Simple automatic controller

Simple automatic controller
Here is a simple diagram for automatically turning on the fan and controlling its speed depending on the sensor temperature. This simplest scheme, consisting of just two elements, can be applied in its amplifiers, power supplies, computers, etc.
Simple automatic controller

Operation of the automatic controller circuit

The LM35 is used as a temperature sensor. It looks like a three-legged transistor. The output voltage of this sensor is linearly proportional to the temperature of degrees Celsius. That is - 10 mV / degree Celsius, for example, if the temperature is 45 degrees, then the voltage at the sensor output will be 450 mV or 0.45 V. The base of the transistor BC548 NPN structure is connected to the sensor output. From the characteristics of this transistor it is known that it starts to open then,when the voltage between the base and the emitter exceeds 0.4 V. Therefore, the fan starts to rotate when the temperature of the sensor exceeds 40 degrees. And when the sensor temperature exceeds 60 degrees and the output voltage of 0.6 V appears, the transistor will open fully and the fan will rotate to full capacity.
Simple automatic regulator
This is such a simple operation and such a simple circuit. If the circuit is unstable or intermittent, I recommend connecting a 0.01 µF capacitor directly to the LM35 sensor supply legs Instead of a computer cooler, you can turn on a brush motor of low power, but then you must consistently enter a resistor with a resistance of 10-50 Ohms in series with it.

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