View Full Version : The worst way of wiring . . . . .

Gerald D
Tue 22 April 2008, 08:53
Although the impression is that this is neat and tidy wiring . . . .


. . . . . . it is the worst way that wiring can be done for our control boxes.

Power supply, signal, and motor wires are all:

- unscreened

- run parallel to each other

- are tightly strapped to each other

There is a huge potential of interference from the higher current wires getting into the signal wires.

Tue 22 April 2008, 09:13
I think wood is bad also for mounting everything to. Not only fire hazard it looks kinda cheap IMHO. Why spend 5K on a nice machine and have a wood control board. I guess if a person just had to have a wood control board it would be quilted maple or black corina or maybe flammed Koa....something nicer looking anyway.

Hard to see from that photo but it looks like the aluminum plates that the drivers are on, are tight against the wood so that no air flow or heat dissapation is going to happen. (why even use the alum. if you do that?)

Hopefully that is just the kitchen project test board that someone tried to do a very neat job on.:D

Mon 13 October 2008, 00:23
Geralds comments are quite valid, but he forgot to give some suggestions to correct the problems. The signal and power wires need to be as far apart as possible. When the signal and power must be close together (when connecting to the Gecko Drives ), keep the parallel runs as short as possible. If you must cross the power and signal lines, try to make the crossing as close to 90 degrees as you can. Using these tips will keep interferance to a minimum.

Hope this helps.

Gerald D
Sun 23 November 2008, 08:48
This thread needs a reminding bump.

I notice that some folk are hiding wires in plastic conduit, but the same principles apply. Bunching unscreened signal wires together with power wires is a bad idea.

Marc Shlaes
Sun 23 November 2008, 11:38
I have been meaning to ask this and this reminder makes it a good time. Most people, if not all, are running the power wire for their router in the same cable chain. Is the fact that each of the motor wires are screened / shielded in their separate casings what keeps this interference problem from occurring outside the control box as well?

Gerald D
Sun 23 November 2008, 12:58
Well, the router wire should be a shielded cable where it runs parallel to all the other cables in the chains, etc. Don't assume that the power cord supplied with the router is a good cord for CNC - shorten that cord and replace with shielded cable.

The reason for shielding the router wires is because they become transmitters of noise (especially when the router brushes go bad). Best to stop that transmitted noise at source by shielding the antenna (the long wires) of that transmitter.

The stepper motor cables are shielded for the same reason as the router. Being potential transmitters, that will radiate noise. (not because of bad brushes (they have none), but because of the high step pulse frequency)

Noise radiation (by router or stepper motor) becomes a problem if there is a receiver that is going to pick it up. Our receiver in this case is the bob that sends signals backwards and forwards to the PC. Those long wires from the bob to the limit switches or pushbuttons, or the short wires from the bob to the geckos, are the antenna wires that could receive the interference. So we go for belt & braces by shielding our receivers and transmitters.

Marc Shlaes
Sun 23 November 2008, 15:21
But... but... but...

That cord that runs through the chains is 25 feet long. Can you even buy shielded "tool cord" wire to replace it with? Anyone? I don't think I have ever even seen it.

Sun 23 November 2008, 18:42

Are you talking about using shielded wire to power the router? The cable I used is shielded.

Gerald D
Sun 23 November 2008, 20:58
I thought we covered it in: Screened flexible cables (wires) - specifications & sources (suppliers) (http://www.mechmate.com/forums/showthread.php?t=2) ?

The 1070**** series drawings also show screened router cables.