LS7366R encoder counter issues

2

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  • Random thoughts...
    Only one end of a shielded cable is typically grounded to avoid ground loops. The AC neutral is eventually tied to earth-ground at the star-point of the transformer and then you have the machine's PE (protective earth)....possibility of ground loop?
    Failure is not an option...it's bundled with the software.
  • T ChapT Chap Posts: 4,000
    edited 2019-05-05 - 17:03:09
    In my case I never have shield connected at both ends.

    I do not have Neutral connected to GND at the power supply. Neutral connects to the - side of the transformer. I can easily tie them together, but it's odd this has never presented an issue and is only blowing up the LS7366. But if it's best practice to tie neutral and GND at the power supply that is easy to do.
  • Ah, sorry, miscommunication...I wasn't suggesting that you'd grounded both ends of your shielded cables, that was meant as an example of standard practice to avoid ground loops. For me, the 12v supply is the prime suspect here. :nerd:
    Failure is not an option...it's bundled with the software.
  • Can't tell from the pictures, is there anything in your circuit to prevent reverse current flow when the supply changes over during power fail and restore? (Assuming the whole chip is killed and not just a / some pins) As to the extra counts first mentioned, random noise might give different values each time. Are the quadrature signals filtered at the input to eliminate any power line or motor switching noise picked up in the 10' signal cables prior to the 7336 input pins?

    Oh, does this happen on one or multiple sites? Residential (US) systems require exactly one ground/neutral bonding point in the main panel. Not sure what your sites are like, maybe one is different from another or your bench system.
    Ordnung ist das halbe Leben
    I gave up on that half long ago.........
  • Filtering: The LS7366 only considers a pulse to be valid after so many clocks....I believe it's 3 clocks(?).

    Failure is not an option...it's bundled with the software.
  • Headed out to LA now to see the system that broke. Taking a logic analyzer so I can get a count from the analyzer and compare with the counter and see what’s going on.

    Frank, the encoder and counter only run on battery. There is no change over. Random noise should not accumulate in one direction only but somehow it is.
  • Is there any difference in load(current demand) from one direction to the other?
    Failure is not an option...it's bundled with the software.
  • T ChapT Chap Posts: 4,000
    edited 2019-05-06 - 14:22:32
    No. The motor is turned off while they are testing by hand. Freewheel. Clutch disengaged from motor. No noise from motor or clutch PWM.
  • Ok, missed the battery only for the click and encoder. Went back to your drawing. Noticed the prop and the click board are both on phs A and B of the encoder. If the prop still tracks the encoder, does its count agree with the click board or could the prop be doing something with these pins that would appear as pulses to the click?
    Ordnung ist das halbe Leben
    I gave up on that half long ago.........
  • Prop is not connected to encoder a/b. Only a MAX 7311 IO expander connected to Prop. No counting. Helps to be able to diagnose if pins toggle to trouble shoot all inputs in field.
  • T Chap wrote: »
    No. The motor is turned off while they are testing by hand. Freewheel. Clutch disengaged from motor. No noise from motor or clutch PWM.

    Holy moly, they can make it happen with no power to the motor. Presumably this means that it's not a long term drift and that you could disconnect the charger altogether and do the same test.
    Failure is not an option...it's bundled with the software.
  • jmgjmg Posts: 13,907
    Mickster wrote: »
    T Chap wrote: »
    No. The motor is turned off while they are testing by hand. Freewheel. Clutch disengaged from motor. No noise from motor or clutch PWM.

    Holy moly, they can make it happen with no power to the motor. Presumably this means that it's not a long term drift and that you could disconnect the charger altogether and do the same test.

    I've got lost here, is this now a replaced Encoder, or are these tests on the suspected damaged unit ?
  • Nothing is replaced. About to test with new counter module.
  • It seems that the 7366 is gaining/losing counts when the shaft is hand-rotated.

    I believe that the 12v charger is not suited for this application because its -ve is tied to the AC neutral.... just feels wrong.

    Coincidental with adding the 7366 is the addition of this charger.

    The fact that other components haven't been damaged, well that's nothing that we haven't seen before.

