interlock trip button within a VI -- but doesnt trip when computer turns on/off

[bradj0]

Hi All-

I want to trip an interlock (e.g. a reed relay or something like that) via a button-press within LabView. However, it is absolutely critical that the interlock is not tripped when the computer turns on or off. I have had problems with DIO and AO ports being 'unknown' during computer ON/OFF and so I am not sure how to proceed. Btw- I have a PXI-6229 card. Ideally I would like to trip up to four independent interlock systems. I was thinking of using the digital waveform generation capability of the 6229 and then a Freq-to-Volt IC. I would send a particular waveform of some frequency to the DIO port, and the F-V converter would actuate the interlock relay. Any other ideas?


thanks-
-brad

[Jeff_T.]

Brad,

If you are using DAQmx 7.4 or later, your m-series card supports programmable power-up states.  If you go into MAX, right click the PXI-6229 and select properties, there will be a tab called "Power-up States."  It is recommended though that you do not change these states often because the EEPROM has a limited number of read and writes.  Have you tried this feature for your application?

Regards,

Jeff Tipps
Applications Engineer

[bradj0]

a) are the power-on states guaranteed ? if the card output spikes and trips the interlock.... that would be really bad

b) how many times can they be changed?

[Jeff_T.]

brad,

The programmable power-up states will definately work but your F-V converter is a good idea as well.  We do not have any specifications on the endurance of the EEPROMS.  I know from personal experience that many EEPROMS have an endurance of around a million so if you are not doing anything else to the EEPROM then it will be difficult for you to manually wear it out.

Jeff

[Jeff_T.]

brad,

I should add that even though the power-up states are rock solid, there is no hardware in place to gaurantee the states of your digital lines during power-down.  You are already considering some external hardware to help eliminated unwated switching and I encourage you to continue with that thinking.

Jeff