Applying voltage to NI9472 output pin - will we damage the device?

[Bandit]

Hi,

We have an application using NI9472 digital output modules on a NI9178 chassis used to drive 24V signals relays that in turn switch higher currents to motors. These are controlled remotely via a LabVIEW application.

We wish to add local control for use while setting our equipment up - at least one motor needs to be finely adjusted locally. To do this we wish to connect a switch in parallel with the NI9427 module. Operating this will take the place of the NI9472 output. Doing so will place 24VDC on the output pin of the NI9472.

My question is, will this damage the NI9472 module?

The spec for the NI9472 module says:

I/O protection

        Voltage.................................30V max

        Reversed voltage...................None

I'm not sure quite sure what the Voltage and Reversed voltage definitions are, and which applies to the scenario I'm describing?

Does the Voltage spec mean applying voltage to an output, or the max voltage it can be expected to deliver?

Does the reverse voltage spec mean applying reverse (-ve) voltage to a pin, applying a negative (reverse) voltage to the Vsupply pin, or applying a voltage to an output expected to source current which could drive current into the output channel (the reverse of it's intended operation)?  

One suggests we will do damage, the other suggests we won't. If we risk damage we will need to implement a protection diode.

I look forward to your advice/clarification.

Regards,

Bandit.

[johnsold]

Why did you not add this additional information to your first thread rather than starting a new one?

I am always very cautious about connecting a two sources together unless they are specifically designed to operate that way. 

My suggestion would be to use a single pole double throw switch to connect the external source to the motor while simultaneously disconnecting the NI 9472.

Lynn

[Bandit]

Lynn,

Thanks for your reply, that's a good suggestion.

Original post? I didn't know there were two. I had some trouble while posting so perhaps that's the source of the double post.  I'll try and track the other down and remove it.

EDIT - I've been unable to find a way to remove the partial post that was made in error, so I have flagged it with a moderator to see if they can.

Bandit.