Servo Motor problem

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maranha
 
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Servo Motor problem

Post by maranha »

I recently bought a "standard" servo motor TowerPro SG-5010.
And set it up according to the instructions in: https://learn.adafruit.com/controlling- ... bone-black
Cannot get the motor to turn.
Tried both as root and as a normal user.
Has anyone got this project to work according to the instructions on the web link?
Could I have a defective servo motor? If so can I get a refund?

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adafruit_support_rick
 
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Re: Servo Motor problem

Post by adafruit_support_rick »

Please post some clear, detailed pictures of your connections.

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maranha
 
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Re: Servo Motor problem

Post by maranha »

Don't have the thing in front of me or a good way to post a picture but verified the wiring several times.
Is there a quick/simple test to verify that the motor works at all?
I think I probably have a DOA motor in which case I'd like to get a refund.

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weldeng
 
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Re: Servo Motor problem

Post by weldeng »

I am having the same problem. I have tried two different servos Tower Pro SG-5010 ad smaller SG-90. Neither rotates. I set up following the Adafruit tutorial instructions. I have Rev C board with Debian.

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adafruit_support_bill
 
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Re: Servo Motor problem

Post by adafruit_support_bill »

Please post photos showing your connections.

Do your servos make any noise or twitch at all when first connecting power?
Do they hum or vibrate at all when powered?
When not powered, are you able to turn the shafts by hand with moderate resistance?

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maranha
 
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Re: Servo Motor problem

Post by maranha »

Answers to all above questions is: no.
The motor appears to be dead.

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adafruit_support_bill
 
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Re: Servo Motor problem

Post by adafruit_support_bill »

@marhana - please contact [email protected] with a link to this thread for a replacement TowerPro SG-5010.

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tdicola
 
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Re: Servo Motor problem

Post by tdicola »

For folks that are still running into this issue with good servos, I found you might need to invert the polarity of the PWM signal to make it work. I updated the guide page to call out that you can pass an optional 4th parameter to PWM.start with a value of 1 to invert the signal. Take a look at the updated page here and give it a shot to see if it works: https://learn.adafruit.com/controlling- ... on-console

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weldeng
 
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Re: Servo Motor problem

Post by weldeng »

weldeng wrote:I am having the same problem. I have tried two different servos Tower Pro SG-5010 ad smaller SG-90. Neither rotates. I set up following the Adafruit tutorial instructions. I have Rev C board with Debian.

I fixed the problem. On starting the program the motor would rotate fully counterclockwise and would not budge thereafter. Changing two lines of your code fixed the problem. Corrected code is provided below.


PWM.start(servo_pin, (100-duty_min), 60) changed to PWM.start(servo_pin, duty_min, 60)

and

duty = 100 - ((angle_f / 180) * duty_span + duty_min) was changed to duty = ((angle_f / 180) * duty_span + duty_min)


Thanks

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weldeng
 
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Re: Servo Motor problem

Post by weldeng »

tdicola wrote:For folks that are still running into this issue with good servos, I found you might need to invert the polarity of the PWM signal to make it work. I updated the guide page to call out that you can pass an optional 4th parameter to PWM.start with a value of 1 to invert the signal. Take a look at the updated page here and give it a shot to see if it works: https://learn.adafruit.com/controlling- ... on-console

I am curious as to why some servos need the polarity inverted and some dont? Would it vary between two servos of the same model, for example the Tower Pro SG-5010 I used vs the SG-5010 used in the Adafruit tutorial?
Thanks

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adafruit_support_bill
 
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Re: Servo Motor problem

Post by adafruit_support_bill »

It is not a servo problem. It appears to be due to some library change in recent BBB releases.

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tdicola
 
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Re: Servo Motor problem

Post by tdicola »

Yep servos always want the same signal, but my suspicion is that perhaps the older Angstrom OS had different behavior with PWM compared to Debian.

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maranha
 
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Re: Servo Motor problem

Post by maranha »

@tdicola, @adafruit_support_bill - thanks!
I was about to send photo and/or return servo but Inverting polarity worked.
@weldeng - have not tried your approach yet.
I have to be 'root' to get program to work.
Looks like libraries need updating!

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nick_karam
 
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Re: Servo Motor problem

Post by nick_karam »

I have the same problem though inverting polarity did not fix it. MICRO-SERVO SG90
-Do your servos make any noise or twitch at all when first connecting power? No.
-Do they hum or vibrate at all when powered? No.
-When not powered, are you able to turn the shafts by hand with moderate resistance? Yes.
The commands by the console are sent with no error feedback and the program too.
It just won't reply. Any suggestions? Thank you in advance.

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adafruit_support_bill
 
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Re: Servo Motor problem

Post by adafruit_support_bill »

-Do your servos make any noise or twitch at all when first connecting power? No.
-Do they hum or vibrate at all when powered? No.
What are you using for a power supply for the servo? Post a photo of how you have it hooked up.

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