1. Sitechservo
  2. Topics

Servo Motor Is Faulty

Ned Smith
 

I use this motor on a large DOB as the Azimuth drive.  The power supply is 20v.

Symptoms:  After power on any motion command courses the motor to run away.  Usually a run away stops after a few seconds and goes Blinky.This run away continues until power is shut off.  It even can be reversed by a hand pad key press.

I have checked lead continuity with a multi- meter.  I have replaced the optical encoder.  If you  swap motors, the bad motor is still bad.
If anyone has a spare motor of this type I would like to buy it from you.  Even if it doesn't work.
I want to stick with this motor type because I don't want to have to rebuild the drive hardware.
--
Ned Smith
Don W
 

Hi Ned,

There are several Pittman servos of your type, but not you voltage and gear ratio.
https://servocomponents.com/pages/pittman-9000-series-gear-motors
Don W
Dan Gray
 

Sounds like your encoder isn't working.
In ServoConfig, go to the Test and Tune button.  Turn both motors in manual.
The manual slider center position is zero PWM, going left the azimuth should turn CCW (birds eye view).
Using the manual slider, you can move the motors slow or fast (or anywhere in between), and it will ignore the encoders, but you can see the encoder position in the MOT [NNNN] ENC.
You can then see if the encoder is not working, going the wrong way, etc.
Dan


On Wed, Sep 21, 2022 at 11:34 AM Don W <westergren@...> wrote:
Hi Ned,

There are several Pittman servos of your type, but not you voltage and gear ratio.
https://servocomponents.com/pages/pittman-9000-series-gear-motors
Don W

Ned Smith
 

The optical encoder is new. I bought two so I have a spare.


On Fri, Sep 23, 2022 at 5:45 PM Dan Gray <grayarea@...> wrote:
Sounds like your encoder isn't working.
In ServoConfig, go to the Test and Tune button.  Turn both motors in manual.
The manual slider center position is zero PWM, going left the azimuth should turn CCW (birds eye view).
Using the manual slider, you can move the motors slow or fast (or anywhere in between), and it will ignore the encoders, but you can see the encoder position in the MOT [NNNN] ENC.
You can then see if the encoder is not working, going the wrong way, etc.
Dan


On Wed, Sep 21, 2022 at 11:34 AM Don W <westergren@...> wrote:
Hi Ned,

There are several Pittman servos of your type, but not you voltage and gear ratio.
https://servocomponents.com/pages/pittman-9000-series-gear-motors
Don W



--
Ned Smith
Dan Gray
 

did you try the test and tune like I suggested?
Dan


On Sat, Sep 24, 2022 at 4:59 AM Ned Smith <smithned753@...> wrote:
The optical encoder is new. I bought two so I have a spare.

On Fri, Sep 23, 2022 at 5:45 PM Dan Gray <grayarea@...> wrote:
Sounds like your encoder isn't working.
In ServoConfig, go to the Test and Tune button.  Turn both motors in manual.
The manual slider center position is zero PWM, going left the azimuth should turn CCW (birds eye view).
Using the manual slider, you can move the motors slow or fast (or anywhere in between), and it will ignore the encoders, but you can see the encoder position in the MOT [NNNN] ENC.
You can then see if the encoder is not working, going the wrong way, etc.
Dan


On Wed, Sep 21, 2022 at 11:34 AM Don W <westergren@...> wrote:
Hi Ned,

There are several Pittman servos of your type, but not you voltage and gear ratio.
https://servocomponents.com/pages/pittman-9000-series-gear-motors
Don W



--
Ned Smith
Ned Smith
 

Not yet. But soon. 

Ned Smith


On Sep 26, 2022, at 4:29 PM, Dan Gray <grayarea@...> wrote:


did you try the test and tune like I suggested?
Dan

On Sat, Sep 24, 2022 at 4:59 AM Ned Smith <smithned753@...> wrote:
The optical encoder is new. I bought two so I have a spare.

