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Thread: Numa V2 - Quad Mech

  1. #11
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    Re: Numa V2 - Quad Mech

    Fourbar linkage almost identical to original Numa's. That said, I got lazy and didn't model the 3mm rods, and made a set of linkages that would require me drilling a hole in the AEG, whoops. Recutting that linkage tonight (easy design tweak), and then doing wiring.

    Chassis before wiring: (as always, click to embiggen)
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  2. #12
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    Re: Numa V2 - Quad Mech

    Well I killed my HydraBus last night. Turns out they are not easy to get extras of (not inclined to pay 120 euros for board + express shipping that would get here Thursday night). So I'll just have to wait until next year (and December?). Definite bummer. I'll be at robogames on Saturday though!

    This was my mistake (backside of the 6 connector dynamixel interface board):
    Click image for larger version. 

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  3. #13

    Re: Numa V2 - Quad Mech

    The TTL bus doesn't like 12V. I hope you didn't have any servos plugged in. That can get (ahem) very expensive!

    Don't you have an OpenCM or something to use instead? It'd be a shame to bring no bot :-(

  4. #14
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    Re: Numa V2 - Quad Mech

    Which is why I made my own inline 6-port hub with buss cap, reinforced power traces, and separate vias for power input wires. Whenever I need a new batch of them, they will be using an inline 7-port layout (one upstream with comm only) and an adorable XT-30 instead of bare vias.
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    bleh

  5. #15

    Re: Numa V2 - Quad Mech

    Yeah, the power traces are quite thin in some places on that Robotis hub!
    There is a version of it (from Robotis) with an electrolytic cap and a 5.5 millimeter barrel connector, too.
    Then again, barrel connectors are not particularly firm.
    I make my own, like Tician, although I have a preference for screw connectors.
    Actually, I hate screw terminals, but I have everything else even more!

    Anyway, this is about Gertlex, and the manly guts he shows to post a warning image for everyone to learn from out of his failure!
    Thanks, man, you're making the world a better place!

  6. #16

    Re: Numa V2 - Quad Mech

    Quote Originally Posted by Gertlex View Post
    Well I killed my HydraBus last night. Turns out they are not easy to get extras of (not inclined to pay 120 euros for board + express shipping that would get here Thursday night). So I'll just have to wait until next year (and December?). Definite bummer. I'll be at robogames on Saturday though!

    This was my mistake (backside of the 6 connector dynamixel interface board):
    Click image for larger version. 

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    If you have a solder station you might be able to replace the microcontroller. We've been working on one of our club mechs and destroyed a OpenCM board in the same way. Someone in the club replaced the micro on the OpenCM board and reloaded the boot loader.

  7. #17
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    Re: Numa V2 - Quad Mech

    I definitely plan to try the replacement of the microcontroller at some point with the hot air reflow at work, but that's not happening this week.

    My code is micropython, and there really aren't too many boards that support micropython out there. While I did port from C to Python, I'm not too interested in killing myself getting it working on another board that will fit in my mech and has sufficient UARTs.

    And yeah, may have fried 4-5 servos, but haven't tested those yet. (Well, I tested one, and the red led turns on and off as expected)

    I should enhance the power rails on that board for future use, too, aye.

  8. #18

    Re: Numa V2 - Quad Mech

    [qutoe]Someone in the club replaced the micro on the OpenCM board and reloaded the boot loader.
    [/quote]

    That's pretty hardcore :-)

    I should enhance the power rails on that board for future use, too, aye.
    When it comes to the hubs, OSHPark plus a few SPOX connectors from Digi-Key is a much better option.
    Then you can get as many or few connectors as you want, and some other way of injecting power (screw terminals!) and pin headers for scoping the TTL bus and so forth.

  9. #19
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    Re: Numa V2 - Quad Mech

    Connectors are how Murphy emerges from his evil lair. Consider cutting the connector off the servo wire and soldering all three wires to the board...

  10. #20
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    Re: Numa V2 - Quad Mech

    Lack of strain relief will spell eventual failure no matter the connection type. Those particularly susceptible to a very early failure without strain relief are any connection using cheap wire and any soldered wire connection (solder wicks into insulated wire and makes even the best continuous flex wire fragile at the solder connection). So, yeah, properly crimped contact beats non-crimped board-mount screw terminal any time.

    As for user errors, I recently discovered that I populated a 1k pull-down resistor on a neopixel comm line with a 0.1uF capacitor. Thought it was a software issue, so took a while to fix because I still have not bothered to set up one of my Teensy-3.6 as a logic analyzer. Really should make a thread about that project since I finally have a working 'eye'.
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    bleh

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