My equipment is pretty old and the paragon timer I have has no trippers. The intermatic trippers are incompatible not to mention I read that the mechanical timers are pretty wasteful. I am planning to do a control system for it. This is my thought thus far.
Nema 4 enclsoure
Linksys NSLU2 with custom linux system on it
3 contactors - 1 for pump, 1 for light, 1 for future peristalic pump (these would live in the current electrical box in place of the timer)
USB relay board (either DIY or buy one of the stupidly expensive ones already made)
USB io board (thinking the fusion board - typically used in automotive, but I already have another one)
2 temperature senders ( 1 tapped into the pvc for pool temp, the other dangling for air temp )
2 pressure senders ( 0-150 psi dakota digital )
The general idea is that with this kit I would be able to start up and shut down the pool pump/light based on any schedule. I would be able to then add controls into my home control panel so that I can turn on/off pool equipment from the living room touch panel. I would be able to write a small monitoring program that would make sure suction and pressure side numbers seem right and if not shut the system down and send me a text message. This would prevent the pump from running dry for very long because when it does the pressure side pressure goes to nothing. Suciton side vacuum would also go to nothing. I was originally going to interface with jandy valve actuators but they are expensive and now that I've solved my system leaks I don't have to manipulate the valves to successfully start the system.
Alternatives may be had for the NSLU2 - I could probably use a USB extender and just bury a CAT5 cable and conduit into my server in the house.
Additionally the pressure sender is for the car. Any industrial pressure sensors seem to be on the costly side ($100+) and this automotive air pressure sender is only $20 or so. I was thinking I'd just attach a long 1/4 or 1/8 tube between the sender and the pvc and probably water would never get to the sender. They also sell an oil pressure sender. I'd think oil gases are pretty bad so maybe it can handle the chlorinated water.
The temperature senders are for automotive coolant/oil. I've found that they are metal and they don't really indicate what kind of metal they are made from. I wouldn't want it to corrode and add metals to the pool water. They look almost like a really high grade bolt.
I have two main goals with this setup - inexpensive and reliable. The inexpensive part is important. I can't be spending $200 each for a pressure sensor. I need cheap <$20 sensors. Cost target of $300 is what I am looking for. The software is no problem for me at all - my main questions are what would you guys in the know do for sensors and relay/io boards.