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Mecanum Wheeled Robot with Machine Vision - Page 7 — Parallax Forums

Mecanum Wheeled Robot with Machine Vision



  • Duane DegnDuane Degn Posts: 10,588
    edited 2014-08-13 20:50
    davidgitz wrote: »
    Looks like a great robot! At FAST Robotics we are offering a nice solution for using your Quickstart on a Robotics project, the Robot Shield.
    Attachment not found.
    Some basic info:
    -4 Servo Outputs externally powered
    -9 GPIO Pins
    -8 Analog Inputs
    -SD Card
    -Serial Port

    We are currently working on the new version of this board to make minor improvements and move the headers to the exterior of the board for connecting shields together. Here is our github page for the Robot Shield
    and a link to a demo video on a robot:
    We have a lot of other things we're working on too. Check out our facebook for more info:

    I'm not sure why you chose this thread to announce your Robot Shield since the Mecanum wheeled robot needs at least 16 I/O pins to read the encoders and control the motors and I can only see a total of 13 available I/O pins on your shield.

    IMO, you'd be better off showing your design in the Propeller forum and (if you're interested in others' opinions) ask for feedback on the design. If you're not looking for feedback then a post showing your robot to the robot forum may be a good idea.
  • ercoerco Posts: 20,248
    edited 2014-08-13 22:25
    Cool board, David! The more Prop boards the better and matching the Quickstart form factor and pinout sure makes things simple. I'm not certain, but you might be the first to call your accessory board a "shield" for the Propeller, that's mostly an Arduino thing. :)

    I didn't see a video on your page, but I'll look forward to seeing & hearing more about it. Per Duane, please post in Robotics for more eyes-on.

    How much is your board?
  • Duane DegnDuane Degn Posts: 10,588
    edited 2014-08-14 12:14
    erco wrote: »
    I didn't see a video on your page,

    There's a link to a video in post #181.
    David uses the Robot Shield to turn a remote controlled car into a . . . remote controlled car. Okay David, you need to make a better demo video showing your robot being a robot and not a remote controlled toy.

    Though technically my robot is also a remote controlled car/toy, I have had it perform multiple autonomous figure 8's.

    @David, you should get your robot to drive in a figure 8 and post the video to this thread.
  • davidgitzdavidgitz Posts: 7
    edited 2014-08-15 04:17
    Hi guys, thanks for the feedback.
    @Duane - We are doing a revision on this board to give more I/O options so hopefully this won't be an issue. We will definitely have to post more videos!

    @erco - Right now we are thinking around $50-$55 including assembly and shipping.

    Thanks again! I also updated our Datasheet to add the Bill of Materials. Sorry for hijacking your thread.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2014-08-15 07:09
    davidgitz wrote: »
    Sorry for hijacking your thread.

    Not a problem. This thread has been to Cuba and back so many times, I sometimes forget it's original destination.

    IMO, you're much more likely to have success with your board if you get some feedback about it before going into production. I've personally learned a lot by posting a board design and then letting others tell me where improvements could be made.

    I think you're making a mistake using level shifters. There are very few 5V sensors which won't work with 3.3V logic and the level shifters interfere with some bi-directional communications (have you tested your level shifters with a Ping?). There are also a lot of 3.3V sensors now which may need another set of level shifters if used with 5V logic.

    I also think it's a waste to use I/O pins on LEDs. At least let the LED pins do double duty like the QuickStart's LEDs. I also think you should bring the I2C lines out. There are a lot of I2C devices and these two pins are already being used for I2C so why not make use of them?

    I like having an 8 channel ADC chip which looks like it hasa nice ground pour between the input lines. I think you might want to move the ADC chip closer to the pins. Since the ADC is a SPI device and the uSD card is SPI, you could share some of the pins and just make sure the ADC has its own CS pin. Adding the ADC could just cost one I/O pin (which are in short supply on a robot).
  • davidgitzdavidgitz Posts: 7
    edited 2014-08-18 18:48
    @Duane - Thanks again for the feedback man! We really appreciate it. I posted your suggestions to our github repo for the Robot Shield We love feedback, which is why we're posting to the community before we jump into manufacturing.

    We haven't gotten around to a figure-8 yet but I took your suggestion and made another demonstration video that shows off 2 ultrasonic sensors (A Ping in the Front on a Pan Servo and a Maxbotix in the Rear) that provide a basic level of obstacle detection.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2015-01-27 12:21
    I'm a "Featured Project" on Hackaday.


    Pretty cool!
  • NWCCTVNWCCTV Posts: 3,629
    edited 2015-01-27 18:32
    Way to go Duane!!!
  • ercoerco Posts: 20,248
    edited 2015-01-27 23:33
    Most excellent! Congrats Boss!
  • PublisonPublison Posts: 12,366
    edited 2015-01-28 08:04

    Couldn't have happened to a nicer guy!
  • kuekue Posts: 16
    edited 2015-02-03 20:41
    I want to buy it, how much :)
  • Duane DegnDuane Degn Posts: 10,588
    edited 2015-02-21 14:07
    Dagu, the company which makes the Rover 5 has changed the type of encoders used inside the gearbox. The resolution of the encoders hasn't changed but the encoders use magnets and Hall-effect sensors rather than optical encoders.

    Apparently the new encoders can be powered with 3.3V so they can be connected to the Propeller without using a series resistor. I haven't tried it myself yet, but I think the optical encoders will also work when powered 3.3V instead of 5V.

    As has been mentioned a couple of times in this thread, the Rover 5 platform is a bit underpowered for these large Mecanum wheels. With encoder feedback, the underpowered motors don't really create an issue but I'm interested in trying the Vex Mecanum wheels with a different set of motors and encoders.

    I have a set of four of Parallax's motor with encoders and I plan to make a Mecanum wheeled robot using these motors in the near future.

    Once I build the new robot, I'll work on updating the code used to control the robot.
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