    Motor power issues have just been ruled out.

    If they can lose/gain counts by hand rotating, then the battery alone should be able to prove the point.
    Failure is not an option...it's bundled with the software.
  • T ChapT Chap Posts: 4,000
    edited 2019-05-06 - 21:56:45
    Update. Replaced counter and still accumulating ! Replacing encoder. The 5 dead 7366 were a different issue from this apparently.
  • jmgjmg Posts: 13,907
    T Chap wrote: »
    Update. Replaced counter and still accumulating ! Replacing encoder. The 5 dead 7366 were a different issue from this apparently.

    Has this unbalance/creep issue always been there, or is this new ? (after some stress event ?)
  • Common denominator?
    Failure is not an option...it's bundled with the software.
  • Replacing the encoder? Lose the charger.
    Failure is not an option...it's bundled with the software.
  • T ChapT Chap Posts: 4,000
    edited 2019-05-06 - 22:50:42
    Replaced encoder. Cables. Interface BoB. No motor connected. No charger. Still accumulating.
  • jmgjmg Posts: 13,907
    T Chap wrote: »
    Replaced encoder. Cables. Interface BoB. No motor connected. No charger. Still accumulating.

    by appx how much, and is it the same each time ? eg if you attach vice grips or similar to get a known up/down span, is it consistent.

    In theory any noise impulse on quad encoders should self-cancel, with an inc/dec pair, but maybe their filters are not perfectly symmetric ?
  • Nice 5v pulses from the encoder?
    This is quite bizarre.
    Failure is not an option...it's bundled with the software.
  • Filters should not even be an issue...10' cable run and no PWM noise?
    Failure is not an option...it's bundled with the software.
  • Here is the installed shaft encoder. Obviously some issues here.
  • jmgjmg Posts: 13,907
    T Chap wrote: »
    Here is the installed shaft encoder. Obviously some issues here.

    What that a mechanical pause (tho the rate seems stable?)
    If it is not at a pause, that's unexpected, but those lone pulses should cancel, with a ++/-- pair ?
  • I think this is solved. The shaft encoder is bad. As shown. The other encoder test (mounted on rear of motor) that tested to accumulate as well really wasn’t. I like to run the Clutch at 50% when idle and I was slamming the motor back and forth against a hard stop by hand causing the clutch to slip when the motor came to an abrupt stop. I set the clutch to 100 and now the motor mounted encoder is consistent. Thanks guys for the suggestions! This particular issue is handled. Who knows about the bench issues.
  • frank freedmanfrank freedman Posts: 1,495
    edited 2019-05-07 - 05:03:18
    Just curious, but does your design have a software or hardware limit switch for an e-stop function to avoid hitting an end stop? Guess virtual troubleshooting, kibitzing or whatever makes good mental excercise. Besides, it's the suburban substitute for the old sidewalk supervisors seen looking through cutouts in the fence around hi-rise projects.......
    Ordnung ist das halbe Leben
    I gave up on that half long ago.........
  • MicksterMickster Posts: 1,449
    edited 2019-05-07 - 10:20:55
    I guess I'm still baffled by how the one channel quits generating pulses.

    Edit: Oh wait, that's the "bad" encoder.
    Failure is not an option...it's bundled with the software.
  • Can't remember the last time I had an encoder failure so do we surmise that whatever was causing the LS7366 to fail has also damaged the encoder?
    Failure is not an option...it's bundled with the software.
  • jmg wrote: »
    T Chap wrote: »
    Here is the installed shaft encoder. Obviously some issues here.

    What that a mechanical pause (tho the rate seems stable?)
    If it is not at a pause, that's unexpected, but those lone pulses should cancel, with a ++/-- pair ?

    The pulses only happen during shaft rotation. A pause would be two flat lines at whatever state. The two streams are 90 degrees out of phase (count/direction).

    That particular condition of one channel flat-lining can happen when you have a fractured conductor in a moving conduit/cable chain. You get a make/break during movement of the axis.
    Failure is not an option...it's bundled with the software.
  • Is that a normal mark-space ratio, BTW?
    Failure is not an option...it's bundled with the software.
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