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Thread: AP Cinetank-L / Pixhawk build

  1. #1
    Navigator TalonSix's Avatar
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    AP Cinetank-L / Pixhawk build

    A couple guys asked for some setup details on my AP Cinetank-L build in another thread, so I figured I'd just start another dedicated build thread instead (Mods: maybe we could get a subforum for Flying Cinema build threads?).



    So first off I will warn you that I am not in the running for the Wire Management Achievement of the Year award with this build. The downside of running a Pixhawk is DF13 connectors (which are very secure but are a pain in the a$$) and there are cables, cables, everywhere. Plus I need to learn how to make my own custom servo cables to cut down on some of the clutter. I've been through dozens of config tweaks since I initially assembled this aircraft since I'm a firm believer in the "If it ain't broke, fix it anyway" philosophy.

    So for the hardware on this tank:
    - Cinetank L frame
    - Cinegimbal
    - Afro PDB
    - Castle 25A quadpack
    - 3D Robotics Pixhawk flight controller
    - 3DR GPS and compass
    - T-Motor 4008s for the main motors
    - T-motor 2208 gimbal motors
    - GetFPV 32-bit Alexmos gimbal control board
    - FRSky X8R receiver
    - ImmersionRC 600mw VTX
    - 3DR 900 MHz telemetry radio
    - DPCAV 2-channel Video switch
    - SurveilZone Sony 960H CCD Effio-V 800TVL Ultra WDR Camera w/ 2.1mm Lens
    - Generic 5v to 12v stepup
    - 3D Robotics MinimOSD
    - Prop of the week: 12" APC MRs
    - Lumenier 4200 4S pack

    I’m sold on the Castle Quadpack. The ESCs are built extremely well and are very compact. They come in packs of four with one ESC having a built in 5v BEC. This powers the servo rail on the Pixhawk. From there the servo rail powers the X8R.

    This tank comes in at AUW 2044g. I get approximately 12 minutes of flight time and have had this tank out to 1000m where the RSSI drops to below where I'm comfortable. Although I'm confident in the Pixhawk's RTH, I don't want to find you what happens that far from me. The Pixhawk has some superb features for AP and holds GPS lock better than my VectorTank.

    The flight camera from SurveilZone is amazing with incredible color detail. The DVR pixellates it more than it appears on my ground station monitor, but this will give you an idea of how it looks:




    So onto the tank...

    Top view. The VTX is getting direct unfiltered power off the PDB as recommended by Sassen - zero issues with interference.




    GPS mast folded down


    Right side showing the 3DR radio. I start to lose telemetry at about 600m with this setup.


    Right side underside of the top plate. You can see the 12v step-up covered in liquid electrical tape to the left of the 3DR Safety Button. Behind the safety is the video switch.


    Left side view. The Alexmos board is in that black case on the front of the aircraft. It's getting unfiltered power directly from the PDB. These new boards are designed for this kind of abuse.


    MinimOSD attached to the top plate. The six-pin Pixhawk connector faces aft, so all I need to do to adjust the OSD is remove the six-pin connector with a pair of tweezers and attach the six-pin USB cable. You do a lot of this on-again-off-again business if you obsess about the location of every little piece of information on the OSD. Guess how I know.


    The underside of the tank. The guys at Flying Cinema sold me a set of the old tall landing gear bases so I could get a little more standoff than the stock landing pads provide. I don’t like the looks of the aircraft with the tall landing gear little stubby legs, so I just run these without the legs and it works great. You can also see the 3DR buzzer in the center of the dirty section base.



    Minor gripes with this build:

    • The front four anti vibration balls are partially squished under the weight of all the stuff I have on the front of the aircraft.


    • The X8R RSSI output is supposedly PWM, but it doesn’t read accurately on the Pixhawk. At first I thought it might be a MinimOSD problem, but Mission Planner is seeing the same garbage readings. I found a thread on the other forum where the unwashed masses are certain that it has something to do with the X8R’s firmware. It’s okay though since the X8R automatically sends RSSI to the Taranis, so I just have that let me know when the RSSI goes below 35%. It’d be nice to see it on MinimOSD, but I haven’t figured that one out yet. You can see on the flight camera still above where the RSSI shows 99% when the Taranis was reporting somewhere around 80%.


    • The clearance between the left front prop edge and the GoPro output is tight. 12” props will actually whack the GoPro line out if the camera is pitched forward (found that one out the hard way too). Note the damaged GoPro plug. I’ve got a flat one coming from China, so that should solve this problem.




    Overall, I love flying and tinkering with this machine
    Last edited by TalonSix; 30th October 2014 at 09:48 PM.

  2. #2
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    Fantastic thread. Thanks so much for making the effort to post it.

