Digital Temperature Sensor

Sensors make working with any project fun and simple to do, there exist 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 the most microcontroller you can find. In this instructable, I'm going to show you How to design your own Temperature sensor, which would use a waterproof Resistance temperature detector and the LM358 IC.

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 Resistor
• PCB (Optional)
• Connecting Wires
• 5v Power Supply
• Breadboard
• Multimeter (Optional)

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 rises above a certain value the circuit detects the change and turns the LED on giving a High pulse.

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

The temperature sensor I used is a resistance temperature detector, it has a high-temperature range and is waterproof 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 the certain threshold temperature is reached.

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.

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

If you have any queries, feel free to leave a comment below or PM me and I would try to help you.