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Messages - comet

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31
General Mach Discussion / Re: Long encoder cables can you help
« on: February 03, 2018, 03:53:23 PM »
Mad dog, thanks reading your post has made me realize what the problem is ......probably!
I am using a line driver , but I've placed it at the drive end not the encoder end.....doh!!
I'll rewire it tomorrow and see if that improves it.
Cheers all
Tony

32
General Mach Discussion / Re: Long encoder cables can you help
« on: February 03, 2018, 02:22:37 PM »
What makes a cable capacitive? That seems something that you have to be wary of.

33
General Mach Discussion / Re: Long encoder cables can you help
« on: February 03, 2018, 02:20:15 PM »
So if you have a single ended encoder how do you use twisted pairs, if you can't twist a&b together? Ultimately I suppose putting on differential encoders plus the associated cabeling is the answer but the expense is prohibitive in this case.

34
General Mach Discussion / Re: Long encoder cables can you help
« on: February 03, 2018, 11:50:21 AM »
Hi no they are single ended just a+ b+ .
Afik ?

35
General Mach Discussion / Long encoder cables can you help
« on: February 03, 2018, 09:28:35 AM »
Hi,
  The situation im in is with a retro fit on a customers Wadkin fabricated industrial router.It was fitted with a bosch pmdc system running at 150volts.
I have scrapped all of that system and saved the servos which I have fitted 360ppr chinese single ended encoders on the back (they had tachos on).
  I am using ucnc dg4s 180 drives and there uc 300 motion controller, all of which im happy with.
The ancillary power supplies have there 0 volts commoned to the computer 0 volts and then to machine  ground, but not commoned to the servo main power supply.
The servos have twisted power leads, the encoders have 4core 0.5mm with an overall shield which is grounded only at the drive end.
    Interestingly i can disconnect the grounds etc. and it makes no differance.

The issue :

 Z axis - runs perfectly really smooth encoder/motor leads approx 4 ft long.
 X axis - holds position on start up but if you touch the pulley or give it a command it judders like a crazy thing and creeps forward,uncontrolable and wont stop unless you reset drive. encoder/motor cables approx 12 foot long.
 Y axis - behaves  exactly as X again 10 foot encoder /motor cables.

I have tried swapping drives and motors around with no differance, so I have come to the conclusion its possibly cables, or at least the length of them.
  I have sopken to Balazs at CNC drive and got this answer:
"I think the jumping is caused by electrostatic charge, likely the body of the encoder is statically charged with the motor and maybe even the machine frame"

But im afraid he gave me no solution to it.
  I have read that putting 2 capacitors at the encoder power  end (0.1 +0.001 uf) can help filtering
Also using pull up or pull down resistors on the A B channels can help (will need some clarity here)
Or should I try to totally insulate the encoders from ground.?

I shall be going back on site tommorow to have another go at it, Any thoughts?

Regards
   Tony

36
General Mach Discussion / Re: I Need a macro written will pay.
« on: February 02, 2018, 09:50:26 AM »
wow thats great work, i shall be looking at this over the weekend, so watch this space !

37
General Mach Discussion / Re: I Need a macro written will pay.
« on: February 02, 2018, 04:25:05 AM »
Cheers Thomas I shall have a play with that later today on the bench.

38
General Mach Discussion / Re: I Need a macro written will pay.
« on: February 01, 2018, 10:03:09 PM »
Found the laser manual ive attached it

39
General Mach Discussion / Re: I Need a macro written will pay.
« on: February 01, 2018, 09:51:57 PM »
Ill have a look, but on reflection I dont think i want to be messing about with mach4 right now, as well as trying to get this project working, atleast if I dont have to.

40
General Mach Discussion / Re: I Need a macro written will pay.
« on: February 01, 2018, 07:12:12 PM »
Chaotcone , yes I would be but that is the sort of stuff that is presently beyond me, but hopefully not for others.Do you have a link?

Tony




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