Hi Allan

Thanks for coming back in. The motor and drive links are below. I cant attached the manual the file is too large so I have sent a link to it.

https://www.schneider-electric.co.uk/en/product/LXM28AU07M3X/motion-servo-drive---lexium-28---single-and-three-phase-200...230-v---750-w/

https://www.schneider-electric.com/en/product/BCH2LF0733CA5C/servo-motor-bch---80mm---750w---w-oil-seal---w-key---leads-con/

https://download.schneider-electric.com/files?p_enDocType=User+guide&p_File_Name=LXM28A_Manual_V2.1_EN.pdf&p_Doc_Ref=0198441114054-EN&_ga=2.266361352.789260454.1534532339-227965827.1533213090

Cheers
Mick

Hi,
looks like Allan has it right the synthesized encoder outputs are line driver, see pg 156 of:

http://download.schneider-electric.com/files?p_enDocType=User guide&p_File_Name=EIO0000002305.02.pdf&p_Doc_Ref=EIO0000002305&_ga=2.101965250.2111833376.1534533331-1177742663.1534533331


I see that the driver can swing a few volts only. Is that enough for the CSMIO?

Craig

Mick

Thanks.

The 6 ESM outputs are RS422 line drivers, which is the desired differential form at at nominally 5V levels. You can and should connect these directly to the CSMIO encoder inputs of the same name. You should use twisted pairs, preferably screened. 24awg (1/0.2mm2)Screened Cat5 cable is convenient for this.

I cannot see that any +5V connection from the CSMIO is needed, though I've just had a quick peep so far.

Craig

You just beat me to it. Yes, RS422 is ideal for the CSMIO.

Allan

Hi Allan,
kool. I would have thought that the CSMIO and the servo drive would have to share the same earth potential.
I know the output of the drive is differential but to allow an undefined zero point would require the CSMIO be able to tolerate
a common mode voltage outside its own power supply rails and require that it have sufficient common mode rejection ratio that
the common mode voltage does not swamp the signal.

Craig

Hi Allan

Great news, thanks for taking the time again and proving a rapid clear answer. I will be using the pre-wired sub d 50 CN1 cables. I did order them but haven't arrived yet .  Will get the motors and drives fitted over the weekend and delve into the operating manual.  

Cheers
Mick

Craig/Mick

I'd only spent 5 minutes  or so with the manual  before writing my last post. Mick had previously asked about the 5V and that seemed pretty obvious as there was no 5V input line on the drive, or if there was then I missed it.

I agree totally that one would not want different 0V systems for the CSMIO and the drive. Excessive common mode levels could cause erratic behaviour or even physical damage in the worst case. CSMIO has 0V outputs on the encoder connector which should of course be tied to the ground reference for the  ESM drivers. I do this with my Kincos. But with Mick's drive I wasn't at all sure where this connction would best me made and need more time to see if the manual clears this up anywhere. It was not obvious to me at first sight. There is also the question of what signals are within the made up ESM cable to the CSMIO and whether these include 0V.

Allan

Allan Craig

Thanks for expanding on this. Am I right in thinking we are talking about GND Pins on the CSMIO not being used, the potential issue. Eg pins 17,21,25 on the encoder inputs?

Would this be something Cs Labs could help with or maybe Schneider Technical? The issue with talking to Schneider technical would be my lack of knowledge in circuits .   

 

Cheers
Mick

Mick

Yes, the GND pins you mention above are what we are talking about. Essentially, we are saying that this ground potential must also be the one used by the drive as a reference for its ESM outputs.

I haven't had time to give the manual much attention as yet but it looks as if pin 49 on CN1 is the only common ground for  all of the drive's digital signals. It is also the common for the 24V power supply to the drive. As we don't want to contaminate any of the analogue grounds with digital noise, pin 49 appears to be the only option.

Assuming you are using the same 24V supply for the drives and for CSMIO, their commons are bound to be connected, and that, in essense, should be enough. If you have separate 24V supplies, make sure that their 0V commons are connected together. If the cable you are using has a ground wire, by all means connect it to one of the CSMIO ground pins. If it only contains the 6 ESM signals, just make sure the power supply ground is common for the CSMIO and the drives as above. It is unlikely that you will experience noise issues on these differential signals, and unless you do, I wouldn’t worry about it any further.   

Allan

P.S. I somewhat sloppily tend to use the workds ground and common interchangeably. To be clear, in both cases I am referring to the circuit 0V line, and not to the protective earth (though these will likely be bonded somewhere).

Hi Craig

Ok I think that makes sense. I will be using the same 24v power supply so this shouldn't be an issue. I really need to do some more research on the difference between GND, COMMON, 0V.

Cheers
Mick

Hi,
I' guessing hat if you have the setup software installed on a PC you can not only program the drive but you can run it, that is to say
have it move to indexed positions or accelerate to a given speed without the need for the CSMIO. Certainly the Allen Bradley software allows
such use. You can use the built in software scope to tune the servo. In your case you really only need to tune the velocity loop and the chances
are that the default tuning is going to be that close to perfect as is, you could make it worse but unlikely you could improve it.

Either way it is a fun way to use your servos and get familiar with them without having an external controller.

Craig