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Author Topic: Motors won't track  (Read 4901 times)

adfuller

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Motors won't track
« on: April 04, 2015, 15:07:44 »

I'm trying to set up my astroeq on an eq5 mount with the NEMA14 motors with a custom pulley set up.
I've got the scope to move when I use a high speed slew, but the sideral tracking won't move it at all.
The motors just 'hiss' or sound like a tapping noise. The pulleys are on firmly but easy to move manually and don't move even when I've had no load on them, they still don't budge. Any ideas what to do?
Cheers
Andy
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TCWORLD

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Re: Motors won't track
« Reply #1 on: April 04, 2015, 15:18:25 »

Hi Andy,

You may need to adjust the current limit for the motors, either up or down.

Which motors do you have? (What is their current rating).
Are they getting hot, or cool to the touch?

There is a tutorial for adjusting the current limit at: http://www.astroeq.co.uk/setcurrentlimit

Regards.
Tom.
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Tom Carpenter (AstroEQ)

adfuller

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Re: Motors won't track
« Reply #2 on: April 12, 2015, 07:53:50 »

Hi Thom,
The motors are the same ones you suggest on the FAQ http://www.omc-stepperonline.com/nema-14-bipolar-stepper-54v-08a-18ncm255ozin-14hs130804s-p-93.html
I've played with the current limit still have the issue. Changing the current alters the tone of the noise and they get warmer.  I can get the motors to move but not take a single step at a time.  played with the ascom controller and can get it to move when the rate is set to 2 or more, but not at one. I'm using the custom pulley config as I've sourced the parts as the FAQ suggests
Any suggestions?
Cheers
Andy
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TCWORLD

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Re: Motors won't track
« Reply #3 on: April 12, 2015, 14:13:56 »

Ah, one thing to check is if you have wired the motors correctly. This behaviour can be seen if you have crossed wires from each coil over. So if we say there is coil A and coil B, they should be wired to the RJ11 cable as: ABBA (or BAAB). If you have wired it as AABB (or BBAA), then it won't work properly - will sort of move when being stepped very quickly, but otherwise will just vibrate about.
 
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Tom Carpenter (AstroEQ)

adfuller

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Re: Motors won't track
« Reply #4 on: April 15, 2015, 12:38:05 »

I've spent a few hourson the problem and still a bit confused (admittedly that does take much  ???) and not got a solution yet.
I've tried to rewire the connections as suggested but think I did it correctly the first time as I saw the behaviour you mention when I tried to wired incorrectly.
The motors data sheet gives the connections as black-green for one coil and red-blue for the other.
The RJ11 give connections 2 to 5 so I've connected as 2-red, 3-black, 4-green , 5-blue. Does that seem right?
With this got the RA motor moving at the higher speeds seeming fine. The single step does seem to work, but the noise comming from the motors isn't great - a like durr with a brief pause every second. Changing the current make the noise louder but also heats up the motor much quicker so not really an option.
The DEC motor won't move at all on a single step, but will move at higher speeds.
I'm starting to wonder if it that the RJ11 connections as they are not the best.
I'm not sure what else to try as the connection was only the bit that I've done.  :-\
Any suggestions?
 
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TCWORLD

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Re: Motors won't track
« Reply #5 on: April 15, 2015, 14:10:26 »

The wiring sounds ok.

Are the motors currently connected to the mount? If so, do the run fine when not connected?
The only difference between driving at low speed and at high speed is that the microstepping mode changes to give more torque at high speed, but those motors are rated for about 3 times the torque of the ones I have, so they really shouldn't be struggling.

When there is nothing connected (RJ11's unplugged) and you spin the motor shaft, does it feel free running? (there will be a slight clicking feeling as the rotor steps).

The other thing to try is connecting the config utility and upload the firmware and configuration settings again, see if something had gone wrong.
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Tom Carpenter (AstroEQ)

adfuller

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Re: Motors won't track
« Reply #6 on: April 15, 2015, 14:38:58 »

I've pulled the motors from the mounts and they are now behaving. I can see (and feel) them stepping at small intervals.
The is a hissing coming from them but adjusting the current seems to reduce but not eliminate this. Is that normal
One thing is that I can 'force' them to rotate when powered on but not on the mount, but when on the mount and powered on, I can't move them.
Oh well, I''ll try and configure them on the bench and then add them to the mount when ready.
I'm testing them using the firmware update tool and as that gives me the ascom tester. What else can I adjust from the config that might?
Cheers for the assistance.
Andy
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TCWORLD

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Re: Motors won't track
« Reply #7 on: April 16, 2015, 02:54:50 »

Is something on the mount jamming/is it hard to turn the worm screws?

The hissing is quite normal, its the sound of the motor drivers using PWM to limit the current.
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Tom Carpenter (AstroEQ)

adfuller

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Re: Motors won't track
« Reply #8 on: April 23, 2015, 11:48:43 »

Hi Thom,
So I've taken some time to check the wiring and think I tracked the source to the connectors in the RJ11.
I've soldered them properly this time and the motors seem to working, however I think I've screwed up the current settings as they get hot very quickly.
So my question is how do I know where the minimum current setting is so I can work out what I should work upto?
There seems to be a 'flat' spot on the dial but where should that face?  I have a basic digital multi meter if that helps?
Cheers
Andy
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TCWORLD

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Re: Motors won't track
« Reply #9 on: April 23, 2015, 14:30:51 »

As you know the current for the motor (0.8A/phase), you can set this exactly as you have a multimeter. Basically there is a large Via in on the motor driver PCBs (big hole by one corner of the driver chip), if you measure the voltage between here and ground this will tell you what the current limit is, where:

    I = 2 * Vref

So you want to set the reference voltage to be between 0.4V and 0.45V is - a little bit over 0.4V should not be an issue.

Glad you found the issue in why the wouldn't turn properly.
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Tom Carpenter (AstroEQ)