On-Motherboard Modbus / RS485 connection

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29 Mar 2016 22:20 - 29 Mar 2016 22:40 #72351 by andypugh
I have swapped my Lovato 3hp VFD for a Huangyang 4hp VFD as the Lovato had no RS485 protocol definition, and over-currented when running my lathe spindle motor. The HY VFDs have an already-written HAL component for control.

Using a USB RS485 dongle it turned out to be far too easy to get the spindle turning, so I decided that I would make things more difficult.

The USB dongle looked like this and cost a couple of £ from eBay.







It stuck a long way out of the computer, and didn't really suit my installation, where the motherboard is simply fastened to the back of the control cabinet of the lathe. I decided to try to connect it to one of the motherboard headers.

Fortunately the USB connector pin ordering is the same as the motherboard header (probably not a major surprise) so I was able to solder a bit of header strip (with the pins bent through 90 degrees) onto the dongle in place of the USB plug.







And then I could mount the whole thing on the motherboard, saving a USB connector and also avoiding several DB9s (which all the other options seem to require).





I intend to replace the screw terminals too, so that I can have a gnd/shield on the cable.
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Last edit: 29 Mar 2016 22:40 by andypugh.
The following user(s) said Thank You: PKM, jtc

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04 Apr 2016 20:25 #72737 by cncnoob1979
Andy,

That is a great idea! I just replaced my motherboard and space is tight. Which one did you buy? I wonder if "most" usb / RS485 dongle's will work?

This will free up a serial connection and make this a more "clean" installation. I found the Huangyang VFD was picky about it's Modbus connectivity with a ground ran from the RS485 to the VFD. So I cut the ground wire from the RS485 and only connected the ground to my VFD. I had multiple failed errors during operation until I did this.

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04 Apr 2016 21:56 #72744 by andypugh

Which one did you buy?


www.ebay.co.uk/itm/121106393167

(though it is, of course, no longer a valid listing)

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04 Apr 2016 22:47 #72749 by cncnoob1979
Thanks Andy,

I just bought one like it!

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05 Dec 2022 12:00 #258579 by akg1904
Hi Andy,

I recently brought the same USB RS 485 dongle and want to integrate my milling configuration with it. it would be great if you could share how you integrated it to your system and guide me through it.

Thanks
Abhishek

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05 Dec 2022 12:43 #258588 by andypugh
It is more important to know what you are connecting to. I am using a Huang Yang VFD so the hy_vfd HAL component does all the work.

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06 Dec 2022 08:52 #258681 by akg1904
Hi Andy,
Thanks for your quick reply.

I am using Delta MS 300 VFD and I have already tested it in Windows(with same MODBUS RTU) and it is working fine.
But as I am new to LinuxCNC,thus I don't no how to integrate it with linuxCNC.
I have gone through many post where they have implemented Modbus and created specific HAL and spindle INI but for some reason it's not working for me and I saw this post where you are using same USB RS 485 dongle,so it will be very helpful if you could guide me.

Thanks & Regards
Abhishek

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06 Dec 2022 09:45 #258684 by andypugh
Does this HAL component look like it would help?
linuxcnc.org/docs/stable/html/man/man1/vfdb_vfd.1.html

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06 Dec 2022 19:56 #258733 by Roguish
I have a Delta VFD-E, and use the vfdb_vfd comp.
It was created for a Delta VFD-B, but works for me.
The modbus addresses and commands are the same.
you should check it out.....
It was pretty easy to set up.

Andy's USB hack is pretty clever. I may try it.

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