The thermistor RT is connected to the input of U1A. It adjusts the voltage divider with resistors R2 and RP to make the input voltage of UIA high and the output voltage low. When the temperature exceeds the set temperature limit, because the resistance of RT becomes smaller, the voltage at the U1A input terminal is low through the voltage dividing circuit, and the output is high after being inverted. On the one hand, this high level is added to the 8-pin of the control end of the multivibrator composed of U1C, U1D and the RC circuit. The base of transistor VT1 is added to make it conductive, and the relay is energized to attract; on the other hand, after the U1B inverting output is low, the light-emitting diode LED emits light.
Power supply voltage: DC 4.5-5.0V Board size: 32 * 72mm
The over-temperature monitoring automatic control circuit is composed of four 2-input NAND gate digital integrated circuit CD4011 and a thermistor RT to form a measurement and control circuit and a siren sound generating circuit. The relay K is used as the execution circuit. The thermistor RT acts as a temperature sensor. When the temperature exceeds the set temperature, the relay K is driven by the transistor VTI. Can be used for over temperature monitoring alarm, normally open and normally closed contacts of relays can drive a variety of controlled equipment and more.
1 x Temperature Over Temperature Monitoring Detection Control Kit