New Parallax 360 Feedback Servo

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  • ercoerco Posts: 19,546
    Where's erco been lately? Head down and buried in work. This is my crazy time of year, New York Toy Fair (NYTF) is coming up mid-February, where I go to seek my fortune. I'm churning out lots of confidential toy prototypes to shop around to various manufacturers. The only freelance job I've taken recently is this prop for someone's toy gallery at NYTF. Their product is a variety of animal characters packaged in food containers. They described their vision for large prop, sort of a one-armed bandit game to promote their "which color will you get" theme. These 3 white containers will be fully decorated with rotating eyes. Video below is just my lame eye graphics for a progress update to the client. Anyway, each container is powered by... you guessed it, a Parallax 360 servo. They work well, I just need to manage the accelerations, the spinning drums are giant flywheels that could easily strip the servo gears otherwise. I'll try to get some video from NYTF of the finished prop.


    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • "I feel a blue, blue, blue coming up"... Hmmm, seems fixed :-]
    Livermore, CA (50 miles SE of San Francisco)
  • ercoerco Posts: 19,546
    Yes, I'm just testing the indexing at this phase. Will add real randomness next, using the old "how long was the button pressed" as a seed value. But the client did like my idea to always force a win on the first operation after powerup. When special guests or the media comes, you just secretly cycle the power and Lady Luck smiles.

    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • erco,

    You're having that much fun AND you get paid for it? You're livin' the dream, man! My hero!

    -Phil
    “Perfection is achieved not when there is nothing more to add, but when there is nothing left to take away. -Antoine de Saint-Exupery
  • ercoerco Posts: 19,546
    Must play to win! :)

    You're still MY hero PhiPi!
    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • @erco Put that on letsrobot.tv so I can try :)
  • ercoerco Posts: 19,546
    Good call! Maybe after Toy Fair, 'cuz I can't wear it out before then. :)
    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • ercoerco Posts: 19,546
    What's an Arduino library?


    :)
    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • @tomcrawford

    I have built a Activity bot and trying to get the "Juke-Bot" project posted by
    Andy Linsey - Spin tutorials.
    I have the 360 servos installed and I need to use your 360 driver to incorporated
    in the code for it to work.
    As I have it now the servos act very erratic due the wrong driver.

    I was studying your driver with the Demo and I do understand some spin and can write
    very basic stuff.
    In your servo driver and the demo code the following line of code appear and I do not
    understand what it is referring in relation to the code.

    The code line is : "dispThree(FBS.GetVelocity(TheServo))". As I undertand reference
    to a method has a period(.) after the method.
    I would very happy if you can explain the above line so it will help to understand
    the code structure.
    I would appreciate any assistance to get the "Juke-Bot" working with your 360 deriver.

    Thank you,

    Siri
  • @msiriwardena

    dispThree is a method within the demo program that just displays up to 3 decimal digits with leading blanks if needful.

    FBS.GetVelocity(TheServo) returns the current velocity of TheServo.



    Re-inventing the wheel is not a waste of time if, when you are done, you understand why it is round.
  • @tomcrawford
    I got confused with a call to an Object. This was call for an method.


    Thanks Tom and if by any chance have ideas to apply to the "Juke-Bot" I will be glad.


    Thanks again


    Siri
  • ercoerco Posts: 19,546
    edited 2019-02-17 - 01:12:29
    Update from New York Toy Fair: Here's the final installation of the props I built using the feedback 360 servos to feature the new "Foodie Roo" toy line. Working great on day one of a 4-day show. Hope the servo gears stand up to this heavy commercial use, I programmed very gentle accelerations and decelerations to minimize forces. These were decorated after I delivered them, I'm happy to see they look great and work great.

    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • Smooth! Love it.

  • So I think I have an application for 360 deg servo. I need just a normal R/C servo in every way, but with a swing of 360 deg instead of 180 deg.

    Can I use this servo just like a normal servo? Or to get the 360 capability, do I need to run it in continuous-motion mode and have my micro manually monitor the position feedback line?

    I was a little surprised this isn't spelled out in the product documentation. (unless I missed something)
    I am the Master, and technology my slave.
  • There are drivers available in spin, C, and (I think) blocky that allow you to just specify an angle.
    Re-inventing the wheel is not a waste of time if, when you are done, you understand why it is round.
  • The_Master wrote: »
    So I think I have an application for 360 deg servo. I need just a normal R/C servo in every way, but with a swing of 360 deg instead of 180 deg.

    Can I use this servo just like a normal servo? Or to get the 360 capability, do I need to run it in continuous-motion mode and have my micro manually monitor the position feedback line?

