Roast my wiring

[Mr.Hotwire]

I have been waiting up my control box. I'm about to start with the sensors, and I want to get some critiques before I get too far into it. I mean... I guess I'm pretty far into it now...

I will be putting a circuit breaker on the DIN rail (once I can find a 110v 20a), and a master power switch on the door. There will also be indicator lights, and an e-stop button installed remotely.

[Robertspark]

it's not recommended to daisy chain stepper motor drives, they are best fed with their own power cables directly from the power supply.

https://www.geckodrive.com/support/step ... asics.html

the drives are a bit close together

the drives may be in the wrong orientation, if the panel is installed vertically and they are going to be horizontal as the airflow won't convect past the fins on the heatsinks and get a chance to dissipate the heat.

I presume in your locality neutral is the same as earth / ground and you don't have a 3 wire power supply (live / hot wire, neutral and earth / ground)?

[spumco]

Ditto what Robert wrote about the drive orientation: mount them vertical.

I think the 'daisy chaining' is for the 0V on the signal side of the stepper drives, yes? Not the HV-DC side - I see separate wires/cables between each PS and drive pair...

***EDIT*** looking again at your photo... looks like you've connected two drives per power supply on the power side with a single cable that has a "Y" in it. I think Robert's right on this one too... use separate cables for each drive. If the PS's can handle the amps - fine - but you should have four wires coming off each PS per drive pair). So now I'm wondering what the 3rd PS is for?

Here's my suggestions:

1. If you get noise, missed steps, or other drive control issues: replace those (admitedly very tidy) sheathed heavy cables with shielded twisted pair cables. The signal cables from the AXBB can be really tiny - like 26AWG - with no problems; they only handle milliamps. Shielded 24-26AWG CAT5 cable is great for this (smaller is just a pain to work with). Use one pair (per cable) for STP+/STP-, and another pair for DIR+/DIR-. Tie the STP/DIR- together back at the drive and connect to 0V per the CNCDrive diagram. Heat-shrink a pigtail of the shielding at the AXBB-E end, crimp on a ring terminal, and connect the shield pigtail to the backplane or AXBB-E mounting screw. The AXBB-E doesn't have true differential I/O, but this will get you close and eliminate step signal noise (if you find phantom missed steps).

2. You appear not to have a contactor or other method of killing power other than your future 'master power switch'. This means your 'ESTOP' circuit design will not be capable of disconnecting power to the drive power supplies. It will just be an ESTOP signal to UCCNC/AXBB-E. That's fine for a home-brew system, but what if Windows locks up? You have to fumble for the master switch.

My preference is to have a master switch that supplies power to 1) the control power supply (for the AXBB-E), and to 2) a contactor, with a main breaker upstream. Close the master switch and the AXBB-E powers up, but the contactor stays open (no power) until you energize it. The contactor coil side is controlled by your ESTOP system.

If you want to get fancy, a low-voltage (24vdc) holding relay activates the contactor coil so that when you unlatch the ESTOP button you have to press a momentary RESET push button before the contactor engages. Doing this opens other options... like having the AXBB-E and UCCNC being able to command an ESTOP event, but the control is unable to undo an ESTOP without human intervention (reset button). If you tie the holding relay coil to an AXBB-E output then the machine/system can't energize the drives until both you and UCCNC are happy with the situation.

The other benefit is that your E-stop and reset buttons are low-voltage DC - safer for the operator.

3. Get a cooling fan in there; move the DIN rail if you have to. Fan at the bottom left, exhaust at the top right (or vice-versa). Run the fan off the control DC power supply so it's on all the time (helps you to hear if you've left the machine on).

4. The little relay board is kind of buried behind the power supply AC wires. Maybe move it so you can get to the board & connections a bit easier.

5. What else is going in there? I see drives and a controller... but what is the machine? Do you have a VFD or other spindle, or is this for a plasma or laser?

6. Signal wires... don't bother with bulkhead connectors like you did for the drives. Just use gland seals and pass the signal cables directly through to the AXBB-E. Saves wiring, eliminates potential connector issues.

Here's a slightly more complicated UCCNC installation I did recently. Not finished in this photo, but it's done now. Is 5'x10' combination plasma/router.

-Ralph