RS232 to RS422 via GPIB-232CV-A

[sullivnc]

Hello all,

I have a motor controller that needs an RS422 signal.  If it sees a differential voltage above 2.5 V DC, the motor is activated.  If it sees a differential voltage below 2.5 V DC, the motor is deactivated.  I bought an RS232-to-RS422 converter.  With the power on to my GPIB-232CV-A, I get a permanently supplied +5.2 V signal out of my converter.  My suspicion is that if I can get a contsant signal out the the Tx pin on the GPIB-232CV-A (pin 3), then that will supply the negative voltage that I need, and bring the differential voltage down below the threshold.  My question is, using LabVIEW, does anyone know of a way to get the GPIB-232CV-A to supply a constant Tx signal?  Any help would be greatly appreciated.  Thanks.

[Dennis_Knutson]

Sorry, that makes no sense to me. If the controller is truly RS422, then you would be sending a command via a VISA Write and not some constant voltage. If it is not RS422 and does on fact require set voltages, then get a DAQ card with an analog output. The GPIB-RS232 converter seems superfluous.

[sullivnc]

Obviously there are other ways to do it.  I asked about this specific setup because it is what I have on hand.  The controller is not true RS422.  The manual is very vague, but what I get out of it is that when the differential voltage is above +2.5 V, the drive activates the motor, and when the differential voltage is below +2.5 V, it deactivates the motor.

[nyc_(is_out_of_here)]

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@sullivnc wrote:

Obviously there are other ways to do it.  I asked about this specific setup because it is what I have on hand.  The controller is not true RS422.  The manual is very vague, but what I get out of it is that when the differential voltage is above +2.5 V, the drive activates the motor, and when the differential voltage is below +2.5 V, it deactivates the motor.

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"What I have on hand" is a silly reason to give for using a piece of equipment if you knew electronics would know does not make sense.

Sounds like a DAQ is required.  I have no idea why you would even think a GPIB-232CV-A would be a good idea.

[Dennis_Knutson]

From your description, it's not even close to RS422. If you don't understand the manual, it's silly to ask about the device ashen you don't mention the make and model or attach the manual.

[sullivnc]

The manual says to use either an open collector or RS422 controller to achieve the desired signal.  My boss asked me to try and do it with the hardware on hand, which is why I asked the question about using an RS232 converter with an RS422 converter.  I'm not pulling this out of nowhere.  See attached link for the controller manual.  See page 19.

ftp://ftp.phytron.de/manuals/power_stages/msd-gb.pdf

[crossrulz]

To be technical, RS-422 just describes the electrical characteristics of the bus.  What we are used to for RS-232 and RS-422 is a UART protocol being transmitted on the bus.  But based on your description, I would get a small IC that takes a single ended digital signal and makes the RS-422 differential signal.  Then you just contol it with a single digtal line.

[nyc_(is_out_of_here)]

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@sullivnc wrote:

The manual says to use either an open collector or RS422 controller to achieve the desired signal.  My boss asked me to try and do it with the hardware on hand, which is why I asked the question about using an RS232 converter with an RS422 converter.  I'm not pulling this out of nowhere.  See attached link for the controller manual.  See page 19.

ftp://ftp.phytron.de/manuals/power_stages/msd-gb.pdf

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Do you have an electronic background?

You should be concentrating on page 19 of that manual. Do you understand what it *means* ?

If you don't want to mess around with building your own circuits simply buy a TTL to RS422 converter.

http://www.commfront.com/rs232-rs485-rs422-serial-converters/rs232-rs485-rs422-to-ttl-converters.htm

[Maria14]

Hi, I have -let's say- a similar problem here. I have a card to test using CRio. First of all I tested my card under Windows using VISA protocols. but now I wanna do this test directly using CRio so for sure I'm not going to use VISA protocols and port COM as I did under Windows... would u please give me some astuces to read my results? I tried to attach my card directly to CRio but nothing happenend (it's not suplying)

[SteveD123]

The original poster made the mistake of assuming that the existence of a 25 way D connector implies that there is an entire system to read commands and respond to them. The linked manual's description of the electrical interface is in fact entirely clear, no RS 232 or 422 interface is present.

Could you give some more details about what you are trying to do? What is the card you are testing and what CRio hardware do you propose to use?