Microcontroller Based Electronic Thermostat Project


Electronic Thermostat

Mechanical thermostat has been around for a long time and has been used in industrial control, home appliances control and many other devices to measure and control the temperature of a certain processes. The sensor used usually is a bimetallic sensor that is make from two different metals that expand at different rates as they are heated up.



These metal strips are bonded together and when the temperature rises, the strips will bend upward hence making connection to the contact of the circuit so that current can flow through the circuit.

As the temperature cools down, it will go back to its original position and disconnect the current from the circuit. By adjusting the strip and the contact, the temperature can be controlled. Most oven and air conditioners use this type of sensor. The mechanical thermostat is more widely used due to its lower cost compared to electronic type.

The use of electronic thermostat is becoming more popular now as the cost of semiconductor continues to drop with the advancement of better fabrication and packaging processes. Many applications have switched to electronic control as the control of the temperature is more accurate, easier to control the desired temperature using digital technology, more reliable and interfacing with other devices.

This application note from Microchip uses a low cost 6 pin microcontroller in the design of electronic thermostat. The features of PIC10F204 are as shown below. One advantage is that it has the PDIP package which makes it easier for electronic hobbyists to do their own soldering.

  • 256 Words Program Memory and 16 bytes Static RAM
  • Wide Operating Voltage from 2.0V to 5.5V DC
  • 3 I/O
  • 1 comparator
  • 25 mA source/sink current I/O
  • 1 8-bit timers.


Electronic Thermostat Circuit


Among the learning experiences you can gain from this project are:

  • Power supply is directly tapped from the AC lines voltage using a resistive based power supply. This makes the entirecircuit live and one has to be careful when implementing this project. Ensure that no parts of the circuit is accessible toany user. Use a plastic enclosure to house the printed circuit board properly.
  • The principles of triac is briefly discussed here. The use of zero crossing detection is useful as many applications use this method in their operations. Among them are light dimmer and motor control applications.
  • Learn how to optimise the program code to make it efficient. Many programmers use long routines to accomplish a certain task when a few lines of codes would be sufficient. This experience needs to be learned as one hands on a project and repeatedly look into the code to make it shorter and efficient.
  • Having learned the code, one can then modify and add temperature sensor to make it a close loop control. Display circuity and user interface can be added to the system by migration to a higher pin count microcontroller.


Back to Electronic Thermostat Home Page





Recent Articles

  1. Electronics Design Contest

    oin electronics design contest and win prizes. Test your hardware and software skills against the best designers from the rest of the world.

    Read More

  2. Electronics Events

    Join the electronics events to enhance your knowledge and network with other professionals in this industry.

    Read More

  3. Engineering Free Magazine

    Some engineering free magazine available for you to subscribe today

    Read More

New! Comments

Have your say about what you just read! Leave us a comment in the box below.


Digital Dice 
Project

Explore the use of 7-Segment Display, 555 Timer, Decade Counter and Binary Adder. Get the circuit.

Battery Tester 
Project

Design and build a battery tester to test dry cell and rechargeable battery with a voltage of less than 2V. Check here


Door Bell

Construct this simple door bell chime and have fun. Find out more here



Electronic Kits

If you are looking for electronic kits, electronic gadgets or robotic kits, get them here


Home Alarm 
Project

Build this simple home alarm to protect your house from intruders. See the schematic circuit