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Micro-Temperature Control Switch Life Tester System Circuit Design

Article Source:Thermal protectorAuthor:YaxunPopularity:Published time:2019-05-25 15:07

The miniature temperature control switch mainly uses a dish-shaped bimetal as a temperature sensing component. The working principle of the miniature temperature control switch is: When the temperature rises, the disc will deform accordingly. When the temperature reaches a value at which the disk is deformed, the jump of the disk depends on the mechanical transmission of the other device, causing the contact to act quickly to turn the current on or off. Operating temperature range: 30 ° C -300 ° C.

The micro temperature control switch is prone to three problems:
First, when the temperature of the bimetal disc of the temperature control switch itself jumps too high. The steam of the electric kettle can not make the bimetal disc reach the jumping temperature, so that the temperature control switch can not cut off the current, and the water of the electric kettle is boiling and cannot be stopped to cause danger; Secondly, the bimetal is a mechanically processed part. Jumping and resetting have mechanical life. Material problems or processing problems have a direct impact on the life of the bimetal. Assume that a kettle is used normally for 5 times a day, and nearly 2,000 times a year. To ensure that the kettle is used for more than 5 years, it is necessary to ensure that the temperature control switch or bimetal has a life of more than 10,000 times; Finally, the small spring of the temperature control switch is the same as the bimetal, and it is also a mechanical processing accessory. Its life also directly affects the life of the temperature control switch and even the electric kettle. Therefore, research and design of the temperature control switch life tester is essentially a life tester for testing bimetal and jump small springs. In the actual production test, the test is selected by sampling.

Circuit board design:
This part takes the microcontroller (MCU) as the core of intelligent control. The temperature of the kettle is collected and measured by DS18B20 temperature sensor, which is transmitted to MCU for processing and displayed in LED or digital tube. When the test encounters a fault or the test is completed, an appropriate sound and light indication is issued.
The circuit schematic is shown in Figure 4.

Circuit diagram of temperature control switch tester
Figure 4. Circuit diagram of temperature control switch tester