PFI Pin Trigger for a Solenoid Valve

[M^2]

I am currently trying to trigger a solenoid valve based on an analog input (level=5 and slope=falling). I need to do this as fast as possible (5 micro-s delay at most). I talked to some people at NI and they recommended using a reference trigger and routing the signal to a PFI pin. I attempted this but it is triggering on the rising edge even though I clearly stated falling edge in the code of the program. I am confused. The code seems like it should work, however it does not. I would appreciate any help.

Thanks,

M^2

[falkpl]

Make sure that the analog signal and ground are hooked up right otherwise you ntrigger will also reverse, that is the rising edge will look like a falling edge on the differential input. 

[Matthew_W]

 Hi M^2,

 The DAQmx Export Signal.vi you have in there is routing a Reference Trigger event to the PFI9 line. I'm not sure this is what you are wanting to do.

Your application sounds like the following:
  1. Acquire a analog input when a trigger condition is met. This trigger condition is a falling edge of the analog input signal.

The VI you attached should work, I made a slight change to the source of the trigger condition and removed the DAQmx Export Signal. The analog signal to be monitored should be wired to pin 20, the source is "/Dev1/APFI0". Where Dev1 is whatever name your daq card is known by to MAX.

 I hope this helps! Please consider the suggestion made by falkpl as well, that would definetly cause the trigger slope to be exactly reversed.

 Best regards,

MatthewW
Applications Engineer
National Instruments
 

[johnsold]

What kind of solenoid valve are you using which can respond in microseconds? All the valves I have seen require tens of milliseconds or more to operate.

Lynn

[M^2]

Right now I am recording an analog signal. The valve will turn on as soon as the program runs (5V). However, when the analog signal is at level=5 and slope=falling edge I want to turn the valve off. I am aware the valve will take time to shut off but I would like the trigger itself to be as precise as possible. As in when the slope turns falling edge while the level is 5 the trigger will occur and send a signal out in at most a 5 micro-second delay.