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Making a Simplest Room Thermometer

This circuit can be considered as a fun project but once you have built it, you will find the unit serving some very useful purposes.

In the previous post we learned some of the features of the outstanding temperature sensor chip LM35, which gives outputs in varying voltages that's directly equivalent to ambient temperature changes, in Celsius.

This feature in particular makes the construction of the proposed room temperature thermometer circuit very simple.

Using a Single IC LM35 for the Design

It just requires a single  IC to be connected with a suitable moving coil type of meter, and you start getting the readings almost immediately.

The IC LM35 will show you a 10mv rise in its output volts in response to every degree rise in the temperature of the atmosphere surrounding it.

The circuit diagram shown below explains it all, no need of any complicated circuitry, just connect a 0-1 V FSD moving coil meter across the relevant pins of the IC, set the pot appropriately, and you are ready with your room temperature sensor circuit.

Setting up the unit

After you have assembled the circuit and finished doing the shown connections, you may proceed with the setting of the thermometer as explained below:

  1. Put the preset in the midway range.

  2. Switch ON the power to the circuit.

  3. Take a bowl of melting ice and immerse the IC inside the ice.

  4. Now carefully start adjusting the preset, such that the meter reads a zero volts.

  5. The setting up procedure of the room thermometer is done.

Once you remove the sensor from the ice, within seconds it will start displaying the present room temperature over the meter directly in Celsius.

Need Help? Please leave a comment, I'll get back soon with a reply!


  1. I like them circuits SWAGATAM,

  2. Hi Swagatam !!!
    I can't see any thermistor
    how the ic will sense rise in temperature

  3. Hi Asif, the LM35 itself a temperature sensor, we don't need a thermistor here

  4. Hlw.. I NeeD ur help. to make a 12V 10A DC Fan speed controlr? to make room temperature meter?

  5. you can try the following:

  6. how do I add a 7 segment display to the circuit for both negative and positive temperature display?

  7. you can integrate the following circuit with the above for getting a digital readout


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