    I was a little surprised this isn't spelled out in the product documentation. (unless I missed something)

    Start with page one of this thread. There is a lot of code that members have written to test this device.
  • There are drivers available in spin, C, and (I think) blocky that allow you to just specify an angle.

    CPLD here.

    If anyone knows, to get the 360 capability, do I need to run it in continuous-motion mode and have my micro manually monitor the position feedback line?
    I am the Master, and technology my slave.
  • The_Master wrote: »
    There are drivers available in spin, C, and (I think) blocky that allow you to just specify an angle.

    CPLD here.

    If anyone knows, to get the 360 capability, do I need to run it in continuous-motion mode and have my micro manually monitor the position feedback line?

    Short answer is "yes". You drive the servo CW or CCW according to the offset of the control pulse from 1500 microseconds. You determine the current angle by measuring the duty cycle of the feedback pin. There is a description in the material in the downloads section of how the feedback works and a "C" example.
    Re-inventing the wheel is not a waste of time if, when you are done, you understand why it is round.
  • ercoerco Posts: 19,546
    WRT measuring the duty cycle of the feedback pin, you can either measure the pulse width or read the pin voltage with an ADC. I filtered the pin's PWM output with a 1uF cap and got excellent results.
    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • erco wrote: »
    WRT measuring the duty cycle of the feedback pin, you can either measure the pulse width or read the pin voltage with an ADC. I filtered the pin's PWM output with a 1uF cap and got excellent results.

    Interesting. What sort of precision were you able to obtain? +_1 degree?

    Re-inventing the wheel is not a waste of time if, when you are done, you understand why it is round.
  • " ...provides the functionality of a light-duty standard servo, continuous rotation servo, high-speed servo, and encoder in one convenient package... "

    They need to rewrite this description.
    I am the Master, and technology my slave.
  • ercoerco Posts: 19,546
    edited 2019-03-04 - 15:58:25
    erco wrote: »
    WRT measuring the duty cycle of the feedback pin, you can either measure the pulse width or read the pin voltage with an ADC. I filtered the pin's PWM output with a 1uF cap and got excellent results.

    Interesting. What sort of precision were you able to obtain? +_1 degree?

    No, not 1 degree, even most standard servos are +/- several degrees. I only used 8-bit resolution (255 steps) and my results felt typical of standard servos. What impressed me was the ADC reading's consistency and stability at the transition point, which jumped precisely from 5-178 IIRC, with no dead zone. So right there, you only have a resolution of 173 steps (not 360). Higher resolution is likely possible, but this reporter hasn't tried that yet. Also noteworthy is that I run everything (servos and electronics) off a single 5V supply (small switching wall wart). The specs recommend higher voltage but I'm a rebel.
    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • thejthej Posts: 217
    edited 2019-10-31 - 22:45:06
    @Ken Gracey
    Has there been any work done on making a slower/lower geared version of the Feedback 360 servo?

    J
  • thej wrote: »
    @Ken Gracey
    Has there been any work done on making a slower/lower geared version of the Feedback 360 servo?

    J

    Slower speed, no. If you have some ideas we need to consider share them.

    Geared version is a likely improvement to the current model which is being tested and put into production (same RPM).

    Ken Gracey
  • ercoerco Posts: 19,546
    SOMEBODY need to make an affordable servo gearbox to gear down standard-size servos. Servocity sells these aluminum monsters for $100+ (servo not included!). I could see $20 for a plastic version. https://www.servocity.com/tm-2645crh-cr-servo-gearbox

    Start by making the gears, do the pinion that presses onto a servo spline first. Are those available anywhere?

    438 x 280 - 26K
    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • erco wrote: »
    Start by making the gears, do the pinion that presses onto a servo spline first. Are those available anywhere?

    I have had good success using my laser to cut splines that will press fit onto a servo shaft. I have made both wheels and gears this way.
  • ercoerco Posts: 19,546
    W9GFO wrote: »
    I have had good success using my laser to cut splines that will press fit onto a servo shaft. I have made both wheels and gears this way.

    Impressive! What material are you cutting, maybe 1/8" plex?

    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • erco wrote: »
    W9GFO wrote: »
    I have had good success using my laser to cut splines that will press fit onto a servo shaft. I have made both wheels and gears this way.

    Impressive! What material are you cutting, maybe 1/8" plex?
    For servo splines either 1/8" cast acrylic or 1/8" delrin.

  • Same here with acetal (Delrin). I've done this numerous times with good success.

    -Phil
    “Perfection is achieved not when there is nothing more to add, but when there is nothing left to take away. -Antoine de Saint-Exupery
  • ercoerco Posts: 19,546
    Melted delrin releases formaldehyde fumes, a real gas to breathe and/or get in your eyes. JK, nasty stuff. But a fabulous material. Self-lubricating and taps very nicely.

    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
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