Just a short post to follow up on the how-to Raspberry Pi post. I went into detail on how to get one going, but I never really said what I was doing with the thing. So, in case anyone is curious:
First I installed all the software I wanted. I set the Pi up as a headless (no monitor, keyboard or mouse) network-controlled computer. I installed a wifi dongle so it became a headless, wireless network-controlled computer.
I set the Pi up to control a relay board, where the relay’s normally closed (when unenergized) contacts normally allow power to feed through an otherwise vanilla extension cord. Into the extension cord, I plugged my salt tank’s active filtration pump. So the Pi is plugged into the wall, and the filter pump’s power is switched by the relay.
Then I wrote a little (very little) thing in Python that lets me activate the relay for a period of time, during which the pumps become disabled.
What this is used for is, first, when I feed the fish and corals, I don’t want the food for the fish and the micro-organisms for the corals pulled into the filter, clogging it sooner than otherwise would occur, and wasting the food. Second, when I clean or change the filters, I don’t want the pump running as it can dump debris from the filter chambers into the tank.
So I kick this, the pumps turn off for about 45 minutes, I feed the waterkids or deal with the filter media, and walk away. 45 minutes later, without my having to worry about it or hang around to see it done, the pump turns back on, and all is good — no fuss, no muss.