Re: [CAD_CAM_EDM_DRO] Limit Switch Cable Noise

In a message dated 10/28/2006 4:43:09 P.M. Eastern Daylight Time,
salhab@... writes:

Hi all,
I've been installing mechanical limit switches on my mill I've used
shielded cables(about 10 feet) and ground them and set the switch on
the normal close and Mach2 pin setup on Active High , every thing
reads well , but once I turn Motor Power on limit switch trigger
starts flashing very fast causing Mach2 to stop I think it is noise
problem.

I've read in Mach2 Manual in chapter 4.6.1 (Limit Switch Strategies)
that I have to use 5VDC power supply with 470 ohm resistance parralel
with mach2 pin (Fig 4.7).

Does this solve my problem or should I look for a breakout board ?

Thank,
Shadi Salhab



Shadi:

Did I read your post correctly, you are putting a 470 ohm resistor in
parallel with the input pin for you Mach2? I take that to mean you have a 470 ohm
resistor across the contacts of your limit switches. If that is true, it
isn't logical as you would NEVER end up with a completely open circuit across
the switch, now, if the resistor is being used as a pull up or pull down
resistor, that would be logical and 470 ohms is one of the normal values used for
that purpose. Did you use twisted pair cable? It works much better than just
normal shielded cable. Did you connect both ends of the shield to ground?
Normally you connect only ONE end of the shield to ground. From your
description it does sound like you are getting a lot of electrical noise when you
start the motor(s). In some cases, it may also be necessary to use shielded
wiring to the motors as well. Also, if the motor is AC you might need to put a
resistor/capacitor network "noise suppressors" across the power leads to the
motor. You also should put those noise suppressors across any AC coils that
are used in relays or motor starters. All of this will help in correcting
noise problems. If you can send me a little diagram of how you have your
switches connected directly to _cnc002@..._ (mailto:cnc002@...) , maybe I
can get a better picture and idea of what is happening.

Randy Abernathy
4626 Old Stilesboro Road NW
Acworth, GA 30101-4066
E-mail: cnc002@...

I furnish technical support, repair, and other related services for your
industrial woodworking machinery. My background as Senior Service Engineer for
the SCMI Group for nearly fifteen years with factory training, combines with
my extensive background in electronics, mechanics, pneumatics, electrical and
CNC machinery to offer you needed support for your machinery. Services
include but are not limited to the following:


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