NI 9263 ungrounded signal

[JR3]

Hi,

We are planning to use NI 9263 Analog Voltage outpur module to control a DC motor. We are using a DART motor controller for it.  It says that for the voltage follower, the voltage input must not be grounded. We already tried it once and pretty much mess up the controller. Is there a way that we could actually output an ungrounded signal in the NI 9263?

Thanks

JR

[Mark_SAI]

Have you got a link to the datasheet of the DART motor controller in question, so I can investigate further?

[JR3]

Hey macaba,

Here is the link for the Dart motor controller

http://www.dartcontrols.com/manuals/250GManual.pdf

It is in pg 5, Terminal strip wiring.  We only have the basic controller without the optional control modifications.

Thanks

Message Edited by JR3 on 07-22-2009 10:26 AM

[jschwartz]

Hi JR3,

You have to reference your signal to something.  From the datasheet, it sounds like you can reference it to the -ARM or speedpot LO whether or not the MIN trimpot is active.

[Mark_SAI]

Jim is referring to the following quote:

Electronic speed input (voltage follower) may be referenced to speedpot LO if the MIN trimpot
adjustments are to be active. Otherwise, inputs may be referenced to -ARM, which will bypass the MIN trimpot.
NOTE: INPUT MUST NOT BE GROUNDED!!

The only difficulty is that by connecting the common of the 9263 to the speedpot LO, you are effectively grounding that input through the 9263 to ground and therefore may have undesirable currents and effects. Is this what you have tried?

Thanks

[JR3]

Thanks guys for the reply.

I actually tried connecting the speedpot low to the common of the 9263.  At first it did work, but the following day, when I turned it on, I heard a pop and the motor ran at full speed all the time.  I tried connecting the speed potentiometer back and is still didn't work.  The tech support said I broke it because I put a grounded signal to it.  

I thought that the 9263 COM was actually isolated from earth ground. 

I already have a replacement controller right now operating using the speed potentiometer. Could I again try it? Don't want to blow it up again. 😄

Message Edited by JR3 on 07-22-2009 04:20 PM

[AnalogKid2DigitalMan]

Here is a +/-10V in to out voltage isolation module example, one of many from various manufacturers. Note that there is filterin on some units which may slow down the response time.

http://www.dataforth.com/model.view.aspx?modelid=53

-AK2DM

[Mark_SAI]

Hello!

AK2DM has a good solution, it would be best not connect up the motor controller to the 9263 analog output module directly, use isolation. There are no C-series modules as far as I can see that offer analog output isolation signal conditioning, there are other products that do (SCC-AO10 and SCXI-1124) which I mention as chances are, you may have these in storage somewhere!

To clarify, if you connect the motor driver to the 9263 module directly, you will blow it up again!

[JR3]

Thanks AK2DM and Macaba,

I tried looking here in our lab and found this lying around,

http://www.dataforth.com/device.view.aspx?deviceid=1187

http://www.dataforth.com/catalog/pdf/scm5b49.pdf

Would this work? I just need to figure out the 14 pins here

Thanks a lot 

[jschwartz]

It looks like those modules would provide isolation.