Home/Limit switch Cable HELP!!!

[planekrazie]

Hey Guys,
I am looking for 8 conductor 22awg twisted pair cable for my home and limit switches so I can run the cable in my cable carrier. Where in the world can I find this. It can even be 4 conductor. I tried to use 2 conductor non twisted going through the cable carrier with the steppers. Man what a mistake. I kept getting a " Limit switch triggered" in mach3. Took the cable out of the carrier and threw them across the table and they worked like a charm. HELP PLEASE,,
Steve

[tauntdesigns]

I had got some 6-con shielded from action, but it seems they don't have any right now. All they show in shielded wire is 2-con.
But they have 3,4,5, and 10-con non-shielded wire.

http://www.action-electronics.com/wirecable.htm

[jalessi]

Hi,

If you go to your local computer store and ask for a cat5 or cat6 patch cable (length of your choice) you will have a four pair twisted cable in your possession.

The super cheap ones might be solid conductor verses stranded wire, you can tell by its flexibility.

Hope this helps,

Jeff Alessi

[barbque]

Are you using Mach? If so make sure you have your Debounce interval/Index Debounce set. Its on the general config page. If its in a cable carrier with other siginal cables like drive and AC power it can pick up noise and trip your limit switches. I set mine to somthing like 1000-1500 to keep it from tripping.

[planekrazie]

You Guys are my heros!!!! Thanks
Ill reply with the results.
Steve

[mhasting2004]

Just a quick note.

Twisted cable will not stop noise getting into the line. The idea is that both lines will have the same noise and if the inputs are differential this noise gets ignored. Cat5 cable is not shielded.
Not sure exactly how you are hooked up but the best ways around noise are either:

Run higher voltages (like 24vdc prox sensors)
Run differential line driver signals
Run current loop

BTW if you do run shielded cable only ground the shield at the power supply end.

TTL 5 Vdc thru a micro switch is going to be very prone to noise if motor cables are anywhere near it

Just my $0.02 worth

Cheers

Mark

[jeffmorris]

Mark, Do you mean to ground the shielded cables at the power supply where the ground wire that comes from the AC cord is connected?

[mhasting2004]

Hi Jeff

Yes. Basically you don't want to create "ground loops" where current can flow from your power supply end, out to the signal end (limit switch in this case) and back via the shield or vice versa.

A common chassis and/or signal ground at one location is the aim (note sometimes signal ground is not connected to chassis ground (ie its floating) but each ground should still have its own common connection point). This is usually done inside your control / power supply cabinet on a terminal strip.

Stepper motor drive signals are very noisy due to the high current transiants. Putting is a small capacitor (say 0.1 uF) across any signal lines to ground can usually kill these spikes but it will also slow the response on the signal somewhat (may or maynot be an issue).

Cheers

Mark

btw chassis ground is the one from you AC input and stops you getting fried if something makes your machine "live". Signal ground is the low referance point for signals and may or may not be at the same potential of chassis depending on ones design. Ie opto isolation seperates the ground.

[jeffmorris]

Mark, I have Probotix PBX-RF board that has opto isolation. The shielded cable has a bare wire that's supposed to be connected to ground but which ground? The board has terminals marked "GND" in a few places.

[mhasting2004]

Hi Jeff

If it were me I would say the terminal closest to where the power (and ground) are supplied to the board. Alternately to a single post off the board with its own connection to the power supply ground.

Cheers

Mark

[planekrazie]

Lots of information here. Thank guys. Maby if I get this weekend off I am gonna re-run the limit/home switches. I picked up a few .01uF caps also Gonna try them too.
Steve

[stevespo]

I know this is an old thread, but did you ever get your limit switches sorted out? I'm fighting with the same thing right now.

Thanks,

Steve