In this tutorial i will show you how to make a simple Temperature or Light Sensor Module to control Fan or Light circuit. To make this you can watch the video which is embedded in this step. The video contains details of construction, parts list, circuit diagram & testing or you can continue reading the post for further details.

Step 1: Parts List

Thermister 4.7K
Trimmer 10K
2n2222
Capacitor 10uF/25V
Resistor 33K
Diode 1N4007

Step 2: Circuit Diagram

Construct the circuit on a PCB as shown in the circuit diagram. I am using a fabricated board for my sensor module. To fabricated a PCB yourself, construct the circuit in a software which enables to create the Gerber file. To create the Gerber file i am using KiCad & for the fabricator i am using the website JLCPCB.Com . The board received from the JLCPCB.com is shown in the second image.

Step 3: Block Diagram & Testing

Working

The working of the circuit is very simple
a. With Thermsitor - when the temperature is increased (In my case i am using hot water to increase the temperature) the resistance of the thermistor decreases as a result the current flow increases to a level where the relay is turned on & when the temperature decreases the resistance increases which halts the current flow and in turn deactivates the relay module.

b. With LDR - when the light intensity is increased the resistance of the LDR decreases as a result the current flow increases to a level where the relay is turned on & when the light intensity decreases the resistance increases which halts the current flow and in turn deactivates the relay module.

Other Info

The sensor module can work with voltage range 5 to 12V, But when connected to a relay module the supply voltage should be above 10 volts.

To adjust the sensitivity of the circuit you can use the trimmer.

Testing

To test the circuit with relay module i have showed the block with the pin details & also named the individual modules with the pin name, so please refer while constructing the circuit.

For testing of the circuit you can watch the video attached in the first step or Click Here & for for the testing without the relay module & for the testing on the bread board you can Click Here

Thank You for reading & watching
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