On Fri, Sep 23, 2022 at 5:45 PM Dan Gray <grayarea@...> wrote:
Sounds like your encoder isn't working.
In ServoConfig, go to the Test and Tune button.  Turn both motors in manual.
The manual slider center position is zero PWM, going left the azimuth should turn CCW (birds eye view).
Using the manual slider, you can move the motors slow or fast (or anywhere in between), and it will ignore the encoders, but you can see the encoder position in the MOT [NNNN] ENC.
You can then see if the encoder is not working, going the wrong way, etc.
Dan


On Wed, Sep 21, 2022 at 11:34 AM Don W <westergren@...> wrote:
Hi Ned,

There are several Pittman servos of your type, but not you voltage and gear ratio.
https://servocomponents.com/pages/pittman-9000-series-gear-motors
Don W



--
Ned Smith
Ned Smith
 

Went to the observatory today to perform your test.  Room had many new wasp nests.  Sprayed killer and left quickly.  
I will try again tomorrow.

On Mon, Sep 26, 2022 at 4:29 PM Dan Gray <grayarea@...> wrote:
did you try the test and tune like I suggested?
Dan

On Sat, Sep 24, 2022 at 4:59 AM Ned Smith <smithned753@...> wrote:
The optical encoder is new. I bought two so I have a spare.

On Fri, Sep 23, 2022 at 5:45 PM Dan Gray <grayarea@...> wrote:
Sounds like your encoder isn't working.
In ServoConfig, go to the Test and Tune button.  Turn both motors in manual.
The manual slider center position is zero PWM, going left the azimuth should turn CCW (birds eye view).
Using the manual slider, you can move the motors slow or fast (or anywhere in between), and it will ignore the encoders, but you can see the encoder position in the MOT [NNNN] ENC.
You can then see if the encoder is not working, going the wrong way, etc.
Dan


On Wed, Sep 21, 2022 at 11:34 AM Don W <westergren@...> wrote:
Hi Ned,

There are several Pittman servos of your type, but not you voltage and gear ratio.
https://servocomponents.com/pages/pittman-9000-series-gear-motors
Don W



--
Ned Smith



--
Ned Smith
Don W
 

Hi Ned,

Well, that is no fun at all.  I hope the spray is complettely successful.

Don W
Ned Smith
 

I performed the tests today.  Both motors ran OK in manual mode.  PWM moved as expected for the Alt motor.
PWM for the suspect AZ motor did not change.  I believe this points to the encoder on the AZ motor.
However this is a brand new device.
I feel the problem is in the connector between the motor and the controller.  I have tested continuity on all wires with the connector on the bench.  I believe something happens when the connector is plugged into the encoder.  But I don't know how to prove that.

On Mon, Sep 26, 2022 at 4:29 PM Dan Gray <grayarea@...> wrote:
did you try the test and tune like I suggested?
Dan

On Sat, Sep 24, 2022 at 4:59 AM Ned Smith <smithned753@...> wrote:
The optical encoder is new. I bought two so I have a spare.

On Fri, Sep 23, 2022 at 5:45 PM Dan Gray <grayarea@...> wrote:
Sounds like your encoder isn't working.
In ServoConfig, go to the Test and Tune button.  Turn both motors in manual.
The manual slider center position is zero PWM, going left the azimuth should turn CCW (birds eye view).
Using the manual slider, you can move the motors slow or fast (or anywhere in between), and it will ignore the encoders, but you can see the encoder position in the MOT [NNNN] ENC.
You can then see if the encoder is not working, going the wrong way, etc.
Dan


On Wed, Sep 21, 2022 at 11:34 AM Don W <westergren@...> wrote:
Hi Ned,

There are several Pittman servos of your type, but not you voltage and gear ratio.
https://servocomponents.com/pages/pittman-9000-series-gear-motors
Don W



--
Ned Smith



--
Ned Smith
Don W
 

Hi Ned,

Monitor the encoder output voltages with servo stopped and also running slow.  The voltage when stopped should eother be near zero or near 5 volts.  When running the volge should be around 2.5 volts.  Compare both your servos.  If your "bad" servo doesn't compare then trace the wiring.

Don W
Ned Smith
 

Should I still be in TEST AND TUNE for this observation?


On Wed, Oct 5, 2022 at 6:00 PM Don W <westergren@...> wrote:
Hi Ned,

Monitor the encoder output voltages with servo stopped and also running slow.  The voltage when stopped should eother be near zero or near 5 volts.  When running the volge should be around 2.5 volts.  Compare both your servos.  If your "bad" servo doesn't compare then trace the wiring.

Don W



--
Ned Smith
Don W
 

Hi Ned,

Test and Tune is fine to measure voltages, but not SiTechexe because you can't stop easily - SiTechexe holds servos stopped by reversing voltages.

