I’m thinking of rewiring this whole thing with Cat5/6 stranded, as I’ve heard there are issues with crosstalk/signal inductance with standard wiring, and Cat5 was designed exactly to negate signal inductance.
I’m thinking of making some changes or additions to the stepper motor mounts to allow standard Cat5 jacks, then it’d be an easy matter to hookup/swap motors etc.
Good idea?
I am planning on using Cat 5E for an MPCNC I am in the process of building. My expectation is that it the shielding will reduce interference of the electrical signals. The disadvantage is that it is 24AWG wire (stepper wiring is usually 22AWG). The idea of adding jacks is intriguing. I believe that there was a design on Thingiverse for a mount that fit into the tube ends.
I did this on mine but not professionally. I never printed the mounts for the jacks. I am using Cat 5e (stripped) and RJ45 jacks (zip tied and taped into place). It is ugly but it works. When I redo my setup in the near future I will replace the RJ 45 jacks with the more common 4 pin connectors for Stepper motors. I just don’t like the bulk and the look of the RJ45s. I also suspect connection issues during movement.
With my current setup I used 4 of the 8 wires for the steppers. I was going to use the other wires for endstops etc. but when I redo my setup I may just use all 8 wires for the steppers. Not sure yet. I get some missed steps every once in a while. I don’t like that. I suspect the wiring and or the jacks might be the problem.
i tried running TTL signal through the cat 5e cable that runs to the Z motor. That does work. So that’s nice. I also tried running 12 volt 3 amp power for the laser. Yeah that didn’t work. Not so nice.
Also if you use cat 5 or 6 cable you will need to use cable chains. The tape measure trick doesn’t work unless you strip the shielding off the cables because it is too thick and ridged.
Those are my experiences. Hope the info is useful.
Edit: my problem may also be interference because I stripped the shielding off the cables to make the tape measure cable management work.
Nice! Yeah, it’s not really the shielding itself that makes Cat5 or 6 work well to negate crosstalk/inductance, it is the differing rate of twist among the four pairs of wires.
The shielding will block a lot of inductance from AC or neighboring cables, as well as RF.
I’ll look on thingiverse! Thanks!
There should be no issues. The issues that do pop up are the long LCD cables we use and bundling them tightly with other power wires. The biggest issue with noise has been import spindles.
Jacks are good and will work but I do not believe you will be solving any issues with them.
They did make it stupid easy to pull the cables when I upgraded to the burly parts.
I built mine with cat5 first but quickly discovered that connectors are like moving parts, each one is a failure point waiting to happen. If I really needed to use it again I would double the wires and pins so each stepper wire would go to two rj45 pins, each to one side of a twisted pair for redundancy. I have been much happier with locking JST’s.
That’s how mine are wired. Each color pair is a single stepper wire color. So far I’ve not had any issues with the connectors and my mpcnc has been using them since 2016.
I think the major advantage would be consolidation of signals into one cable, for things such as the upgrade to Burly parts (which I have yet to do). I would not personally worry about connectors if you use a good quality keystone punchdown like Barry shows. After all, these are in common use in networked systems, and robotics, plus the current draw for these steppers does not exceed either the Cat5e or connector specs.
As for crosstalk, the only reason the twisted pair is superior is because each pair is used with differential signalling. This allows the receiver in ethernet systems to cancel out any injected noise. Stepper signals are NOT differential and so any shielding you’d get would be from a shield on the Cat5e cable, if you actually use a shielded cable and ground it properly.
I’ve had zero problems with crosstalk to steppers as Ryan pointed out. I’ve been running a 30" X 45" machine for 18 months with no problems at all using extended servo wires.
Seems to me that RJ45 should be well constrained so the male connector is not moving in relation to the female. And you are going to get stuff working it’s way into the interface eventually. Serial d-sub connectors or the round aircraft type connectors are likely a lot better for this application.
I’d love to use canon plugs on the mpcnc, had lots of experience with them, but damn they’re expensive! It’s still down to the wiring though. You’d need to use shielded wires, which will be stiffer. It’s not a big deal on mine, since the wires just fall off the side of the table, no cable chain for me! Shielded cat-5 or 6, will most likely be solid core wire, I don’t think I’ve ever seen shielded patch cables. I’m not talking twisted pair, but actual grounded foil or wire strand shielded cable.
I’m wishing that I hadn’t donated a huge spool of shielded solid Cat6 to my local makerspace. Honestly it might still be sitting on a shelf there so I might go grab a 30’ section. I have some 9-pin connectors which should be good if doubling them up, or am I not following this properly? I can split the signal across the Cat-6 then rejoin them at the ends before soldering to the other side, right?
just solder two wires to each connector pin
Oh, I was thinking the 4 wires coming out of the controller would each be split to 2 pins, then travel across the Cat-6 “split” then be recombined on the other end. I would just create two adapters (9-pin to stepper) for each axis. Am I still just lost?
Now that I think of it, that Cat-6 was awfully stiff, not sure it would be a good option with it needing to flex along with the gantry motion.
But is my logic above still good in theory?
Don’t use solid core cat-anything. Use patch cables. The solid core stuff you run through the walls will work harden and break after a bit of use.
Good idea if you actually experience some problems with crosstalk (which basically never happens).
Otherwise it’s a lot of work, time and money for no gain whatsoever and possible drawbacks. Since you basically never have to swap your motors anyways, and whenever it happens it takes less than 10 minutes to properly solder a new one.
There are some disadvantages to use ethernet cables also: they are much more bulkier, can tolerate less current, are less flexible, the connectors introduce some possible issues (I was using the same as Barry, they are nice but they don’t like being rewired too often) and it makes it hard to change your machine size.
I’d say don’t even bother doing that unless you really have problems, which are generally EMF if you’re using a cheapo router or a cheapo shop vac. And even so, I’d recommend using some actual shielded cables with embedded copper sleeves instead of this, that’s what I ended up doing after several iterations (but I had a good reason for using those: plasma cutter). I started my build using ethernet cables and had to ditch them because they were not shielding properly, plus it wasn’t reliable.
Just use some regular wires, twist the pairs using a drill and solder everything, it will save you a lot of headaches and you’ll have a very reliable machine.
