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Author Topic: Serial/Modbus-servo comunication.  (Read 5123 times)

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Serial/Modbus-servo comunication.
« on: October 05, 2007, 11:03:42 AM »
First Hi to all.

I just download M3 and between other things I see  the serial and Modbus.

There is any way that M3 can send the data to the servos, thru serial instead step and direction?
Or can M3 poll the servos for info - to create a complete close loop system?

Dan

Offline Whacko

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Re: Serial/Modbus-servo comunication.
« Reply #1 on: October 06, 2007, 02:25:00 PM »
Modbus will be too slow for servo loop update. Best check out the TCP version available with the new download.

Whacko for TCP
Nothing's impossible
Re: Serial/Modbus-servo comunication.
« Reply #2 on: October 07, 2007, 02:27:25 PM »
Hi,

The loop is closed by the servos so communication speed is not an issue.
Modbus or serial (ASCII)  is used just to send target positions(not steps) to the servo and to get the actual position from the servo.
Once the servo has the values Mach just needs to monitor the status and the position.

Right now Mach spends most of the time sending out the steps. This is perfect for steppers but is a limitation for servos.

So again what is the Modbus or serial used in Mach3 for?

Thank you,

Dan

Offline Whacko

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Re: Serial/Modbus-servo comunication.
« Reply #3 on: October 07, 2007, 02:45:00 PM »
Speed is of absolute essence with encoder loop position feed back. Speed in this case, the communication speed, or "data through put". The modbus will be way too slow for positional closed loop. That is presumed that the question you asked was to exclude the parallel port interface. The Modbus is an industry standard plc serial interface to expand i/o. In some cases it might be possible if the movement of the machine is slow enough, or if cv travel is not essential.
Mach3 can work in positional closed loop mode as it is currently.

Whacko
Nothing's impossible
Re: Serial/Modbus-servo comunication.
« Reply #4 on: October 07, 2007, 06:25:52 PM »
Whacko,

First thank for the help.
There is no argument here, that the Modbus is slow for the positional loop. But like I said, the poz loop is the servo driver's job.

So is Mach3 capable to sent values(not step and direction signals) to a servo?.
If yes how is this achieved?. At this time I have only the free verison
I can't find to much info in the manual, or on the forum. There is any other place were should I look?

Thank you,

Dan

Offline Chaoticone

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Re: Serial/Modbus-servo comunication.
« Reply #5 on: October 07, 2007, 09:37:18 PM »
Hey Dan, have a look at this link, I hope it helps.

http://www.rogersmachine.net/encoderinterface.html

Brett
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My guard dog is not what you need to worry about!

Offline Chip

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Re: Serial/Modbus-servo comunication.
« Reply #6 on: October 07, 2007, 09:39:56 PM »
Hi, Dan

Can you ex-plane your servo setup, Is it +- 10 volt control ?, There are cards for Step-Dir to +-10 & +-5 volts.

Dose it have a CPU to controls/coordinate the moves ?

Thanks, Chip
Re: Serial/Modbus-servo comunication.
« Reply #7 on: October 07, 2007, 10:06:08 PM »
There are ways to make Mach3 send me moves over RS232 but you need to have a contouring buffer in the drive and blah blah blah... I did it with Smart motors but I can tell you that it is no fun and you need to be a C programmer to get it working ;(
Fixing problems one post at a time ;)

www.newfangledsolutions.com
www.machsupport.com

Offline Whacko

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Re: Serial/Modbus-servo comunication.
« Reply #8 on: October 09, 2007, 01:57:58 PM »
Hi Dan,

It is as Brian said. I know what you want to do, and there are smart drives that except position commands, but then you will need a post processor or macro running to convert the data to your drive's command syntax. You will also have a huge latency between Mach3 and your servo drive controllers.
But technically you will not have a closed loop with Mach3, as the speed and coordinates will be out of Mach3's control. Is this what you mean?

Whacko
Nothing's impossible