal expansion thermostat.
Among them, the vapor pressure thermostat is divided into: inflatable type, liquid-gas mixed type and liquid-filled type. Household air conditioners are mainly based on this type of thermostat.
Electronic types are divided into: resistance thermostats and thermocouple thermostats.
The role of the circuit system
The function of the air conditioner circuit system is to control the normal and multi-functional operation of the air conditioner and protect the normal operation of the compressor and fan motor. The main components of the circuit system are: temperature controller, thermal protector, main control switch, running capacitor, and running capacitor of fan motor are fixed in the control box. The picture on the left shows the electrical wiring diagram of a single-chilled air conditioner. The role of the temperature controller is simply to control the start and stop of the compressor.
How it works
Vapor pressure type
The action of the bellows acts on the spring, the elastic force of the spring is controlled by the knob on the control board, and the capillary is placed at the air inlet of the indoor air conditioner to inhale air and react to the temperature of the indoor circulating return air. When the room temperature rises to the set temperature, the thermostat gas in the capillary tube and the bellows expands, so that the bellows elongates and overcomes the elastic force of the spring to connect the switch contacts, at this time the compressor runs and the system is refrigerated, until the room temperature drops to the set temperature, the thermostat gas shrinks, the bellows shrinks and the spring acts together, the switch is placed in the disconnected position, and the motor circuit of the compressor is cut off. In this way, the action is repeated to achieve the purpose of controlling the temperature of the room.
Electronic temperature controller
The electronic temperature controller (resistive type) is measured by the method of resistance temperature sensing, and generally uses platinum wire, copper wire, tungsten wire and semiconductor (thermistor, etc.) as the temperature measurement resistor, and these resistors have their own advantages and points. Most of the sensors in household air conditioners are thermistors.
The thermistor thermostat is made according to the Wheatstone bridge principle, and (left) is the Wheatstone bridge. According to Kirchhoff's law, when the resistance of the bridge R1×R4=R2×R3, the potential of A and C is equal, there is no current flowing between the output A and C, and the impedance R1 of the thermistor changes with the rise or fall of the surrounding temperature, so that the balance is destroyed, and there is an output current between AC. Therefore, when composing a thermostat, the temperature regulation range and operating temperature can be easily changed by selecting the appropriate thermistor.
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