Safe Shutdown of cRIO when Removing Power

[JimMacD]

I'm wondering how to manage the safe shutdown of a cRIO application on a portable unit where the user will be removing power (probably via an physical power switch) during normal operation. Normally, I would design an application with a Initialize_Running_Shutdown state machine, where the shutdown is initiated by the HMI sending a shutdown command, but this will not be the case here.

On a side note, I've also be wondering how to deal with this during extended power outages (once UPS power runs out, the control system dies).

How can we ensure that when power is removed, the cRIO sends the application into the proper shutdown routine?

Any input would be appreciated. Thanks

[RavensFan]

If the power supply had a serial port for communicating to the PC its status, and teh cRIO has a serial port, you could put in a routine that communicates with the UPS.  Upon getting a message that it is on battery power, then go through your shutdown routine.

Another alternative is to use a 120V relay powered by the line side of the power supply.  Use the contacts as part of a digital input on the cRIO.  Monitor the digital input and start a shutdown routine if you detect the relay has opened.

One thing I've noticed is that UPS's will periodically go onto battery power for a few seconds.  It seems to be daily.  So you may want the routine to only initiate the shutdown routine if it has detected the power has been off for some minimum period of time.

[viScience]

In my case I read the UPS status and display a warning on my HMI's when on battery backup.  When the UPS status indicates < 50% power left, I  go into a shutdown state.

[JimMacD]

I was thinking it would involve monitoring either UPS or Line status directly. I've been spec'ing out a new type of UPS for my control systems (the one I had been using had no communications options) with a relay output card option for 24V logic.

What got me thinking about this was working on an OLD Allen Bradley PLC5 recently. It was all ladder-logic, and just had a power ON/OFF switch. Very low tech. I wanted to see if perhaps the lower-end PLCs aren't as sensitive to just loosing power as the cRIO might be, simply because the application is much simpler.

[JimMacD]

This document has a number of points for this topic:

Designing High Availability Systems with CompactRIO and Compact FieldPoint

http://zone.ni.com/devzone/cda/tut/p/id/6546