Relay Stuck ON when program exited or crashed

[Clueless1]

Hi

So I got my USB-6211 turning on and off a relay that controls a valve.  It works great, but I have one last problem.  I would like for the valve to shut off (I/O line = false) should the program loose contact with the USB-6211.  Right now, it seems that it stays in whatever state it was in when the program is improperly exited, has crashed or whatever.  Is there a way to be sure that my tank won't overfill if the program goes south?

Thanks

[johnsold]

I doubt that any DAQ device will do that directly. You need a hardware-based Watchdog Timer. Some NI Digital Output devices have watchdog functions built-in. However, a quick glance at the USB-6211 specifications indicates that it is not one of them.

Lynn

[AnalogKid2DigitalMan]

What Mr. Lynn suggested is the ideal solution. However, would it be possible to add a level float with a switch to your tank that can open the circuit to the valve. Thus when the level is reached, the flow is automatically stopped regardless of the state of the program or digital output.

[Clueless1]

Well sure I could hookup another float to do that.  In fact that is what I'm doing.  I'm reading a water level with a float and using the DAQ to close a realay that operates a valve add more water when it's needed.  But then, what's the purpose of using the DAQ?  Belt and suspenders I suppose.