For those times that we go on a holiday or a business trip we needed a solution to keep our plants alive. We initially bought a system online which consisted of one big timer controlled pump with a long hose that would split into numerous small sprinklers for each individual plant. The problem with this system is that it was very difficult to adjust each sprinkler to give the right amount of water for each specific plant. Second problem was reliability, the large pressure differences along the hose would sometimes lead to coupling pieces disconnecting.
We therefore decided to built our own system using Industruino as the main controller.
We took 8 small 5V centrifugal pumps, one pump for each plant. The pumps all suck-in water from the same large bucket but each pump pumps the water to its respective plant. This way by controlling how long each pump is activated we were able to adjust exactly how much water each plant receives. At startup each 5V pump can draw up to 2A, so we needed a way to switch this large current with the small currents that each Atmega pin can provide. We soldered 8 TIP120 darlington transistors inside onto the baseboard of the Industruino, making a nicely integrated product.
Since building the system half a year ago we used it three times and it has already saved us a lot of hassle worrying about the fate of our plants.