Power, Stepper, and Signal Cable Lengths

[amishx64]

I am gathering parts for my next big CNC build.

I have purchased the following:

• 1x PS-10N50 - 50VDC 1000W PSU from Antek Inc. for stepper drive power.
• 4x Centent CN0142 Anti-Resonance Microstep Drivers
• 75FT 24AWG Cat5e cable for signal from PC to drivers for step and direction
• 100ft 14AWG CL2 Rated 4-Conductor for connecting the drivers to the steppers
• 2-conductor cable for stepper driver power connections

I am wondering about the best way to locate all of the components. I can see two options:

1. Put all the components on a cart and run three lengths of the 4-conductor stepper cable OR
2. place the stepper drivers near the stepper motors ON the CNC frame and run three lengths of 50V power lines as well as signal lines from my cart to the drivers, individually.

Wire is expensive and I want to ensure that I have clear signals, so I am leaning towards option #1. The only thing that worries me is that there may be a higher impedance or lost steps due to long stepper cables.

Option #2 would be fine except I have read that it is important to also keep the driver power supply cables as short as possible as well as the PC to stepper driver signal cables to eliminate cross-talk, etc.

The cart will likely only be a max of 10ft or so away form the CNC. The cart is where all the other electronics are going to reside.

Any suggestions? Which option do I choose?

[amishx64]

In the interest of getting opinions and avoiding wordiness, here is a diagram.

[doorknob]

I would prefer option #1 because I would want to minimize the possibility of noise pickup on the step and direction signal lines (which could lead to spurious axis motion), and I would also prefer to keep sharp edges on those pulses. With option #1, the length of cable carrying the step signals would be kept relatively short, which should minimize their exposure to noise pickup, and should also prevent the softening of the pulse edges. I would not expect the ten-foot-long 4-conductor cables going to each of the stepper motors to pick up noise (however it's possible that they could radiate electrical noise which could be picked up by other electronics).

One thing that you may have omitted from your plan is home switches and/or limit switches (and possibly also a tool probe) located at the router table, which would need to be wired up to your breakout board. You should use shielded cable for those connections to minimize noise pickup.

You might also have other cables, such as an emergency power off circuit and a router/spindle speed and on/off control.

[Al_The_Man]

Another very important conductor omitted, especially with that set up is a #14 or #12 gauge ground/bonding conductor.
Al.

[amishx64]

Originally Posted by doorknob I would prefer option #1 because ... I would also prefer to keep sharp edges on those pulses. ... which should minimize their exposure to noise pickup, and should also prevent the softening of the pulse edges.

Hmm I didn't think of this. Good point. Option #1 it is then!

Originally Posted by doorknob One thing that you may have omitted from your plan is home switches and/or limit switches (and possibly also a tool probe) located at the router table, which would need to be wired up to your breakout board. You should use shielded cable for those connections to minimize noise pickup. You might also have other cables, such as an emergency power off circuit and a router/spindle speed and on/off control.

I have planned for these other connections but I didn't include them in my simple diagram. The connections will be made using one or two lengths of SPT-shielded cat5e wire.

Originally Posted by Al_The_Man Another very important conductor omitted, especially with that set up is a #14 or #12 gauge ground/bonding conductor.

Al, do I need to directly ground my entire machine at the stepper motors or just the shielding running along the stepper wires? This is Earth ground, correct?

Thanks!