So bought that driver (good deal) along with the "sensor cables" for my project. Which two wires are the ones that are going to power once the FET is activated? Also, does an LED light up when the FET is activated? I wasnt sure if I was seeing things.
Also, the power regulator on the Arduino gets really hot, Im assuming from dropping down the 12V input. Is this something I should worry about?
Take a look at some info about this 4-FET driver board: http://arduino-info.wikispaces.com/Brick-4ChannelPowerFetSwitch
I need to add example of an inductive load like yours..
Make SURE you do have the reverse diode across the solenoid coils like you showed in the first diagram. I don't think the capacitor is needed and may be a potential problem with spike current. You will see a photo that shows the + and - 12V connections. The loads (Solenoids) go from (+) to the S1 thru S4 terminals. I would strongly suggest that you get the whole thing wired up with small 12V lamps as the loads and make sure it all works... You can just use the BLINK program to test and change the pin number(s).. And Yes, there is an LED for each channel on that board that lights up when active.
Regulator Hot?? Hmmm. what other 5V loads do you have on the Arduino? Usually does not get hot with only Arduino running... Check this out....
Keep us posted.. other people need to stuff like this for plant growing etc..
Can you point to a reference on the valves you are using??