New Machine Build- Electric noise - home/limit switch

[feragto]

Hi , I conected today my first home made CNC router . But in phase of testing I notice that my home-limit switches on set-diagnostic screen of MACH 3 very quickly turn on and turn of , not regulary ant not in some kind of order . I assume this is a electric noise ?! I try all disconected ald connected but without succes . Programimg part is not a problem , I do all what I need in MACH 3 . Can somebody help me with a few suggestions ?
Thanks .

[Dorsal]

Are you using shielded wires for those home and limit switches? Is the shield connected to ground at the controller card end only?

[johnmac]

Go to the general config page and change the entry for the debounce. Since you can see the switches tripping, you may need a setting of 7000 - 9000.

John

[Realmseeker]

I have the same problem sometimes as the first poster. I tried setting debounce to 1000-2000. The problem I have is that if I set it any higher, after my limit switches make contact when homing, my gantry moves way off the limit.

I to do not have shielded wiring for my limit switches, and most likely really need to consider the upgrade. I have a small problem that during a program run, my machine gets a false positive on the limit switches. But this only happens if I have my spindle running, and not during a test cut when just cutting air.

[JD_Mortal]

I am not sure what you are using for your switch, but I can list a couple of things that may be wrong...

If this is a physical switch connection, there is no such thing as "noise" in an open-wire connection. However, if you are plugging this into a "circuit IC" to detect open/close state, and you have poor grounding, and the IC is RF sensitive... You have a ground-loop issue. Check your grounds and shielding, and any noisy-RF device that is too close to your detection circuits.

If your switch is cheap, it may have poor spring-tension keeping the switch open/closed. Switches have g-force ratings, get a switch with better g-force ratings to stop from being physically vibrated on-off.

If your switch has micro-contacts, with a micro-gap, but your switch-voltage is too high... It is arcing, or the plates are becoming a mini-capacitor and releasing built-up electrons once it fills or vibrates a micron closer.

Try a physical debounce on the switch... Though, it is not a debounce issue. (A high-ohm resistor 5M and a 0.001uF capacitor. Should keep a slight low voltage, and absorb high RF noise, keeping a low-state presence. As opposed to being an open-IC path which senses cross-talk from the chip and RF noise in the line. Going from 0v to 5v is not what an IC expects, it expects ~<1.5v low to ~5.0v high, for example.)

Try an RF choke and shielded wires. (Shielding must be hooked-up to ground, otherwise it is just more capacitance and RF antenna structures.)

Get a new LPT port/cable/computer. LPT chips, and older computers are horrible. They self-collapse and become electrical "ghosts in the machine", which is why everyone abandoned old computers and LPT ports in the first place.

[Fastest1]

Originally Posted by JD_Mortal Get a new LPT port/cable/computer. LPT chips, and older computers are horrible. They self-collapse and become electrical "ghosts in the machine", which is why everyone abandoned old computers and LPT ports in the first place.

Not all of us have issues with the PP's. Nor has EVERYONE abandoned them. Maybe the big machine shops dont use them anymore but the home shops are alive and well on PP computers. He also states the diagnostics page is showing a light flickering whether the limits are connected or not. Does it flicker if you disable the limit switches? I know it shouldnt but you have to exhaust all possibilities. Is the machine or its frame physically touching the controller and or computer or its case?

[feragto]

Originally Posted by Fastest1 Not all of us have issues with the PP's. Nor has EVERYONE abandoned them. Maybe the big machine shops dont use them anymore but the home shops are alive and well on PP computers. He also states the diagnostics page is showing a light flickering whether the limits are connected or not. Does it flicker if you disable the limit switches? I know it shouldnt but you have to exhaust all possibilities. Is the machine or its frame physically touching the controller and or computer or its case?

Yes , the light go on and also disable electronic (same as I press the switch) . No , there is not any contacts between machine and electronic case or computer . I have electronic from CNC Stepper Motor Driver Systems & Hobby CNC Routers:: PROBOTIX™ .

[hemsworthlad]

This is very common and easily fixed by doing what Johnmac suggested and setting the debounce in mach or if real bad then using a small capacitor.

Usually the debounce will solve the issue straight away and i think it will in your case as well.

There wont be anything wrong with your PP or computer so ignore JDMortals biased comment over PP's he's obviously wrong because just about every DIY CNC ever built use's the PP (Except me I use Smooth stepper, but for other reasons.!)

Good luck.

[feragto]

Originally Posted by hemsworthlad This is very common and easily fixed by doing what Johnmac suggested and setting the debounce in mach or if real bad then using a small capacitor. Usually the debounce will solve the issue straight away and i think it will in your case as well. There wont be anything wrong with your PP or computer so ignore JDMortals biased comment over PP's he's obviously wrong because just about every DIY CNC ever built use's the PP (Except me I use Smooth stepper, but for other reasons.!) Good luck.

Can you point me in direction to mount a small capacitor ("normal" or "electrolitic +,- ") , how big ...nF , uF ..., and where to mount . Thanks in advance for your help .

[feragto]

Hi ,
I am notice that my debounce interval and index debounce is booth zero (o) . Because I have electric dust in my home- limit switches , can somebody help me and tell which value need a write instead of zero , mybe this will solve my problem . My MACH 3 running on 35.000 Hz.
Thank you in advance for help .

[brtech]

try 1000 first. You can go up to 7 or 8,000 if you need to.

For a capacitor, I think .1ufd would be adequate.

[feragto]

Originally Posted by brtech try 1000 first. You can go up to 7 or 8,000 if you need to. For a capacitor, I think .1ufd would be adequate.

I this value the same for booth debounse and index , or only for debounse and the indes value is zero ? Capacitor wired series or paralel ?