Arduino: A Technical Reference

Chapter 12. Project: Smart Thermostat

You may have heard of so-called “smart” thermostats (I suspect that many people have at least seen the advertisements for them). These devices are a type of programmable digital temperature controller. You might even have one installed in your house or apartment. Some allow you to change settings using Bluetooth or some other wireless connection method, along with an associated app for a smartphone or tablet. Others offer data collection capabilities with wireless download, which can be useful if you want to find out when you are using the most energy to heat or cool your home. There are also, of course, some that don’t do much more than what the old-style bimetallic coil types did, except that an LCD display is used instead of a dial and some switches.

Warning

Disclaimer: If you elect to build and use the thermostat described in this chapter, you do so at your own risk. While it utilizes low-voltage circuits with minimal shock hazard, there is still the risk of damage to your heating or cooling equipment from excessive power cycling or temperature settings that exceed the safe limits of the equipment (most systems have built-in safeguards, however). Use only the low-voltage control circuit for your heating and cooling equipment. DO NOT CONNECT YOUR CUSTOM THERMOSTAT TO HIGH-VOLTAGE (110V AC or greater) CIRCUITS. This includes evaporative coolers and electric heaters.

Background

There are multiple ways to improve on a classic bimetallic ...