How the temperature control switch works

Dongguan Yinyin Hardware Products Co., Ltd. specializes in producing silver contacts, relay contacts, silver alloy contacts, in-mold riveting contact points, punching and riveting integrated contact composite contacts, shaped contacts, solder contacts, environmentally friendly contacts, Switch contacts, rivet contacts, riveting contacts.
Before we got to know what is the temperature control switch, but some people do not know the principle of the temperature control switch, then let's talk about the principle of this temperature control switch.

Vapor pressure type

The action of the bellows acts on the spring. The spring force of the spring is controlled by the knob on the control panel. The capillary is placed at the air inlet of the air in the air conditioner to react to the temperature of the indoor return air. When the room temperature rises to the set temperature, the temperature sensor gas in the capillary tube and the bellows expands, the bellows is extended and the switch contact is turned on against the spring force of the spring. At this time, the compressor is running, the system is cooled, and the temperature is cooled. When it is lowered to the set temperature, the temperature-inducing gas shrinks, the bellows shrinks together with the spring, and the switch is placed in the off position to cut off the motor circuit of the compressor. This is repeated to achieve the purpose of controlling the temperature of the room.


The electronic temperature controller (resistive type) is measured by the method of resistance temperature sensing. Generally, white gold wire, copper wire, tungsten wire and semiconductor (thermistor, etc.) are used as temperature measuring resistors. These resistors have their own advantages and disadvantages. . Sensors for household air conditioners are mostly in thermistor type.

The thermistor thermostat is based on the Wheatstone bridge principle (left) is the Wheatstone bridge. Connect the power supply E to both ends of the BD. According to Kirchhoff's law, when the resistance of the bridge is R1×R4=R2×R3, the potentials of the two points A and C are equal, and no current flows between the output terminals A and C. , the magnitude of the resistance R1 of the thermistor rises or falls with the ambient temperature

The change is changed, the balance is destroyed, and there is an output current between the ACs. Therefore, when the thermostat is constructed, the temperature adjustment range and operating temperature can be easily changed by selecting an appropriate thermistor.

Metal expansion

According to the principle of thermal expansion and contraction of objects. Thermal expansion and contraction are commonalities of objects, but different objects have different degrees of thermal expansion and contraction. The two sides of the double gold piece are conductors of different materials. At different temperatures, the double gold piece is bent due to the different degree of expansion and contraction, and the set contact or switch is touched, so that the set circuit (protection) starts working.

● The working temperature performance is fixed, no need to adjust, simply, reliable operation, no arcing, long service life and less radio interference.

● Electrical parameters

AC250V 5A/10A/16A AC120V 7A

● Temperature working range: -25°C∽+240°C+1°C∽2°C

Can be produced according to user requirements

● Life expectancy of more than 100,000 times

● Insulation value >100MΩ

● High precision, good stability and good synchronization

product structure

The product is a thermostat with a bimetal as a temperature sensing component. When the appliance is working normally, the bimetal is in a free state, the contact is in a closed/open state, and when the temperature reaches the operating temperature, the bimetal is heated. The internal stress acts quickly, opens/closes the contact, cuts off/closes the circuit, and thus controls the temperature. When the appliance cools to the reset temperature, the contacts automatically close/open and return to normal operation.

Widely used in: water dispensers, water heaters, sandwich toasters, dishwashers, dryers, disinfection cabinets, microwave ovens, electric coffee makers, electric cookers, refrigerators, air conditioners, glue machines, office equipment, car seat heaters, etc. Electric heating appliances.

Main use of the product

The thermostat is a small temperature controller with fixed operating temperature performance, no need to adjust, simply, reliable operation, no arcing, long service life and less radio interference. The thermostat is small temperature control and overheat protection; such as disinfection cupboard, electric boiling water bottle, coffee pot, electronic tile support, warm water bag, water dispenser, hair dryer, vacuum cleaner, electric heating stove, microwave oven, electric iron, dry Clothes, motors and other electrical appliances.


It has the characteristics of stable performance, high precision, small size, light weight, high reliability, long life, and low worry on the radio.


1. When using contact temperature sensing, the metal cover should be close to the mounting surface of the controlled appliance. To ensure the temperature sensing effect, the temperature sensitive surface should be coated with thermal grease or other similar heat transfer medium.

2. Do not crush, loosen or deform the top of the cover during installation to avoid affecting performance.

3, can not let the liquid penetrate into the temperature controller, do not crack the shell, do not arbitrarily change the shape of the external terminal.

4. The product should be used in a circuit with a current of no more than 5A. The copper core should be selected from 0. 5-1mm2 wire connection; if it is not used in a circuit with a current of 10A, the copper core should be 0.75-1.5mm2. connection.

5. The product should be stored in a warehouse with a relative humidity of less than 90% and an ambient temperature of 40 ° C below, which is ventilated, clean, dry and free of corrosive gases.

The classification of KSD301 can be classified according to temperature, or by material, or by installation.

According to the nature of the action: can be divided into normally open action, and normally closed action.

According to the material, it can be divided into: electric wood and ceramic body


1 : rated working voltage (250V)

2: rated working current (10A)

3: Starting current (A)

4: Stall current (A)

5: a: Installation method: embedded, external

b: Dipping method: dripping paint, immersion paint, vacuum dipping paint, no dipping paint
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