Analog output to rexroth vt3006 card

[JustinCochran]

Hey all. I've stared a new project and am giving myself a good headache trying to wrap my brain around this probably simple problem. I have a rexroth vt3006-s-30 card controlling two valves for a hydraulic  cylinder to move in and out. Looks like the old plc that wasn't there anymore may have had analog output to rexroth card. Has anyone dealt with rexroth vt3006 cards and controlling them with visilogic? My carriage that cylinder operates has 4 prox switches that I was trying to perhaps use for different stages of where carriage is. Is there perhaps easier way to control valves without the card and using visilogic program to do same thing as the rexroth card? Any thoughts? Thanks for any and all responses.

[Ausman]

Hi Justin,

Never used one, but although this isn't a specific answer, you perhaps should have a good read of this topic; 

There are many relevant posts in this topic that might help you out in controlling it directly. 

However, and this is a big however, quickly looking at the card's specs I think you will be easiest retaining it as the intermediary.  You will definitely need to wrap your head around how it works before starting any programming work. 

Hopefully, others here will have better knowledge of the device, or other ideas.

cheers,

Aus.

 

 

[JustinCochran]

Thanks for the response. I'd like to add that there also is/was an analog relay block that has dip switches set for an input of 4-20ma, and output of +/- 10v. I know the output from this relay went to card. I'm assuming the input came from old plc system. I know I can probably use analog output from my snap on module to input of the relay. Just trying to think how I can code it to work properly. All wires that were on card are still where they went. I have the 24vdc input power, both solenoids to proper terminals, and that one input to card from the output of +/-10v from analog relay block. I have some what of an idea in my head, too hard to explain though. It involves using the 4 prox switches and increments to output. Just for simplicity, my 4 inputs are down, almost down, up, and almost up. I'm also thinking of using 4 of my outputs to control each stage. If anyone has dealt with something similar, I'd appreciate any advice on how to go about this. Thanks.

[Joe Tauser]

You're going to need an external converter to create the +/- 10V.  Unitronics analog outputs are single ended.

Post your code after you've beat on it a while and we can review it.

Joe T.

[JustinCochran]

I'm guessing that is what this little relay is. Haven't been able to find much info on it yet. I do know it has a 24vdc power input, 4-20 ma input and a +/- 10v output. The output went to vt card, rest of it wasn't hooked up.  I'm drawing a blank on how to even begin the coding for this. Im a fish out of water on this one. Any examples of this type of control or anyone have an idea how to begin?

[JustinCochran]

Just want to update this topic for future reference to anyone else that comes across this or something similiar. Much thanks to Joe for calling and going over some of this and getting me started in right direction.

Today I powered up my plc and used an analog output from my snap in module (4-20ma) to the analog input of analog converter box. It was already setup for 4-20ma on converter input. In coding I made X of analog output -100 to 100. I hooked up voltmeter to output of the converter. The output is setup for +/- 10v. While changing my X in program, I could see the voltage move from -10 to 10 on output of converter. I next ran wires from converter to the vt card analog input. Reading a positive voltage of any kind puts 24vdc to one solenoid while a negative voltage energizes other solenoid. I didn't have the solenoids hooked up though, just testing the output on the vt3006 card. That's as far as I got so far. Will do more testing next week.

[Ausman]

Hey Justin,

good news on that.  I suppose that you saw this post....?    It didn't register with me until the braincells flopped over and shorted today.

cheers,

Aus

[JustinCochran]

Yes, I did read that. Thanks for referencing it again though, I hadn't noticed that for future I can use the IO-AI2AO4 module to accomplish this without the analog converter. This is first time I've ever dealt with analog outputs. I've done several analog inputs for leak testers using pressure transducers. I still have much to learn.

[JustinCochran]

So I connected the solenoids to the vt card yesterday. Just for safety precaution I put power to card through a push button in case it tried to move too fast on me. I started by inputting my X on analog output and it works properly. The higher the number faster it moves and same way in the negative. So I wrote the code using the 4 prox switches as stages for a different setting to be stored into analog output and it works great.