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Thread: Malum IK

  1. #21

    Re: Malum IK

    No pictures. I spent most of the free time setting up development for the Teensy I'm using, and configuring servo IDs and parameters.

    I'm using PlatformIO, with Visual Studio Code, and it can target Teensy just fine (there's a pre-made plugin to do so.) And, boy, is it a better IDE than Arduino!

    The board you see in the picture above, is a board I made a while back, to have something that interfaced with DXL bus, and a MOSFET for a gun, and some 5V and 3.3V regulators, and some other misc I/O (LEDs, place to mount Xbee, soft power, buzzer, arming circuit for the gun FET, etc.) At the time, I was thinking I might try something with two legs and a body/turret, so only three DXL connectors on it. As it is, it comes in handy for this build!

  2. #22

    Re: Malum IK

    I lied! There are parts I had made but not taken pictures of. Specifically, the side brackets that both mount the scoring plates, and serve as cover holders for the battery tray. They screw into the sides of the feet that also serve as holding brackets for the battery tray.

  3. #23

    Re: Malum IK

    Moved over the gait generator, and tuned it for the new measurements and servo orientations.
    Also built a bracket for holding the gun, and brackets for holding the PCB, and mounted the RC receiver. You can see the pigtail antennas sticking out from underneath.

    It's not quite walking by remote control yet, but I think I'm less than an hour away from that.

    It's going to come down to gun build, and to a lesser extent camera build, now. I can slap one of those super cheap widescreen self-contained cameras on the nose of the gun, worst case -- there's power out headers to tap into for that. I'd love something better, but a working worst-case solution exists.

  4. #24

    Re: Malum IK

    Btw, those tibias are really quite long, giving the bot a wide gait. Great for speed and perhaps reducing tilt, but there are some narrow spaces in the arena ...
    Another "if I get the time" thing: I'll reduce the tibia length by about an inch or so? My IK code is all parametric so that's an easy change there, although I'll probably also need to reduce the "stroke" of the gait. Maybe increase the frequency instead.

  5. #25

    Re: Malum IK

    Looking good!

    Are you using a Teensy 3.2 to run the IK code? I'm using a Teensy 3.5 in my mech, I haven't had a lot of luck running the dynamixel bus at a high baud rate. I'm running mine at a 250000 baud rate, wondering what you're running.

  6. #26

    Re: Malum IK

    I'm running a Teensy 3.2, and I run at 1 Mbps. The trick is to have a good, strong driver chip ...

    I had to look high and low to find one that was a "very good" match to the TTL bus, because the default 74HCT125 ones require additional logic to invert one-half of the buffer state. I ended up with a TC7WT241FU, which is an old obscure chip from Toshiba that I'm assuming will go obsolete any day now ... but while I can get it, it's been working great! This is the second board I'm using it on.

    In other news, when the 3D printer just isn't precise enough, and you have to hold everything in a rectilinear set of vise jaws (I don't even have a sine plate,) there's SOOO MUCH CAM to do!
    Cut one of each of these parts today, but had to scrap them for various reasons (only one of which was putting in the wrong tool at the wrong time.)

  7. #27

    Re: Malum IK

    @jwatte - Cool chip - May have to try that one out... I have used two different chips with one (125/126?) which worked... I also used a chip similar to the one you mentioned, but it was larger as if I remember correctly it did 8 IOs, where 4 where on inverted and 4 wher on the not inverted... But that one took up a lot of room!

    The 125/126 circuit looked something like:
    Click image for larger version. 

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    Sorry for the not overly clear image...

  8. #28

    Re: Malum IK

    That looks like it should work, at least in theory ... Although I prefer to have some small resistor in series, to reduce the slew rate a little bit.

    Also, that power bus on/off MOSFET construction looks oddly familiar :-)

  9. #29

    Re: Malum IK

    This part. THIS PART.

    If we go out for beers next week-end, ask me about this part.

    Actually, better not. It's a sad story and probably no fun to hear.

  10. #30

    Re: Malum IK

    At least I didn't break a tap in it when tapping it after this photo.

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