Welcome, Guest. Please login or register.

Username: Password:

Author Topic: Motors only move in bursts of 3 steps.  (Read 25 times)

PaulEvans

  • Full Member
  • ***
  • Posts: 11
    • View Profile
Motors only move in bursts of 3 steps.
« on: May 22, 2019, 12:20:50 »

Hi. I am trying to sort out a particularly annoying Dec guiding issue. I have an EQ5 with belt drive and NEMA14 stepper motors, and have entered my config in AstroEQ. The mount slews fine, and guided by PHD2 it tracks well in RA with RMS values of below 1arcsec. However my Dec tracking is all over the place, the guidelogs show PHD2 applying repeated moves of 2-15 msecs, nothing happens for ages and then there is a massive sudden overshoot.
In trying to diagnose it today in daylight by "manual guiding" in PHD2, I have noticed that both in normal RA sidereal tracking, and in Dec manual guiding, there are groups of 3 pulses (sounds like a rapid ratttle) going to both RA and Dec stepper motors. So RA sidereal tracking is proceeding in a series of small jerks, I would expect single evenly spaced pulses.
Equally when I apply 100msec Dec moves from PHD2 manual guiding, I get no reaction for 3-4 presses of the N or S button, and then a rattle of 3 steps. This and the fact that my Dec guiding is jerky may not be unconnected....
I'm thinking I must have messed up a parameter somewhere, but I'm damned if I can work out which one.
Any and all advice appreciated!

Paul Evans 
Logged

PaulEvans

  • Full Member
  • ***
  • Posts: 11
    • View Profile
Re: Motors only move in bursts of 3 steps.
« Reply #1 on: May 25, 2019, 07:12:18 »

And to add some further detail, I have the AstroEQ set to 1/16th microstepping, and I think that it is microsteps that are happening in groups of 3, not full steps. I'm going to do some further experimentation, including checking the current limits and trying out 1/32nd microsteps. The motors are NEMA14 with a current limit of 0.8A per phase.
I bought the AstroEQ ready assembled. I'm using config utility 3.8.3 and firmware 8.11 so I'm also going to try upgrading. EQASCOM is v2.00K and I see that 2.00Q is currently available. I'm on latest PHD2 - v2.6.6.
Logged

PaulEvans

  • Full Member
  • ***
  • Posts: 11
    • View Profile
Re: Motors only move in bursts of 3 steps.
« Reply #2 on: May 28, 2019, 12:14:39 »

Ok in case it helps anyone else, progress to date has shown 2 problems -
1. One of the original 8825 boards (the RA one) had burnt out some time ago (disconnected RJ11 lead under load, doh...) so at that time I replaced it with a clone which is not as easy to set the current limit on. As part of recent investigations I've just installed a proper Polulu 8225.
2.  With 2 proper driver boards installed I could then set the motor current using the accurate not the rough method for RA and Dec. Both were significantly too high, are now OK, and both motors now respond much better to microstepping. I'm now quite keen to get a clear night and see if the finer control of motor microsteps translates to better Dec tracking.
I will update this thread if I learn any more, but for anyone struggling with diagnosing a fine motor movement problem, the "manual guiding" NSEW pad in PHD2 allows FAR finer control of motor moves than the one in EQMOD.
Logged