First I would just hit the STOP button before resorting to pulling motor cables.
Second, if I were experimenting and was worried about DEC axis wrap-up and cable damage, I would just unlock (or at least loosen a bit) the clutches until I was done with my experimentations.
I hope that helps.
From: ap-gto@... [mailto:ap-gto@...]
Sent: Friday, January 30, 2015 7:21 AM
Subject: Re: [ap-gto] Verify parking sequence
I have one exception to your statement below – there are situations when the mount hasn’t got a clue where it is. Fortunately, the ASCOM driver lets us give the mount its Unpark position.
Yesterday, I upgraded the chip in a spare CP3 controller, and trusted that a PARK command would home-in on the nearest quadrant, so I could level the axes. Imagine my surprise that my Park-2 spun the RA & DEC axles 360 degrees ... and kept right on going. Fortunately the slew rate was set for only 300, so I could rush over to kill power after the DEC cable had already fully wrapped itself around the mount. I powered up again and another Park kept it moving ... again in the same direction. I unplugged the DEC cable and re-issued the Park-2 command and watched to see if the AP-900 controller would EVER come to a stop – it didn’t.
Next power cycling, I told ASCOM to Unpark “specifically” from PARK-2, which it seemed to. Then I issued an ASCOM driver PARK-2 command to see if it finally understood and would move “less than a quadrant” from its current position. This time, the mount finally found its way, and subsequently always parked correctly at any position I chose. So, a warning about what could happen after a chip swap, or some other unspecified situation.
Luckily, I had the mount in the house with no other attached cables except for the mount cables, which survived almost being snapped by the misguided mount. So, there are hopefully exceptionally rare times, when the servo loses all idea of its position, and can’t find its Parking home position, without a bit of human guidance.
Since it is the one most likely to wrap and snap, it would probably be wise to disconnect the DEC cable after doing a chip change, and test the mount’s first attempt at parking, with a hand near the power plug ... just in case.
---In ap-gto@..., wrote :
Do not tell the mount where it should unpark from. The mount always knows where it is, so unparking should always be from Last Parked, NOT from some park position that you think it is in. This is mentioned in all our literature and is repeated just about everywhere.
You can always park the mount anywhere that you wish, either at a random place or at a specific park position, or at a user defined park position. When unparking, DO NOT try to tell the mount where it is being unparked from. The mount knows exactly where it is, and if you try to tell it where it is and overwrite the internal memory, you run the risk of feeding it false information, and thus causing the mount to be pointing in the wrong direction. LET THE MOUNT UNPARK ITSELF!