Is using two pneumatic valves on one spike legal? How should I connect them?
yes it is legal.
<R48> Each power-regulating device (speed controller or relay module) shall control one and only one electrical load (motor, actuator or compressor).
A. Exception: Multiple low-load, pneumatic solenoid valves may be connected to a single relay module. This would allow one relay module to drive multiple pneumatic actions. No other electrical load can be connected to a relay module used in this manner.
as for connecting them just attach the 2 positive wires to the same spot on the spike and do the same with the negatives.
… actually, you’d need to put +12v and GND on the input side of the spike from your power distribution board, then, on the output side of the spike, you wire up the RED wire from the first solenoid to M+, the RED wire from the other solenoid to M-, and take both of the blacks from both solenoids back to ground.
Drive the spike “forward” and you get one solenoid active, drive it “backward” and you get the other solenoid active.
Also, you don’t technically need to use a spike to control a pneumatic valve. You could just rig up the relay bumper on the cRIO. I’m pretty sure its legal to hook up two solenoids to one connection on the relay bumper, but I’m not positive, so as our team says, RTFM. (Read the FIRST manual)
(And yes, the F in RTFM didn’t always stand for FIRST)
What you are asking is legal but not always desirable. I would suggest you check out the Spike manual on the IFI website http://www.ifirobotics.com/spike.shtml. There is some application notes in the manual that you might find useful.