So, been playing with this Claber Oasis thingy for a couple weeks on and off; pretty well got it hacked for anyone interested.

It's a drip system -- you put "drippers" in your pots and feed the drippers with the Oasis tank (holds 25 liters). The Oasis has a valve and a timer (runs on a 9 volt battery), but it isn't well suited for pot growing because the timer wants to run twice a day and you can't get enough water for thirsty pot plants. You control the amount of water by the number of drippers you put in each pot and how long the valve is open. Four drippers for an hour will deliver about a liter of water. Four drippers seems about the "reasonable max" for me in one 3-gallon pot, and I've been watering almost a gallon per pot, every 4 days or so. You want the wet-dry cycle and the timer that comes with the Oasis can't do it.

Turns out, the Oasis timer is based on a PIC microcontroller, so the odds are good one could reprogram it to get what you want, but that would take some reverse engineering of the electronics and I didn't have the time or inclination for that. But, I did figure out how the valve works. Apply 9 volts and it opens. Apply 9 volts with the polarity reversed and it closes. Based on that, I threw together a little Arduino - based controller to run the valve and now have a set up that will deliver 3 liters every 4 days to each of my two plants. Arduino Uno was $15 from a Chinese Amazon dealer, $7 or so for a relay board to control the valve; misc wiring and stuff, I'm in it for about 30 bucks, and probably not much more than 2-3 hours of my time.

For the time being, I've decided not to run my liquid plant food mixture through this because of concerns that it might plug things up. But, I think it'll handle pH adjusted water just fine for a watering or three. imp: