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Author Topic: Problem getting clean index pulse  (Read 4247 times)

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Offline mick

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Problem getting clean index pulse
« on: March 22, 2009, 02:14:22 PM »
Hello all,
           My lathe is servo driven,for the past six months useing the p/p, all was well until three days ago i connected a s/stepper i've
           had for about nine months.
           The problem is the index pulse is all to cock now,looking at the trace in spindle/config where there used to be square wave,
           now it shows confused spikes about three times higher than the square wave,swapping back to the p/p every thing ok.
           
           Can you please help cure this problem as threading is impossible.
   
           Useing the latest Mach3 & s/s plugin.
                                                                   thanks mick. 

Offline Repmo

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Re: Problem getting clean index pulse
« Reply #1 on: April 25, 2009, 10:32:53 AM »
Ground problem ??

On SS,  the 2 port had independent ground...
you can add optocoupler, that reduce noise.....

Offline mick

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Re: Problem getting clean index pulse
« Reply #2 on: April 25, 2009, 02:28:26 PM »
Repmo,
          Thanks for coming back.
       
          The index problem was solved with a new BOB, but after a 20 minute test run using s/stepper
           both z & x axis return to -.025" from zero on DTI,
 
           The same test using p/port both axis return to .001" from zero on DTI,

           Even after removing the s/stepper from the enclosure & trying to screen in metal case, the result was same.

           all encoder lines are screened twisted pairs, step & dir are also screened.
           So for now iv'e gone back to using p/port until i can face re-wiring the whole thing.

                                                                                                            rgds mick.

Offline Jeff_Birt

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Re: Problem getting clean index pulse
« Reply #3 on: April 25, 2009, 04:19:26 PM »
Is your BOB opto-isolated?? I would suspect not. I always recommend opto-isolating the I/O to/from your controls. If you don't you will always have problems. With an LPT driven machine the problems will still be there but they show up as 'Mach did something weird today!). With the SmoothStepper the noise problem will jump right out at you and smack you in the nose and say, "This machine is noisy!".

This is one of the reaons I like the new Gecko G540. Opto-isolation is built right in.
Happy machining , Jeff Birt
 

Offline mick

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Re: Problem getting clean index pulse
« Reply #4 on: April 26, 2009, 04:47:47 AM »
Jeff,
      the BOB inputs are opto-isolated,the outputs are buffered.

      if i fit opto's to the output, would it be best to fit them close to the drives or close to the BOB?
                                                                                                                   thanks mick.

Offline Jeff_Birt

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Re: Problem getting clean index pulse
« Reply #5 on: April 26, 2009, 07:45:52 PM »
Let me make sure I follow. The inputs into the BOB from your limit switches, etc are isolated but the outputs from the BOB to your relays and drives are not? Some drives have optos built in to the S/D signals (like Geckos). Some do not. If your drives and other outputs are not somehow isolated then having the inputs isolated is useless. What make/model is you BOB?
Happy machining , Jeff Birt