Depending on where you live, pool season is drawing to a close. On the other hand, if you want to finally implement that Raspberry Pi/Arduino pool control system you’ve been contemplating for the last few years, there’s no better time than now!
Hacker “neilroeth” recently installed his own custom system, not purely out of a desire to make something awesome, but because his pool controller finally decided to bite the dust. Since a replacement would cost around $800, he chose to make his own at a cost of less than $100 instead— using some components that he already had lying around.
The resulting system can run his pool automatically, including a variety of actuators, lights, a heater, and a main pump motor. Everything is now controlled directly by an Arduino Nano and a relay board — along with a relay adapted from the existing system to switch the powerful 240V, 2HP main pump. A Raspberry Pi provides a browser-based user interface and switching logic via a Node-RED routine, which it transmits to the Arduino via a USB serial connection. Air and water temperature data are measured using thermistors connected to the Arduino and fed to the Pi.
The build is well documented, and would make a great reference to review before starting your own project. As with any undertaking involving electricity — especially involving mains power — be sure to take the proper precautions!