Re: encoder readings problem

[Babar <riet91-at-yahoo.com>]

 I will second Jon and Les , The problem seems to be
due to some sort of noise, which you can encounter
having differential outputs of encoder.

Babar 
--- Jon Elson <elson-at-pico-systems.com> wrote:
> 
> 
> 
> nasir2ahmed-at-yahoo.com wrote:
> 
> > we are using the stg model 1 card for emc software
> to control our 
> > lathe machine
> >
> > we are having trouble to successfully run stg with
> emc.the problem we 
> > are facing is that our position counter starts
> very fast readings and 
> > it continous flow even  we estop the whole system
> and emc software, it 
> > continouslly flow and give the highest
> >
> > out put voltages at DAC. this problem is only
> coming in our Y-axis. 
> > and because of this problem our machine had three
> seviour acciedent. 
> > this problem can come at any time not
> continouslly.
> >
> > and when  we restart our emc software the machine
> will work correctlly.
> >
> > is this the problem of pid settings? or this
> problem is directlly 
> > related with any out side distortion.
> >
> I'm not clear on what is happening.  When this
> happens, the position 
> count is changing
> even when in E-stop, and there is nothing moving? 
> Is that correct?
> If so, you have either a defective encoder, encoder
> cable or STG card.
> The PID parameters won't have any effect on this. 
> To prevent accidents,
> you should have the error tolerances set to a small
> value, so the machine
> estops quickly when the encoder error happens.
> 
> If you can trigger the problem by moving the machine
> in some way, 
> tapping on things, jiggling
> cables, or whatever, try swapping the encoders to a
> different axis input 
> on the STG
> card.  Then you should be able to find out whether
> it is the encoder or 
> the STG card.
> 
> If you mean that the machine continues to move after
> estop, then your estop
> circuit is not working.  You MUST, for safety, have
> an all-hardware estop
> circuit that removes power from the servo amps.
> 
> Jon
> 
> 


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