Closed loop stepper cable questions...

Hi Tommy,

I can only interpret that as you clearly weren't feeding your pup enough Lenovo branded "Charger kibble", the lack of power in the relationship must've been something that needed to be addressed. Although I don't approve of his violent coup d'état (that's apparently French dog for bite.

The mini matriarch here is both approving of the "white fluffiness" and in her animal obsessed way, asked if the puppy is ok after eating the charger.

Back to me though, because I'm more qualified to talk about that than most stuff here...

Well after muttering incomprehensively for hours in the garage, (and only incidentally testing stuff) I have learned a few things:

1. Some variations of VGA extension cables don't use pin 11 or 12 (one of the 6 pins chosen by StepperOnline to wire their motors through. I had no connectivity on pin 11.... so.... that was suggestive of a problem.

Moral to this story, don't assume every VGA extension cable will work as encoder cables. I had one type with no connection on pin 11, another with no connection on pin 12, and another with no connection on either.

Why oh why didn't StepperOnline use the commonly used pins?.. or better yet, an RS232 or DB9 plug (all the pins are wired).

2. I am truly abysmal at soldering VGA plugs. I used a length of CAT6 cable, and a male/female pair of VGA (DB15HD) plugs to create a test "extension cord" for the encoder. I certainly wouldn't use it in a production environment... but it's something some others building their DIY CNC might consider "a factor" when buying a closed loop stepper kit.

3. My 20 year old, beaten up, "Fat tipped" 40W soldering iron is probably not the best piece of kit for finer soldering work. I'm honestly surprised I've gotten this far with it.

....Frankly, a few VGA male and female plug to screw terminal boards are looking pretty good about now.

Anyway, I have tracked the problem down. Thanks for the suggestions!

P.S. I have to say that I'm not overly convinced about Stepper Online's closed loop cables at this point. A little thought could make them SO much better (longer thread on the aviation plugs so we can mount them to cabinets thicker than 0.5mm, offering an honest to goodness extension cord with a plug at BOTH ends, proper shielding with earthing points... you know.. stuff that helps... a lot).

Anyway, I'm probably going to be making my own cables, from here... so maybe others can save themselves some pain and might consider doing the same.

I hope the somewhat painfully earned lessons help someone else out there.

Take care.
Hamish

I would say StepperOnline did well preventing People using Standard VGA extention cables. These cables are not intended to be used in drag chain environment.
So preventing the use of this cables is preventing problems.

Ovi Hiris at treotham.com.au could help with drag chain compatible wiring...
 

Hi Itsme,

You raise an interesting point. Others will no doubt find it helpful. However, I'm sorry, I left some key information out of my description. I did not mean to suggest using VGA cables in the drag chain as you inferred. That's my fault.

So let's be clear here:

My CNC router design has a control box/trolley that's completely separate and detachable from the machine. This is mostly for storage purposes, but could enable the control system to be moved and linked up to differing machines (obviously one at a time, with individual LinuxCNC configurations) and/or repurposed easily without significant internal rewiring.

Back to the VGA cable:

I'm not trying to use the VGA extension cables in the drag chain, merely to bridge the gap between the wall mounted sockets of my control box, to another bunch of panel-mounted sockets on the device itself. Using a VGA cable for this purpose shouldn't have the constant flexing that the drag chain that you're worried about.

From there, the usual Stepper Online provided cables will be used in the drag chain.... Or at least, that is the current plan. I wanted everything to be modular so storage, diagnostics and replacements were easier.

Of course, this is all theoretical at present... I'm only using the VGA cables for testing motor connections/function as I have no machine, or even drag chain at this point.

I hope that clears things up, and I will try to be clearer about what I'm trying to do in future. Your thought about NOT using VGA in the drag chain was a good one.

Kind Regards,
Hamish.

Hi Rod,

Thanks for the link, I have the Stepper Online cables for the drag chain part, but I don't have the right stuff for the limit switches and touch probe. So I'll check Treotham out. However, since I haven't even started assembly on the machine itself yet... I've probably got some way to go before I'm up to that bit.

How's your "space ship" going? Are you doing anything fun with it these days? I'm still dreaming of running my first job, so I have to live vicariously through others.

Hope you're well and enjoying the machine!
Hamish.

It took me a few tries to figure out the StepperOnline encoder cables (at the motors) do NOT have the same color coding as their extension cables.  The cables are nice(ish), good rubber sheathing (not PVC), fine strand for flexibility... but you're right about the shielding.

My solution was to chop the VGA connectors off close to the motors and terminate with aviation connectors that permit tying the encoder cable shield to the extension cable shield and on to chassis ground next to the drives.  I don't have many miles on them yet, but so far no noise issues.

And yes, the steppers acted WAY unhappy when the encoders were cross-wired until I figured out the colors don't match and that I had a few of them crossed up.

Bonus Tip - change the permitted following error in the drive software.  I can't remember what the actual setting field is named, but default is something like 1000 counts and can result in huge mechanical deviation with no drive alarm.

-Ralph