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Digital Temperature Sensor

Sensors make working with any project fun and simple to do, there exists thousands of sensors and we get the choice to choose the right sensor for our projects or needs. But nothing is better than designing your own DIY sensors to work with a wide range of micro-controllers so you have the exact design you need for your project.

This instructable will be a part of a series of instructables in which I show you how to build sensors compatible with most microcontroller you can find. In this instructable I'm going to show you How to to design your own Temperature sensor, which would use a waterproof Resistance temperature detector and the LM358 IC.

Step 1: Components

Here is a list of what you will need to get started with instructable,

  • LM358 IC
  • Resistance Temperature Detector
  • 10K Pot
  • LED
  • 330 ohm resistor
  • 10K resitor
  • PCB (Optional)
  • Connecting Wires
  • 5v Power Supply
  • Breadboard
  • Multimeter (Optional)

Step 2: Circuit

The circuit is based on LM358 IC which is an OP-AMP with an operating voltage range of 3v to 32v which is suitable to work with most micro-controllers of logic level 5V or 3.3V. The temperature detector is connected to the non inverting terminal of the op-amp and each time the temperature raises above certain value the the circuit detects the change and turns the LED on giving a High pulse.

Signal can be fed to the microcontroller via the Pin 1 of the LM358 IC.

Step 3: Temperature Detector

The temperature sensor I used is a resistance temperature detector, it has a high temperature range and is water proof you can get this temperature sensor for cheap on eBay.

The resistance changes linearly with the change in temperature and the LM358 is used as a comparator and detects the change in resistance and turns on the LED when certain threshold temperature is reached.

Step 4: Sensitivity Calibration

The sensitivity of the circuit can be changed by varying the 10K pot, varying the pot will change the threshold temperature to a different value.

Step 5: Going Further

After you have tried it out on a breadboard you could build it on a PCB or as an Arduino shield, for the spring you should use single strand wire. If you would like me to write a code for your microcontroller feel free to PM me.

In the next instructable I will show you how to build a pressure sensor.



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