Baaaaaaad night last night...(electronics help?)

[GazOC]

Last night I used a different extension lead and power lead, after working OK for a while the RA motor stopped working. I took the motors out and the dec is fine but when I switch on the mount and align, the RA motor will only make 1/2 a turn and then stop and will not take anymore input from the hand controller. The motor will move freely by hand but will not do more than the half turn when aligning and will not move (or try to move) after that.

I'm totally out of my depth with anything to do with electronics/ motors, I suspect the prognosis isn't good (ie fried motor). My only glimmer of hope is that the RA will make that initial half turn every time I ask it to align the GOTO.

Any ideas?

[geppetto]

Are both motors the same Gaz

If so could you swap them round and then if the motor

still refuses its somat wrong with the drive electronics.

If it does turn and the other doesn't then its the motor.

Hope its something simple mate :?

[GazOC]

They are on different sized connectors, the dec motor works fine but I can't plug the RA motor into the dec motors socket.

[daz]

Which mount Gaz?

[GazOC]

Which mount Gaz?

Guess!!! My most expensive one, EQ6 Skyscan.

[geppetto]

Have you confirmed that the RA axis of the scope isnt binding at some point and stalling

the motor or is everything mechanically free to move?

[GazOC]

Yep, I've got the motors out of the mount and connected them to the power. The dec runs fine but the RA just makes a half turn and then stops even trying. The RA is mechanically free, I did hear a "funny" click from the mount just before the RA failed for the first time though.

[geppetto]

Seems an odd thing for even a faulty motor to do, turn half a turn and stop :?

Are they stepper motors?

[Ambermile]

Yup - and in that case it may just be a loose wire. Or a dead winding...

[GazOC]

Seems an odd thing for even a faulty motor to do, turn half a turn and stop :?

Are they stepper motors?

Yes, stepper motors.

The only bit of hope I've got left is that the motor is free and it wil turn under power.l

[Ambermile]

Ah. Thing is, it's a stepper motor. If it's "free" then it's not as it should be...

[geppetto]

Strange...

Right How are you driving the motor?

Are you pressing an RA forward backward button (manual control)

or is the goto gizmo turning the motor?

When the motor stops after half a turn does it then go for another half turn when you press go again?

Sorry to be vague but I'm trying to visualise what your seeing

[GazOC]

Ah. Thing is, it's a stepper motor. If it's "free" then it's not as it should be...

I'm guessing that noise I heard is the teeth of an internal cog ripping off? The half turn is where there are teeth left?

Funny thing is, after that half turn I can't hear anything moving (or trying to move) in the motor....surely something should at least be trying to rotate?

[Ambermile]

Wel, the stepper will not have gears, just two or four windings. I can't remember if there's a gearbox on the Skyscan motors though - but I would have thought so. Unlucky to break one...

[geppetto]

Arthur

Have you any idea how the skyscan knows what position its in.

Would there be some encoders on the RA/DEC shafts.

Just wondering if something is telling the motor that its got where it needs to be

and turns it off.

Could do with a link to some techy info about that setup

[GazOC]

I'm pretty sure the encoders are in the motors, theres no wires going into the mount from the motors.

[geppetto]

It doesnt have to be using encoders, it could be the electronics knows where the mount is

by how many steps its taken.

Thing I would try is drive the motor till it stops after half a turn then with the power still on

try to physically turn the motor by hand. If you can then theres no power on it (or a duff winding)

Also you need to find out by marking it or whatever, if it stops in exactly the same place after the half turn.

If it stops in more than one place then Im not convinced its a duff motor

[GazOC]

Gep,

When it stops after the half turn it still moves freely by hand, if I switch off and then turn it back on the motor will do another half turn from the point at which it stopped last time.

The half turn starts and stops at different places each time I power it up (I checked this last night).

Gaz

[Ambermile]

No - no encoders G - with steppers they are not needed.

Arthur

[geppetto]

Plot thickens...

If it was a duff motor and failed to drive past a certain position for whatever reason

then you would sort of expect it to fail at the same point.

Your saying that it stops at any position after half a turn so at some point it must have

driven through the positions where it stopped before.

Its as though the electronics are telling the motor to turn 180' and then the power turns off

leaving the motor able to be turned by hand.

Curious...will put me thinking cap on.

By the way are you still using the different cables that you started using last night?

If so, try with the old known good cables youve used up till then

[GazOC]

Gep,

It's not exactly 180 more like 120 ("half"a rough guess), but it does seem to be the same amount every time.

[geppetto]

Thing is Gaz, if its say a 1.8 degree per step motor and say its gone round 180 degrees

then its done 100 steps and has used all its coils many times to get that far round and it

would be using the same coils for the second half turn,

so I still favour the power being lost to it rather than a duff motor but then I am getting a bit long in

the tooth for this sort of thing.

[Ambermile]

OK - if you have an ohmeter try this

http://tinyurl.com/nrjhp

but I'm with G on this, either the shaft comes loose because it's a cheap stepper motor or it's a drive issue.

Arthur

[geppetto]

Gaz, if your not already, sign up to the Yahoo EQ6 group and see if there are any

tips on there.

Also, I came across a long review of the EQ6 Skyscan mount and the bloke commented

that the stepper motors electronics and encoders were nicely protected within the

case on the DEC shaft.

He seems to think there's some encoders (he might be wrong though )

If there are encoders, one might have broke off :?

[GazOC]

Right, I swapped the motor connections around (I was wrong before!!), both motors work faultlessly when plugged into either socket on the board when only one motor is plugged in.

The problem arises when I plug both motors in and it happens to both motors, I'm guessing the mount isn't getting enough power? I'm using the same leads as I've always used so it must be the electronics on the control board?

Gep, I posted in the EQ6 Yahoo group last night, I'm getting some ideas back. Cheers.