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home switches gone crazy
« on: March 03, 2009, 04:10:28 AM »
well I found a pretty wild problem and im not to sure why it happens but , I thought i would share so no one  had to go thru what i just did .  Well it all started out inocent enough I just wanted to neaten up my wire issues a bit,, so off to home depot i went to get some split wire loom.   I then  got back to the house and began what i thought was a very impressive looking  wire loom job all the wires tucked in there respective spots and not a single wire to trip over any more. So  I fire up my router to do a day of cutting and hit the home reference all button. and  not a one axis hits a switch  to home  ???..It just moves .100 or so and homes right there after about 10 hours of reading every  post about limit switches and swaping out cards  without any success.

I did the only thing left to do take all the wires back out of the wire looms to look for broken wires. I knew there where no broken wires because my home switches worked one the diagnostics page they lite up and worked fine the axises just would not go to them without homeing where they where first.  So after all the wires where out i just decided to try to home it again and in total amazment the router homed fine like it was supose to ??? So now im like huh to make a long story short when the motor wires are to close to the limit switch wires  you will get some kind of interference

Is there a special wire i should use right now im just useing  4 conductor telephone wire just on the limit switches I thought it was sheilded but maybee im wrong  any help would be greatfull   thanks
« Last Edit: March 03, 2009, 04:14:12 AM by ballistic31 »

Offline jimpinder

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Re: home switches gone crazy
« Reply #1 on: March 03, 2009, 04:28:00 AM »
I think you have answered your own question.

The four wire stepper motor drive wires are handling a heavy current for a split second and so produces masses of what is in effect magnatism. If you then pass a copper wire through a magnetic field, you get an electric current, so, in effect laying the wires neatly side by side, you are exposing your switching circuits to all the interference that your stepper drivers can muster.

My stepper driver wires are flat, heavy duty copper loudspeaker cable, which comes in a four wire strip. These are looped to the three motors, and becasue it is heavy duty, designed for rough usage, it just lays along the bottom of my machine tray.

The switches all route through shielded multicore cable, but again, I do no mix those with quick pulsing detectors (index wheel etc) with my limits and home, which are essentially slow on/off.

You might find, however, that if you increase your debounce timings you will get rid of a lot of interference, if you still want everything nice and neat.

Not me driving the engine - I'm better looking.
Re: home switches gone crazy
« Reply #2 on: March 03, 2009, 05:04:26 AM »
Thank you  jim  and very interesting input as well im  new to all the servo motor and  electronics, so i have been finding all kinds of  do  and donts thankfully the have  not cost me  alot of money yet, knock on wood   ;D. I dont have many wires to clean up so far just  three home switches and three motors so im sure i can find ways around this without to much trouble.  I am right now in the process of makeing the final  router project. I am useig this one  I built to build the  big bad  scary one ;D

I must say for this first build i can machine  aluminum .100 debth of cut at 20 ipm with a good finish and even thread mill at 20,000 rpms 8-32 holes with helical thread mills.  I was a bit leary at first being a machinist for 15 years in my mind no way was a machine made out of wood and plastic going to machine aluminum let alone steel. but somehow the little  guy does it .. well thank you again  for the great tips and advise, IM sure will come in  handy