Don W
Ned Smith
 

I don't see voltages in TEST and TUNE.   Where should I be looking?


On Thu, Oct 6, 2022 at 12:11 PM Don W <westergren@...> wrote:
Hi Ned,

Test and Tune is fine to measure voltages, but not SiTechexe because you can't stop easily - SiTechexe holds servos stopped by reversing voltages.

Don W



--
Ned Smith
Don W
 

Hi Ned,

Use Test and Tune to move the servo and to stop it.  You measure the voltages of the encoder with your volt meter.

Don W
Ned Smith
 

Thanks Don.
I am not an electronics guy so I need pretty explicit instructions to carry out tasks, 
I understand the following:
In TEST and TUNE, stay in manual mode and move the motor with the manual sliders.
At the controller,  place one multimeter lead on ???? and the other on ???? to check for a voltage between +5 and -5.

On Thu, Oct 6, 2022 at 7:27 PM Don W <westergren@...> wrote:
Hi Ned,

Use Test and Tune to move the servo and to stop it.  You measure the voltages of the encoder with your volt meter.

Don W



--
Ned Smith
Don W
 

Hi Ned,

On the Servo II controller, you measure the voltage between Ground and the ME A, then the ME B for each servo.  With the servo not moving, these voltages should be either near zero or near 5 volts.  With the servo moving (Test and Tune) the reading should be around 2.5 volts.  If you don't see these voltages, then the cable or the encoder is bad.  In case it reads bad, make sure the +5 volts on the controller is really 5 volts.

Don W
Ned Smith
 

After all this time I think I have inadvertently found the problem.  The encoder disc has become detached from the rotor.
Can that be fixed? 

On Fri, Oct 7, 2022 at 11:17 AM Don W <westergren@...> wrote:
Hi Ned,

On the Servo II controller, you measure the voltage between Ground and the ME A, then the ME B for each servo.  With the servo not moving, these voltages should be either near zero or near 5 volts.  With the servo moving (Test and Tune) the reading should be around 2.5 volts.  If you don't see these voltages, then the cable or the encoder is bad.  In case it reads bad, make sure the +5 volts on the controller is really 5 volts.

Don W



--
Ned Smith
Che
 

the disk is held in place by a very small setscew.   You need an allan wrench that fits.  but they can be removed and replace on those pitman gearmotors


On 10/28/2022 2:11 PM, Ned Smith wrote:

After all this time I think I have inadvertently found the problem.  The encoder disc has become detached from the rotor.
Can that be fixed? 

On Fri, Oct 7, 2022 at 11:17 AM Don W <westergren@...> wrote:
Hi Ned,

On the Servo II controller, you measure the voltage between Ground and the ME A, then the ME B for each servo.  With the servo not moving, these voltages should be either near zero or near 5 volts.  With the servo moving (Test and Tune) the reading should be around 2.5 volts.  If you don't see these voltages, then the cable or the encoder is bad.  In case it reads bad, make sure the +5 volts on the controller is really 5 volts.

Don W


--
Ned Smith
Ned Smith
 

Any idea what size wrench is?

Ned Smith


On Oct 28, 2022, at 5:23 PM, Che <cheman@...> wrote:



the disk is held in place by a very small setscew.   You need an allan wrench that fits.  but they can be removed and replace on those pitman gearmotors


On 10/28/2022 2:11 PM, Ned Smith wrote:
After all this time I think I have inadvertently found the problem.  The encoder disc has become detached from the rotor.
Can that be fixed? 

On Fri, Oct 7, 2022 at 11:17 AM Don W <westergren@...> wrote:
Hi Ned,

On the Servo II controller, you measure the voltage between Ground and the ME A, then the ME B for each servo.  With the servo not moving, these voltages should be either near zero or near 5 volts.  With the servo moving (Test and Tune) the reading should be around 2.5 volts.  If you don't see these voltages, then the cable or the encoder is bad.  In case it reads bad, make sure the +5 volts on the controller is really 5 volts.

Don W


--
Ned Smith
Russell R
 

Ned,

If you have hubdisk-1, then I believe the wrench size is .035" with a torque of 2-3 inch pounds and a .020" gap from sensor side of module.  A piece of thin .020" cardboard makes a good temporary spacer since it's kinda hard to get inside the  encoder housing........and it won't scratch the encoder disk.   

Hope this helps,
Russell R.

1 - 20 of 24