Thursday, April 18, 2013

TriBlivion and Sparky

Update2: Sparky2 is available here


I recently built a flight controller board for Tau Labs named Sparky.  It uses an MPU9150 for the main sensor, which combines a 3-axis gyro, mag, and accelerometer which allows tracking the attitude of the airframe.  In addition it has an MS5611 pressure sensor for altitude sensing and control.  One of the main goals for this board were to keep it small and single sided - so it could just be taped onto things.  I also kept three of the holes compatible with the same mounting pattern we have been using so it can easily be swapped out for CC or Freedom.

It has a micro-USB header and 12 PWM in/out pins.  The receiver header breaks out VCC in and 3.3V so it can directly power a spektrum satellite receiver (or in my case an OrangeRX) without an adapter.  There is also a JST-SH header for GPS.  I've already designed a revision with an additional serial port exposed for telemetry as I've become addicted to using my tablet in the field for tweaking.

The first flight tests were quite pleasing

Sparky First Flights from James Cotton on Vimeo.

The smaller frame (Silver Hornet) was using off-the-shelf ESCs so it can't be tuned as aggressively.  The larger one has my ESCs so tunes in really well.  Altitude hold worked quite well - the baro wasn't even covered.

Here is the schematic and code
pdf version:


In addition, ever since I saw the trailer for the movie Oblivion, I really wanted to build something like the aircraft Tom Cruise' character flies.  It has two front motors that can rotate so it can basically behave like a tilt rotor.  I ordered some parts a while ago and they've been sitting around for a while and I finally decided to try and build something similar, which I call (for lack of a better name) TriBlivion.

The front two motors are mounted on servos (using an adapter from servocity to provide some strength).  The yaw channel is mapped to drive each servo in opposite directions to create a yaw torque.  In addition there is an accessory channel mapped to point them both forward to create forward thrust.  I'm really pleased that it stays extremely close to level in this condition with the motors pointed forward at about 30 degrees.  It did need the battery quite far backwards to balance the weight of the servo cages.

I know normal tricopters are meant to have a good yaw feel but I've generally been underwhelmed with my tail servo one.  In comparison this yaw feels EXTREMELY locked in - more than anything else I've flown.

This will hopefully make a really good FPV frame since the camera can be mounted on the front and have a forward view while flying forward.  Of course, it's going to be really important to not get confused since while in motors tilted mode full negative pitch will basically make it stop but you'll be looking at the sky.  This is also just stage one of my quest to build a tilt rotor aircraft and get the best of both fixed wing and quadcopter behaviors.

So here it is flying

TriBlivion from James Cotton on Vimeo.

Unfortunately flying into the fence at the end stripped both servo gears, so it will be a week or two before I get more gears and try it for FPV.

Build list:

  • 2x Servo blocks
  • 2x Hitec servo
  • 3x KEDA 20-22L
  • 3x ESC
  • 2x align 450 size tubes
  • 7x clamping blocks
  • 3x motor mounts
  • cut G10 plate to sandwich motor mounts at 90 degrees


  1. The tricopter is rather fantastic. I like how you have the battery at the back to balance out the design. How well would it work to add a second battery pack, say, 2/3 the way back, for longer battery life? I've never dealt with tri/quadcopters, so I'm not sure how that'd affect stability.

  2. how i would like to see your future versions to have a mounted camera... or a mic... or even payload? :D

    keep up the good work! :)

  3. I'd probably be more inclined to add a larger battery rather than too. It's got plenty of power and little drag though so should be relatively efficient. I had to drop the size of the prop on the back cause it was producing too much lift and hard to keep the tail down. If I went to 10" props on the front it would just be insane

  4. that's nearly idea o mine! Nearly I say:

  5. Hi James. TriBlivion looks good! I have shared it in my blog assuming you don't care:
    With a backlink to your blog.

  6. @flegmatoid whoa that's beautiful. you rendered that? can't wait to see it. Although i did see the amount of differential on the rotors and think it should be yawing like shit. Like the craft in terminator I'm skeptical that would really fly - the motors need to be higher above the center of gravity like the osprey. Very awesome and beautiful though. Look forard to the movie.

    @Anton nope, and thanks for the heads up

  7. Hi james. The main different of this model is the yaw control. In conventional Tricopter we use only one servo in tail motor. Here we using 2 servos in front 2 motor. I would like to made a similar model like you. but i didn't get the flight controller board code. I got only the code for conventional one. So can u share your codes with me if you don't mind. Thank you

    1. The code was just using the Tau Labs code. You can configure the general mixer to do this without issue.

  8. Did you ever get the TriBlivion setup with FPV? I was starting to part out my own TriBlivion and found a few parts no longer available like the servos, tubing, and motors. I figure the tubing could be updated with FLEX500 16mm CF tubing. Could you recommend some substitutes for the servos and motors?

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