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Thread: PhantomX controlled by a Raspberry Pi

  1. #21

    Re: PhantomX controlled by a Raspberry Pi

    I ordered a couple of 3' versions from Amazon.com, may shorten a few of them by hand... Probably not the best way, but should hopefully get it up running without a having them a mile long

    Kurt

  2. #22

    Re: PhantomX controlled by a Raspberry Pi

    Quote Originally Posted by KevinO View Post
    I found 6" usb cables online last week. Let me see if I can find them again. I was thinking of buying a few usb plug breakout boards and just making my own length. I haven't had much time this week to make any progress. We have a new movie coming out on March 22nd so we've had allot of events and wrap parties here at the studio so I've been distracted a bit.
    Forgot to ask (if you don't mind), which picture?

    The three foot cables arrived, which are still obviously too long. I have cut down one to size so far, sort of following the ideas in the http://www.fixup.net/tips/usb/index.htm guide... Liked the idea of offsetting the solder joints as to not have to individually wrap each internal solder joint. My first one did not isolate enough as the insulation melted some. But hopefully I got the intersections wrapped enough to keep from shorts. This one is about 1' long
    Click image for larger version. 

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    Next up to see if it still works.

    Kurt

  3. #23
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    Re: PhantomX controlled by a Raspberry Pi

    The movie is called "The Croods." It's about a prehistoric family that goes on a road trip to an uncharted and fantastical world. The underlying message is about how parents, although to a child seem over bearing and over protective, has a responsibility to protect and educate. (Well that's what we have on the summary page of the script explanation.) So I found a interesting hub that I bought on an impulse. I haven't tested it but hopefully it'll work. It's a "squid" type hub so I don't need any cables if I just want the length it gives me. Click image for larger version. 

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  4. #24

    Re: PhantomX controlled by a Raspberry Pi

    Looks like a nice find. I have played around some and now have everthing so it does not trip over stuff

    Also uploaded a few images... Still not sure best way to load these on the forum...


    .Click image for larger version. 

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    But is shows the SSC-32u on one side and the Raspberry Pi on the other side. I have the Pi attached to a prototype shield board I had fabricated earlier, so it's mounting holes fit the standard Lynxmotion/Basic Micro/Orion Robotics hole patterns. Also on the T-Hex I have the LifePo4 battery, the UBEC down to 5vs, the small USB hub and the XBee... Pardon the dust on the brackets.

    Still lots more I can do to pretty it up but at least is is now self contained

    Kurt

  5. #25

    Re: PhantomX controlled by a Raspberry Pi

    Which LiFePo battery? I've looked for a good 4S LeFePo to avoid the 16.8V max voltage of a LiPo, which causes MX Dynamixels to complain about overvoltage for a minute until it goes below 16V.

  6. #26

    Re: PhantomX controlled by a Raspberry Pi

    I am using a 2s Zippy 3600 30c series battery. I am using it with standard servos (HS-645mg). So far the servos are all still working, even though the normal voltage is 6.6v versus the 6v of the Nimh I normally use. But it is also my understanding that the high voltage (right after the battery is charged) is about the same or about 7.2v

    Kurt

  7. #27
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    Re: PhantomX controlled by a Raspberry Pi

    So I wanted to give an update. I was sidetracked tonight experimenting with different leg setups trying to come up with a 4dof leg with the brackets I had. After seeing Tyberius's Envy I settled on this leg design while I was switching back to 3dof leg. I have everything put back together now and ready to shoot another video. Sadly it's getting late and I have jury duty tomorrow. So no late night for me. The top has to come off again for more drilling so that is why I only have four screws in the top plate per servo. Anyway here is what it looks like currently. (I have a tendency to tweak and play so it might change.) Due to the Pi and the servo power supply the battery is now relocated to on top.

    Click image for larger version. 

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    Last edited by KevinO; 03-19-2013 at 02:52 AM.

  8. #28
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    Re: PhantomX controlled by a Raspberry Pi

    I picked up that wifi dongle you posted about. Is it still working for you? I was getting tired of the legs tripping on the network cable. Also last night I came up with a simpler way to calculate the servo speed instead of using that function from robosavy you played around with back in your development with the phantomX. I simply found a factor that I multiply the angle difference of the curPos and goalPos by for all three joints.

    Code:
    int ServoDriver::CalculateAX18MoveSpeed(int wCurPos, int wGoalPos, int wTime)
    {
      int wTravel;  // Angle amount of travel
      int factor;   // Factor to calculate speed 
      int wSpeed;   // Speed value to return for packet creation
      
      // find the amount of travel for each servo
      wTravel = abs ( wGoalPos - wCurPos );
    
      factor =  pow ( wTravel, 2 ) * 2.93;
    
      wSpeed =  factor / wTime;
    
      if (wSpeed > 1024) wSpeed = 1024;
    
      return wSpeed;
    }
    It's not perfect on the very highend or very low end but it works rather well in the middle. I'm trying to track down a "glitch" at the moment. Every once in a while I see a leg jerk in it's movement. Usually when I reverse movement... For example from a full forward to a full reverse. It's very odd. I'll have to throw in some printf statements to see if it's actually in the angles or if it is a packet glitch.

  9. #29
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    Re: PhantomX controlled by a Raspberry Pi

    Quote Originally Posted by KevinO View Post
    It's not perfect on the very highend or very low end but it works rather well in the middle. I'm trying to track down a "glitch" at the moment. Every once in a while I see a leg jerk in it's movement. Usually when I reverse movement... For example from a full forward to a full reverse. It's very odd. I'll have to throw in some printf statements to see if it's actually in the angles or if it is a packet glitch.
    See if the leg jerks correspond with a clear pattern of odd packets, perhaps? PyDyPackets should work well for logging this and plotting servo positions.

  10. #30
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    Re: PhantomX controlled by a Raspberry Pi

    So I decided to remove the case on my usb hub to save space. I shrink wrapped it to keep the wires secure.

    Click image for larger version. 

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