My Raspberry Pi Pool Timer — Why

(There will be more parts.)


Here’s my problem: The filter and the sweep of my pool need to be run every day for a few hours. The corresponding pumps are controlled by two electromechanical timers, one of which failed recently after probably more than 20 years of service. (Timer shown to the right.)


Turns out that this timer is not being manufactured any more. What’s worse is that the panel (next picture) has two cutouts made for this kind of timer, but I am unable to find a replacement timer that would fit into those cutouts or the underlying mounting braces.

So what to do? It’s clear that I don’t really want to hire a “professional” to replace the timers (and probably the entire box), and then install timers just like the old ones. They have too many issues that are hard to stomach in the age of the iPad. It’s 2012 after all and not the 1960′s.

What about controlling the pumps by software? That would have many advantages:

  • instead of having to go out in the backyard, I would be able to see and change the schedule from any web browser.
  • no more loose jumpers, which in the past have caused the pumps to sometimes keep running endlessly or not starting at all.
  • instead of having to change the duration for which the pumps run every day for different seasons (warm weather requires much more filtering because of algae growth), software could automatically adjust the duration based on the date. I might even be able to drive the algorithm by the local weather forecast obtained off the net.
  • PG&E, our local utility, is getting into dynamic pricing. In the longer term, one could automatically schedule the pumps when prices are low. The pool pumps are in the 1/2 to 1 hp range, running for hours every day. They are among of the largest electricity consumers in our house, so it’s worth paying attention to when and for how long they run.

The outlines of the project are quickly becoming clear:

  • I’ll remove both electromechanical timers and replace them with two relays, driven by some kind of microcontroller that connects to our home WiFi network.
  • The electronics go into a small box, which then goes into the controller box.
  • The faceplate of the control box gets replaced with something custom.
  • I probably have to hack some software to run it all.

Read more on selecting the parts