In this Article, I will show you to how to make temperature controlled fan circuit diagram utilizing LM35 Temperature Sensor. This circuit can be utilized to naturally turn ON a switch when the ideal temperature is recognized.

This Temperature Controlled Fan Circuit is a gadget or circuit, which is initiated dependent on the Temperature. Any Temperature Controlled Switch comprises of three sections: Sensor, fundamental control unit and the switch.

How Temperature Controlled Fan Circuit Diagram Works

The picture shown below is a basic Temperature Controlled fan Circuit utilizing LM35 Temperature Sensor, LM358 Op Amp, and a 5V Relay Module.

Let me start describing the design of the Temperature Control Switch circuit with the Op-Amp LM358. Pins 8 and 4 (V+ and GND) of LM358 are connected to +5V and GND.

Since LM358 is a dual op-amp IC, you can use either of the Op Amps. Pins 1, 2, and 3 are associated with one ap amp and pins 5, 6, and 7 with the other. I will be using the first op-amp i.e. pins 1 (OUT), 2 (INA-) and 3 (INA+).

Now, connect the Centre terminal of the 10KΩ Potentiometer to Pin 2 of LM358 (the other terminals of the POT are connected to +5V and GND). Pin 3 of LM358 is connected to the OUT Pin of LM35 Temperature Sensor. The other two pins of the LM35 IC are connected to +5V and GND you can see in diagram.

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Parts List for Temperature Controlled Fan Circuit Diagram

  1. IC LM358 1pc
  2. Temperature Sensor LM35 1pc
  3. Transistor BC547/548, 2n2222 or any NPN Transistor 1pc
  4. Relay 5 Volt DC 1pc
  5. Diode 1N4007 1pc
  6. VR1 10K Pot 1pc
  7. Resistor 1k 1/4watt 1pc

Systematic Temperature Controlled DC Fan

Temperature Controlled Fan circuit

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How Temperature Controlled Switch Circuit Works

The working of this Temperature Controlled Switch circuit is very simple. Let us start with LM358 Op Amp. In this circuit, it is designed as a Comparator for example it looks at the voltage levels at Pins 2 and 3 and produces a relevant Pin 3 (IN+) of the Op Amp is the non-modifying input and is associated with OUT of the LM35 Temperature Sensor. Pin 2 (IN-) on the other hand, which is the inverting input, is connected to a voltage divider i.e. a Potentiometer.

Under normal condition, the inverting input will be greater than the non-inverting input and as a result, the output of the Op Amp is LOW. Since this output is connected to the Relay, it stays turned OFF.

When the temperature increases, the output of the LM35 Temperature Sensor increases as a rate of 10mV/0C. If the temperature reaches a certain threshold, the non-inverting input of the Op Amp becomes higher than that of the non-inverting input and as a result, the output of the Op Amp LM358 becomes HIGH. This in turn will turn ON the relay.

Watch Video :- How To Make Temperature Controlled Fan