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Author Topic: Servo and Motor Driver incompatibility  (Read 635 times)
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Dear Forum,
I have been using an Arduino Uno and a Critical Velocity 15 Amp Bidirectional PWM Motor Speed Controller to control a 12V 10 AMP motor. Things have been running perfectly until I added a SparkFun Large Servo to the Arduino.  Now the motor will not run in reverse.   SparkFun suggests a separate power supply for the servo or noise filtering. 
I have a robust 12V power supply for the Motor Controller.  Rather not add another 5V supply for the servo. 
Any suggestions on how to add the servo without throwing a wrench in to the soup?   Greatly appreciated.
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This sounds like a code problem. Did you include the Servo library in your code? On a non-Mega Arduino that will disable PWM on pins 9 and 10.
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Quote
Rather not add another 5V supply for the servo.

Well, direct 12v to the servo may kill it, and the arduino is usually inadequate to power a servo itself. You might power the servo via a 7805 regulator chip connected to the 12v power supply.
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You might power the servo via a 7805 regulator chip connected to the 12v power supply.

As they might say on 9gag... "You make a suggestion like that on this forum and you gonna have a bad time"  smiley-cool
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You might power the servo via a 7805 regulator chip connected to the 12v power supply.

As they might say on 9gag... "You make a suggestion like that on this forum and you gonna have a bad time"  smiley-cool

Not sure why. I've had a pair of web cam pan/tilt servos powered like below 24/7 since 2004 without any issues.

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This sounds like a code problem. Did you include the Servo library in your code? On a non-Mega Arduino that will disable PWM on pins 9 and 10.
I believe I have cleared the code.  Sketch runs fine with servo control lead disconnected.  I did include the library in the code.
I also ran a sketch with only the servo code and that runs fine.
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You might power the servo via a 7805 regulator chip connected to the 12v power supply.

As they might say on 9gag... "You make a suggestion like that on this forum and you gonna have a bad time"  smiley-cool

Could you elaborate on that please?
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Some members are "against" regulators like that because they waste power.

In a 7805 style regulator, the input current is always the same as the output current, so since it's at a higher voltage, the difference in input - output voltage, times the current, is the wasted power in watts.

That waste manifests as heat.....
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Some members are "against" regulators like that because they waste power.

In a 7805 style regulator, the input current is always the same as the output current, so since it's at a higher voltage, the difference in input - output voltage, times the current, is the wasted power in watts.

That waste manifests as heat.....
Thank you JimboZA.  Would you agree that it is a power problem and not a noise problem ?  Do you have a alternate recommendation from the 7805 regulator?
Thanks again for your assistance.
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