Circuit operation principle analysis, electronic device ventilation and heat dissipation automatic control circuit is composed of 555 circuit, here, NE555 is connected to Schmidt working mode. The thermistor RT acts as a temperature sensor, which is connected in series with the adjustment potentiometer RP and connects their voltage dividers to the signal input of the Schmitt circuit. A control relay K is connected between the output of the Schmitt circuit and the power source, and a small ventilation fan that is ventilated and ventilated is controlled by the relay. When the temperature exceeds a certain limit, the control circuit will start to open the ventilation fan to achieve ventilation and cooling. The control process of the circuit is as follows: The thermistor RT is a negative temperature coefficient thermistor, when the temperature rises, its resistance will decrease; otherwise, the resistance will increase. At normal temperatures, the resistance of RT is higher. Through the voltage division of RT and RP, the input of the Schmitt circuit exhibits a low level. This low level is applied to the input of the circuit, and the circuit outputs a high level through the 2 pin. At this time, the transistor VT is turned off, and the relay K is released.
When the operating temperature of the device exceeds the set maximum limit temperature, the resistance of the RT is reduced to a certain value, and the voltage applied to the input of the Schmitt circuit is increased by the partial pressure with the RP. At this time, the circuit is flipped by the 5 pin, the output terminal outputs a low level, the transistor VT is turned on, the relay is energized, the working power of the heat dissipation fan is turned on, and the ventilation fan starts to work, so that the temperature of the device is lowered. After the electronic device ventilation and heat dissipation automatic control circuit is composed, it needs to be adjusted before it can be put into normal use. Before the circuit is adjusted, it is first necessary to set the maximum allowable operating temperature of the circuit. When adjusting, it is necessary to adjust according to this temperature. Assume that the maximum allowable operating temperature of the circuit is 120C. When adjusting, first place the RT in a temperature environment of 120C, and then adjust it after stabilization. Before adjusting, adjust the RP to the maximum resistance. When the thermistor is stable for 120C, adjust the RP to make the NE555 output low. At this time, VT is turned on, relay K is energized, and the heat-dissipating fan starts to operate, and the circuit is adjusted.
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