Hello Guest it is August 08, 2020, 03:20:55 AM

Author Topic: phantom limit switch  (Read 10074 times)

0 Members and 1 Guest are viewing this topic.

Re: phantom limit switch
« Reply #20 on: March 11, 2008, 08:28:27 PM »
O.K. I had to do everything on the list and step 9 was last, and what it finally took. The motors are running great, BTW Geck suggest 20x phase voltage and thats puts us around 48v.

Now the Phantom limit switch is back though......

I set the debounce up to 2000 and seems to be OK for initial test.

Speed is satisfactory for me on motor tuning at 150 feed.

These is still an occasional spike in the driver test but nothing continuous like before, mostly flat..

There's a slight chop in the motor but I think I can tune it to a minimal with more time.

I'll call it success for now, unless you have any better ideas for the phantom limit. It's consistantly on the Y axis only. 

Offline Chip

*
  • *
  •  2,055 2,055
  • Gainesville Florida USA
    • View Profile
Re: phantom limit switch
« Reply #21 on: March 11, 2008, 09:16:28 PM »
Hi, Spiwrx

Sounds good, If Your Happy with the Speed, Lot's of figure's get bounced around on Stepper's

On the Y limit, Maybe a bad SW/Contacts, Some have put small .01 disk capacitors across the SW terminals, pull up or Pull down resistor's, Re-check the wiring, Swap the Switch's

around, or Let it work for a while,.

Are your SW's N.C. in Series  or N.O. in Parr.

If you have a O-Scope you should be able to track it down at some Point.

Have Some Fun Sounds Better, Chip
« Last Edit: March 11, 2008, 09:24:10 PM by Chip »
Re: phantom limit switch
« Reply #22 on: March 12, 2008, 12:26:39 PM »
Switches, are 2 per axis NC wired in series. They're new but something thats been laying around are warehouse for a decade or so...

Didn't quite understand your ref to the pull up / pull down resistor though.

I have a scope, but it's buried in my garage, antique tube type HP unit... (Lets hope we don't need to get that out)

Was going to use proximity switches but with the design of the machine being fairly open, I was concered with debris/chips setting of the proximity sensors

Offline Chip

*
  • *
  •  2,055 2,055
  • Gainesville Florida USA
    • View Profile
Re: phantom limit switch
« Reply #23 on: March 12, 2008, 02:47:54 PM »
Hi, Spiwrx

Doing  a little research hear on De-bounce, 1000 is 40ms. 10000 is 400ms. The time is the amount a switch has to be on to

be consider "on", Per Art, In lot's of posts set it to 2000-3000.

I would think that the 2000 isn't to bad, If you think the Y axis is causing the problem.

Install a jumper on one of the switches, Reduce the de-bounce and test, Then test the other switch.

The comment on,  pull up or Pull down resistor's there used on some TTL encoders to keep them from floating between Hi or Lo state

Thanks, Chip
Re: phantom limit switch
« Reply #24 on: March 19, 2008, 03:34:02 PM »
One Last thing ( I Know famous last words ) Anyway, everything previously seems to be cured. We switched to NO limit switches in parallel as well as replacing them all, also added sheilded cables to the limits, thought only the motors had to be.

Anyway, the current issue, and hopefully the last is on a Ref. All Home command, about 1 out of 3 times it engages a limit swicth stop as it's reversing out whichever axis homing (all three have this issue randomly however it's usually just one axis each time).

So it doesn't back away enough to release the switch before the limit switch takes over. I tried changing the speed, and debounce, neither seemed to help. Is there another setting I can tweak??

Offline Jeff_Birt

*
  •  1,107 1,107
    • View Profile
    • Soigeneris
Re: phantom limit switch
« Reply #25 on: March 19, 2008, 04:20:25 PM »
Quote
We switched to NO limit switches in parallel as

Normally open limit switches should really be avoided at all costs. When a limit switch fails or its lead is open it should fail safe (limit on). Normally open switches can't so this. I've seen $250,000 machine crash doing $10,000 of damage as they were made with NO limits.

I don't know what switches you are using but I have found that running limits at 24V through a opto-isolator with 5V on the other side of the opto for the controller provides very reliable operation.
Happy machining , Jeff Birt