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Author Topic: DIY Yellow Servo  (Read 1839 times)

BaldwinK

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DIY Yellow Servo
« on: November 29, 2016, 01:29:59 PM »
Continuing to investigate alternative servo options I ventured into imaginary lands with the quaternion mimic.  Back to earth for real now with a simple resistive feedback servo based on the cheap and popular yellow motor.  Having now struggled with most of the clever stuff this one was so easy I have to share it.


One problem for a bot with many motors is the power supply.  Most servos have motor and control sharing the same stabilised supply.  Separate the two and life is much easier plus the motor can be pushed harder.  At 12 volts the yellow motor gets quite lively, it also runs hot - as does the driver so we have to watch duty cycle.  This demo uses a 2S lipo at around 8 volts but you could use 5 volts of course.

The ceramic metal potentiometer should last but I have already thrashed my prototype to fail so the design should allow for replacing this delicate part.  I have made up a construction document to show the salient issues but it is not a bible.  Most of you will be able to improve on something here depending on your access to resources and tools.  A 3D printer might be handy!  I still potter with thin plywood and white glue because it is cheap and forgiving.

I use a Nano and two quad half-bridges for my test rigs so the diagram and code may appear to use strange pins.  Look up Brett Beauregard’s work for understanding PIDs.  The Excel graphs show the servo response to the demo stepping – you can see the overshoot.  Tuning is an art that still frustrates.  Some calibration will be required once your cermet is mounted.

*Construction.doc
*Y_Servo.ino
*Diagrams.doc







AmandaG

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Re: DIY Yellow Servo
« Reply #1 on: August 06, 2019, 01:08:09 PM »
Continuing to investigate alternative servo options I ventured into imaginary lands with the quaternion mimic.  Back to earth for real now with a simple resistive feedback servo based on the cheap and popular yellow motor.  Having now struggled with most of the clever stuff this one was so easy I have to share it.


One problem for a bot with many motors is the power supply.  Most servos have motor and control sharing the same stabilised supply.  Separate the two and life is much easier plus the motor can be gimp freejobalert notepad++ pushed harder.  At 12 volts the yellow motor gets quite lively, it also runs hot - as does the driver so we have to watch duty cycle.  This demo uses a 2S lipo at around 8 volts but you could use 5 volts of course.

The ceramic metal potentiometer should last but I have already thrashed my prototype to fail so the design should allow for replacing this delicate part.  I have made up a construction document to show the salient issues but it is not a bible.  Most of you will be able to improve on something here depending on your access to resources and tools.  A 3D printer might be handy!  I still potter with thin plywood and white glue because it is cheap and forgiving.

I use a Nano and two quad half-bridges for my test rigs so the diagram and code may appear to use strange pins.  Look up Brett Beauregard’s work for understanding PIDs.  The Excel graphs show the servo response to the demo stepping – you can see the overshoot.  Tuning is an art that still frustrates.  Some calibration will be required once your cermet is mounted.

*Construction.doc
*Y_Servo.ino
*Diagrams.doc
Wow thanks for this post. Helped me a lot.

Thanks and Regards,
Amanda
« Last Edit: August 15, 2019, 02:28:57 PM by AmandaG »

 

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