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Homemade temperature generator (circuit diagram and steps)

Keywords: temperature sensor circuit

The temperature generator is powered by a miner's lamp battery, and the principle that the NTC thermistor is reduced in temperature due to temperature rise and the heating drive current is reduced by feedback, thereby achieving the purpose of constant temperature. Produces 80C temperature, which can be used to verify the temperature protection sensor of the coal mine belt conveyor.

First, the working principle
The device is manufactured according to the principle of lC×UC according to the high-power triode working heat. As shown below. The high power transistor 3DD15 is a heating element, the resistors R2, R3, R4, and R5 are used for temperature control, the light emitting diode D1 is used for power supply indication, and the D2 is used for predetermined temperature illumination indication. The NTC negative temperature coefficient thermistor R3 is mounted on the surface of the 3DD15 metal case to monitor temperature changes. The 3DD15 metal casing surface is also fixed with an aluminum tube with a diameter of 1cm and a length of 5cm for placing the temperature sensor probe to be tested. After the work, as the temperature increases, the resistance of R3 gradually becomes smaller, and the pressure difference between a and b increases gradually. When the D2 turn-on voltage is reached, the illumination indicates that the set temperature has reached (about Smin), and the temperature sensor can be verified. At this time, the surface of the 3DD15 metal case is about 70 °C. When the power is just working, the current is about 3A. As the temperature rises, the voltage at point b increases, and the conduction degree of Tl and T2 decreases, and then the current decreases. When the temperature reaches about 80C, the temperature no longer rises and is maintained, and the current is about 1.5A. The advantage of this device is that it does not need to be connected to the power supply on site, but it is powered by the miner's own battery (7Ah/4.2V), which can be removed by screwing off the miner's lamp, which is convenient and explosion-proof.
NTC negative temperature coefficient thermistor applied to temperature generator

Second, the production method
A 3cm×4cm copper clad plate was trimmed by knife engraving. After the engraving, the CCL was polished with fine sandpaper, and the component mounting holes were made with a micro electric drill and the alcohol rosin solution was applied. Dl is an ordinary green luminous tube; For clear indication, D2 uses high-brightness red LEDs; 3DD15 is a metal shell package; NTC resistor R3 is 2.5K at normal temperature, reaching a predetermined temperature of about 350Ω; The other resistor is a 1/4W metal film resistor. This circuit can be basically installed and calibrated with a mercury thermometer. Simply adjust the resistor R4. After the circuit board is finished, it is installed in the small junction box, and the aluminum tube and the light-emitting tube are protruded from the wall of the box, and the gap between the aluminum tube and the box body is sealed with epoxy resin. The objects are shown in the figure below.

Third, the use of effects
The purpose of verifying the temperature is achieved through field trials, highlighting the characteristics of portability, explosion-proof and temperature stability. It reduces the labor intensity of maintenance personnel and solves the problem that it is impossible to verify the temperature sensor on site in the long run. The temperature sensor is sensitive and reliable, and the belt conveyor is safely operated, and the economic benefit is obvious.
Temperature protection sensor of coal mine belt conveyor

Temperature sensor guarantees safe operation of the belt conveyor
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