    As I mentioned previously, this is almost identical to the setup I want to run with so it's great to see what works and what could be better.

    A couple of questions, if I may:

    i) I note you've got your pixhawk mounted on some foam. Was the vibration dampening insufficient on the frame?
    ii) You mention powering your VTX (and assumedly camera) directly from the PDB. What does this mean from a minimOSD wiring point of view?

  3. #3
    Navigator TalonSix's Avatar
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    I mounted the Pixhawk on the foam blocks before I knew any better, but it also helps with wire management. I run a bunch of the cables that have to go from the clean frame to the dirty frame through the cavity created between the blocks underneath the Pixhawk. For what it's worth, on my other tank the Vector is mounted directly on the base of the clean frame with double-sided tape only.

    I'm not certain what you mean about "from a wiring point of view", but the chain from the VTX to the camera looks like this.
    VTX -> 12v stepup-> camera switch -> MinimOSD -> flight camera

    The Pixhawk also provides power to one side of the MinimOSD. As I understand it however the camera side power simply passes through the board whereas the FC side provides the operating juice.
    Last edited by TalonSix; 31st October 2014 at 09:35 AM.

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    Quote Originally Posted by TalonSix View Post
    I'm not certain what you mean about "from a wiring point of view"
    As I understand it, you shouldn't use ground from PDB to the minimOSD's video side as it creates a ground loop and may burn out. I believe it was built with the expectation of using a separate battery for the video side but I, like you, hope to avoid the complexity and weight it would add.

    I believe it's possible to solder a jumper set to share a common power but am not clear on setting up such a solution.

  5. #5
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    How's the cinegimbal for you? I bought one and I'm not impressed. It really bothers me that there is no adjustment for balancing. It's sorta close with a bare gopro 3, but if I want to use a layer lens and plug in my live out cable the balance is way off and can't be adjusted. This is a major oversight IMO

  6. #6
    Navigator TalonSix's Avatar
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    Quote Originally Posted by lowdonkey View Post
    How's the cinegimbal for you? I bought one and I'm not impressed. It really bothers me that there is no adjustment for balancing. It's sorta close with a bare gopro 3, but if I want to use a layer lens and plug in my live out cable the balance is way off and can't be adjusted. This is a major oversight IMO
    I'm happy with the Cinegimbal, but it's my first gimbal so I have no basis for comparison.

  7. #7
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    look good, looks a lot like both of my L's with pixhawks. mine are messier than yours! (i have video switch for gopro & ccd cam and being pissed off because u have to destroy the DF13's to ever remove them, I got mad & cut every one in half & added huge connectors so i can disconnect wiring when needed LoL!) all of my gear is put on 1/4" thick open cell foam & then glued to the frame with PU. ugly but works fine. pixhawk is a great match for these big frames, big props & big batts.

    love that you can see the current average throttle output too. really lets you know more accurately where batteries are at during the flight & shows you how prop changes effect the craft.



    on both of mine i have the radios all on the top deck. as long as i put my laptop 3dr radio up away a bit i get telemetry past a mile LOS.
    be careful with the folding mast. remember both the gps unit & pixhawk have a magnetometer, but the prefered one is the one in the GPS unit. maybe not, but i could see an issue over time where the calibration is lost. if so, maybe consider using the pixhawk internal one. <3
    Last edited by Toysrme; 2nd November 2014 at 11:04 AM.

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    Quote Originally Posted by lowdonkey View Post
    How's the cinegimbal for you? I bought one and I'm not impressed. It really bothers me that there is no adjustment for balancing. It's sorta close with a bare gopro 3, but if I want to use a layer lens and plug in my live out cable the balance is way off and can't be adjusted. This is a major oversight IMO
    I mentioned the very same thing about balance when I was asked to comment on the prototype plans. I was told it was better for plug and play if there were no options. I can't see how a gimbal can work well with a live out cable hanging off of it and no way to re-balance it. Same goes for a layer lens or polarizer. I guess stick on lead works....

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    Pixhawk Settings

    Quote Originally Posted by Matt- View Post
    As I understand it, you shouldn't use ground from PDB to the minimOSD's video side as it creates a ground loop and may burn out. I believe it was built with the expectation of using a separate battery for the video side but I, like you, hope to avoid the complexity and weight it would add.

    I believe it's possible to solder a jumper set to share a common power but am not clear on setting up such a solution.
    Can I ask everyone what "frame type" in arducopter people are using with thier Cinetanks? When I use the PX4 flightstack, all is good, but if I try to load Arducopter in an X configuration, the Tank rolls to the right and tries to fly away. Any help would really be appreciated.

  10. #10
    Navigator TalonSix's Avatar
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    Quad X. I barely had to adjust the presets, but I'm using a Pixhawk. I don't know if that makes any difference.

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