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Author Topic: modbus vs psm or which is what?  (Read 5317 times)

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modbus vs psm or which is what?
« on: March 22, 2015, 04:31:08 PM »
I have been running a delta vfd-m and 2.2kw GMT spindle combo on a cnc router setup for about a year or so without control from mach 3.
I tried without success to use a pmdx 107 added on to my pmdx 126 when we were just getting set up but abandoned the trial to get some work churned out.
I recently had to replace a computer and decided to revisit this.
I'm far from an electrical engineer so talk down to me, you won't hurt my feelings.
When I first started the build I somehow didn't take notice of modbus control but now I see all kinds of info. I assumed I wanted pwm signal control but now I'm really confused.
My first question is which is the better method to control the spindle speed and on off process?
The delta m specs state it has built in modbus communications.
Re: modbus vs psm or which is what?
« Reply #1 on: March 22, 2015, 05:31:52 PM »
If your VFD has Modbus, use that as it will be more accurate than using PWM.

Cheers,

Peter
----------------------------------------------------
Homann Designs
http://www.homanndesigns.com
email: peter at homanndesigns.com
Re: modbus vs psm or which is what?
« Reply #2 on: March 22, 2015, 05:37:52 PM »
Thanks, Peter

Now next question.
It looks like I go directly from the vfd to the computer and not to the breakout board for modbus connection correct?

Bear with me here I'm just getting the picture on the modbus thing. Wish I'd looked into this more closely before.


« Last Edit: March 22, 2015, 05:49:33 PM by snglittlerock »
Re: modbus vs psm or which is what?
« Reply #3 on: March 23, 2015, 07:50:17 AM »
Yes, that's correct. You will need a rs232 to Rs485 converter.

Then lots of reading of the VFD manual.
You then need to set up the modbus transactions to get the data to/from the VFD.
You then need to write a Mach3 brain or two to interface between Mach3 and the modbus registers.

Have a look at this article I wrote. Hopefully there is enough information to gt you started.
http://www.homanndesigns.com/pdfs/Using_Modbus_with_Mach3.pdf


Cheers,

Peter
----------------------------------------------------
Homann Designs
http://www.homanndesigns.com
email: peter at homanndesigns.com
Re: modbus vs psm or which is what?
« Reply #4 on: March 23, 2015, 05:53:03 PM »
Well thanks again.

I started reading that document late last night. Good stuff. Didn't make it to far but Ill keep hacking away at this.

In my research on my particular VFD I have a RJ11 plug for MODBUS built in so Ill need to go from RJ11 to RS485 I suppose. Delta actually shows such a thing in a support document but I haven't checked availability just yet.

After last weeks problems (computer crash, upgrade to ESS etc..) Id be willing shell out a little cash for someone to give me what I need to get this thing set up. The manual alone makes my head hurt.
There doesn't seem to be anyone in the area that knows enough to want to tackle it.
Re: modbus vs psm or which is what?
« Reply #5 on: March 25, 2015, 11:36:39 AM »
Can I go from the RJ11 to a DB9 so long as I know which pin is where at both ends? I'm having trouble finding the RJ11 to RS485. Am I dong more than getting a wire from point a to point b. I had already ordered an RS232 to RS485 converter so Ill at lease have that on hand. There is an RJ11 to RS232 converter. Seems like a lot of connections to fail.