This little box could help you save on your electric bill. Similar to many smart thermostats like Nest and Honeywell Lyric, this smart device helps you control how you use electricity for heat. In this case, it is not how you heat your house but rather how you heat the water in your hot tub.
The math is quite obvious. While connecting devices to the Internet might seem to increase the total demand for power, this is rapidly offset by using electricity more efficiently. For example, this little box consumes less than a Watt of power while preventing a 10kW heater from running on cold nights or when the spa is not in use for long periods.
If saving the planet is not enough, being able to remotely monitor the status of the hot tub away from home and the convenience of remotely setting the temperature without going outside might convince you to use one.
Building on top of what I discovered in The Cal Spa Connector and The Internet of Spas, I decided to actually build that box.
My setup uses an Atmel ATtiny and an ESP8266. M2M is handled by the ESP using MDNS to discover a local MQTT broker running on the Raspberry Pi. The box subscribes to a command topic to receive temperature change requests and it publishes the hot tub status every minute. I'm bridging my local MQTT broker to Thingspeak so I have a visual representation of the data.
In small batches, you can expect to pay around 25$ to build something similar:
|Resistors, Capacitors, Wires||5$|
The code and circuit example for the AVR portion are available on GitHub. While I am not using an Arduino for the project, it should run correctly with many boards. The sketch will provide you with an I2C interface to the Balboa controller. You will need to interface the I2C with something useful, probably a radio.
Convenience, offsite monitoring and saving electricity, isn't it what IoT is all about?