Re: Testing homing limits resulted in motor stall errors with Mach1 #APCC

Dale Ghent

So, the primary cause of a motor stall is an external mechanical force that is countering the direction that the motors are driving the axes in question. Sometimes it's electrical, such as your power source (such as a battery) furnishing too little voltage to the mount.

Since you didn't mention verifying the physical condition of the mount and the stuff you have hanging off of it, have you checked balance of both RA and dec and looked for any cable wrapping or snags that could be catching and preventing one of the axes from turning past a certain point?

You assertion that the issue might be software-based is misinformed - APCC and the ASCOM driver sends commands to the mount controller to slew and move to the requested point; so the software on your computer is not responsible for actually driving the motors themselves every micrometer of the way. It's impossible for APCC to be directly responsible or the cause of a motor stall.

Describe your mount's load in more details and the work you have done to verify balance, as well as any other mechanical configuration issues that would be the most likely causes of a stall event.


On Jul 31, 2020, at 7:22 AM, Leo Shatz <> wrote:


Recently I had a very good remote session with Howard Hedlund from A-P, who helped me to setup meridian and homing limits. I did some tests following the session and I've got some issues I'd like to raise here:

Meridian flips were fine, I didn't run in any problems with flips going the wrong way, as long as the red telrad circle was staying within meridian limits. However, I had motor stall event triggered a couple of times in the following situations:

- I've defined an action of "stop tracking and slewing and park in place" in homing limits and let the mount perform unsafe pier flip. When it hit the homing limit (well before colliding with the pier), the mount stopped, the message saying that limit was reached and dialog box flushing. Few moments after that, since SGP was configured to perform parking on its own, it tried to perform parking but failed as mount was already parked. I've seen a yellow flashing sign in APCC indicating an error and there was freshly triggered "motor stall" event.

- I did the slow slew (at rate x200) to move CWs up higher until it reached the homing limits, the mount stopped again with a message from APCC and there was another motor stall event.

After both cases I was able to unpark the mount and perform slewing in both axis (without manually turning power off/on to the mount).

I'm afraid to repeat these tests as there could be potential problems with the hardware, although it looks to me more like a software glitch under these circumstances. I hope it's not actually caused by a physical issue with the mount, but possibly a software issue where there is some race condition in detecting abrupt change in motor speed and control signal stopping the slewing/tracking at horizon limit.

Leo Shatz

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