From learnings on a posting making my Ultimaker original twisting the stepper motor cables

[Grant_Macaulay]

From learnings on a posting making my Ultimaker original twisting the stepper motor cables is an advantage to reducing noise and increasing performance. So here is a few pictures on how to twist some stepper motor cables efficiently on my Shapeoko2 CNC and which I am going to do to my Ultimaker original also
Merry Christmas!!

Originally shared by Grant Macaulay

So the Shapeoko2 arrives with loose wires on the stepper motors, and from the learnings from building a 3D printer, noise can make a big difference to the final product and performance of the stepper motors. So twisted stepper motor wires are called for!!

1. create a twisting jig for the cordless screwdriver.
2. twist one pair of coil wires clockwise. In this case the Green & Black cables. Then the second pair clockwise also. (Blue & Red)
3. then twist the two pairs together ANTI clockwise. So it all works together stopping any unwinding

Merry Christmas !!

[Stephanie_A]

I’m assuming that you are twisting each pair together? Then twisting those?

[Electra_Flarefire]

I ended up just loosely plaiting all my wires to keep them neat and together. I wonder how much difference this will really make. I’d have thought this kind of coupling would have made things worse for the motor. But it definitely will keep down the interference from the motors on the other control lines.

[Grant_Macaulay]

I thought this was a good update. From the CNC noise discussion.

Noise was an issue I spent some time overcoming with my electronics. I am not sure if I tried twisting my motor leads, or not. My solution was much different than that though. I settled on optically isolating my step, and direction, control lines. That cleared everything up for me.

Before I did that noise was coming out of my drives, and propagating into all of my other control electronics, wreaking havoc on system operation. Stopping that noise from entering my system at the source, the drives themselves, fixed everything for me.

The motor side of things is not really sensitive to noise. Although it is where the noise comes from. That noise is going to be in the drive board before it even gets to the motor leads too. You can’t really twist your drive board up either to eliminate it.

Physically isolating my control signals did the trick for me though. Noise could not jump the optocouplers. Plus optocouplers need quite a bit of current by themselves to trigger on. So they add immunity by way of hysteresis by themselves. A little spike is not going to phase an optocoupler. It will phase logic electronics though. Sensitivity between the devices is orders of maginitude different. Sometimes a dull knife is the solution.

At least it was for me! I have noticed a lot (all?) of higher end stepper drives have optically isolated control lines too. So it isn’t like I invented anything here, I just rediscovered it for myself.

Here’s a snippet of one of my motor drive schematics with the optical isolation circuit in it. http://i.imgur.com/wmbrCVI.png There really is not quite enough of the circuit to clearly understand it. The optocoupler is triggered on a low input line, the anode is held high. This causes a high output on a low input. Then the output of the optocoupler goes through a Schmitt inverter to square it back up, and invert it again. Optocouplers naturally have slouching signal shoulders. So for a crisp waveform a Schmitt trigger is essential.

Anyhow, this comment is turning into a book so I’ll end it here with an oscilogram of the corrupted step signal before it was optically isolated
http://i.imgur.com/JVyX6n5.jpg For the after signal just imagine a clean square wave.
Noise was an issue I spent some time overcoming with my electronics. I am not sure if I tried twisting my motor leads, or not. My solution was much different than that though. I settled on optically isolating my step, and direction, control lines. That cleared everything up for me.

Before I did that noise was coming out of my drives, and propagating into all of my other control electronics, wreaking havoc on system operation. Stopping that noise from entering my system at the source, the drives themselves, fixed everything for me.

The motor side of things is not really sensitive to noise. Although it is where the noise comes from. That noise is going to be in the drive board before it even gets to the motor leads too. You can’t really twist your drive board up either to eliminate it.

Physically isolating my control signals did the trick for me though. Noise could not jump the optocouplers. Plus optocouplers need quite a bit of current by themselves to trigger on. So they add immunity by way of hysteresis by themselves. A little spike is not going to phase an optocoupler. It will phase logic electronics though. Sensitivity between the devices is orders of maginitude different. Sometimes a dull knife is the solution.

At least it was for me! I have noticed a lot (all?) of higher end stepper drives have optically isolated control lines too. So it isn’t like I invented anything here, I just rediscovered it for myself.

Here’s a snippet of one of my motor drive schematics with the optical isolation circuit in it. http://i.imgur.com/wmbrCVI.png There really is not quite enough of the circuit to clearly understand it. The optocoupler is triggered on a low input line, the anode is held high. This causes a high output on a low input. Then the output of the optocoupler goes through a Schmitt inverter to square it back up, and invert it again. Optocouplers naturally have slouching signal shoulders. So for a crisp waveform a Schmitt trigger is essential.

Anyhow, this comment is turning into a book so I’ll end it here with an oscilogram of the corrupted step signal before it was optically isolated
http://i.imgur.com/JVyX6n5.jpg For the after signal just imagine a clean square wave.

[Stephanie_A]

But this would mean that the noise was coming past the stepper motor controller, which surprises me. I would have thought that they would have adequate isolation.