Control Systems

Camera control technologies range from Silly Putty to radio systems -- gather your notes on how to set up the cradle here

R/C rig build and fly video

edited February 22 in Control Systems

Hey everyone,

Here is a video I just finished putting together of the build and testing of my new R/C rig. Those of you who attended the KAPiZoom meeting should recognize it. Well, since then I've finished building it and just did the first test flight the other day. It's working well so far! I hope you enjoy the video.


  • You clearly did an excellent job.

  • excellent workmanship!

  • edited February 22

    Thanks guys! The only issues with it so far are:

    • The FPV camera seems to be misaligned with the main camera slightly. Most of the shots came out with more sky in them than I intended. I need to investigate that and possibly add a shim for the main camera. I'm not sure how that happened, or maybe it's just my imagination.
    • The R/C relay for turning on and off the video feed isn't working when the battery is charged all the way to 8.4V. I have to discharge it to about 7.6V to get it to work. It's not a huge problem, because the discharge curve is nonlinear and the battery still retains most of its capacity at 7.6V, but I don't really understand it. The relay is rated for much higher voltage. I am not an expert in electronics. Anyone have an idea?
  • Looking great! Well done. Agree...need more hands to control everything...especially if you were hand holding the kite line!

    Keep the KAP and KAV coming!


  • Great job, regarding the video downlink, maybe you could convert the HDMI signal out of the camera and therefore you would not need the small FPV camera and add some precision as well as a bit more weight !

  • Very impressive. Regarding the parallax, I notice that the FPV camera is placed higher than the main camera. I guess you try could try sticking the FPV camera directly on to the side of the main camera (just to the left or right of the lens.) Also, is the field of view of the FPV similar to the fov of the main camera lens?

  • edited February 23

    Pierre, I've thought about getting the HDMI directly out of the camera. That would be nice, but it seems more complicated and heavier, so probably not worth it for me.

    dragonblade, for any subject that is more than a few feet away, the parallax effect should be pretty minimal, but I do think I may have a slight angular offset right now, which is a bigger (but still totally fixable) problem. Regarding the field of view, these FPV cameras normally come with an ultrawide lens. I planned this purchase carefully to try to get as close to the same field of view as the main camera. I ended up getting a lens with a 2.8mm focal length to replace the 2.1mm lens that it came with, and that seems to be a pretty close match. It will never be perfect since the aspect ratio is different, but it's close enough. The availability of a replacement lens like that is actually why I got this "mini" size FPV camera; otherwise I could have gone with a "micro" or "nano" size instead.

  • Yea I admit I would be surprised if there were parallax issues at those super long distances typical of KAP. Not something I would have expected.

    And yes, it can be frustrating that most of the little FPV cameras have fisheye lenses. It's good that at least some of them have changeable lenses.

  • Montagdude: I too want to remotely control my FPV camera and transmitter on a rig I am currently building. Will you post a bit more detail about how you did this?

  • rrllewellyn,
    Sure, I use this remote controlled relay:

    To use it to switch the VTx on and off, you need to cut the +voltage lead powering the VTx (the red wire), strip the end of each half of this wire, and then plug them into the terminals on the PicoSwitch. Other than that, you plug the three-wire lead of the PicoSwitch into your receiver, whichever channel you want to use to control it. I use the landing gear channel. See the wiring diagram below. The VTx would replace the lightbulb in the diagram.

  • Montagdude: Thanks, for this detail. On your rig do you use a single power source, or do you have a separate power source for the video transmitter?

  • I use a single power source, a 2-cell lithium polymer battery. I have two sets of leads (parallel circuits) coming off of it, one going to the receiver and the other going to the VTx.

  • Thank you for this additional information. It is my plan to have a single power source, but not having worked with video transmitters on a KAP rig made me second-guess my intention. I am glad to have your experience backing my efforts. There appear to be a number of PWM relay switches available now that I know for what I am looking. I have a while yet before I am ready to fly. But I am in process.


  • edited March 2

    I'm interested to hear how it goes once you get it working. Particularly if the relay is working without issues. As I mentioned above, mine is not switching reliably when the battery is charged above ~7.6 V, even though the spec sheet indicates it should work well above that. That reminds me, I need to put in a support ticket with Dimension Engineering (where I got it from) about that.

  • edited April 18

    I had my first "real" session (not a test flight) with the R/C rig the other day. I got some really nice pictures out of it, especially the one below. Being able to preview the composition and choose when to take a photo is game-changing for someone who's only had AutoKAP before. You do need a steady breeze with few surprises though, since your attention and hands are off the kite for potentially long stretches.

    Here's the session in short-vlog form with some more pictures and video.

  • Great to be able to see your successful launch and resulting photo with your new rig. I post this as an update. I have just finished and bench tested my new rig. I used scrap parts—cut offs from kite spars, scrap aluminum from window casing; a video transmitter and camera from eBay; discarded drawing instruments for the picavet. No 3D printing; all parts are hand cut and drilled. The servos are micro, metal-geared units. The overall weight is 680 grams, more than I wanted. My picavet is the source of more weight than I wanted, but I wanted to build a wide-model of the picavet for experiment, with inspiration from James Gentles. I followed your lead and built in an independent relay switch to control power to the video downlink. So far I have had no issues with reliable control while on the bench; my Lipo provides 8.4 v. (when freshly charged; it is rated 7.4 v.) to the video components through the relay; a voltage regulator drops the 8.4 v. to 5 v. for the RC receiver. Next steps are to launch and test the rig’s ability to fly and operate. I am using a Spektrum DX5 transmitter adapted for proportional pan control, with inspiration from Andrew Newton. The gear switch controls the video components. The Trainer switch triggers the camera via one of James Gentles devices for Canon cameras. Eventually I will want to take the plunge and repackage the transmitter and use an Arduino interface, with inspiration from Dave Mitchell.

  • edited April 20

    Very nice! DIY is definitely rewarding, especially when you get to recycle old parts.

    The people at Dimension Engineering thought the issues with my relay could be due to interference induced in the wiring at higher voltage, which seems possible since everything is packed pretty tightly together in my rig. They suggested some sort of EMF shielding on the wiring and/or the relay unit. I might try that, but I also might just leave it as is, since even when discharged to 7.6V, my 400 mah lipo still has plenty of capacity to run the rig for a whole session.

    Regarding the other problem with the primary (RX0) and secondary (FPV) cameras not being aligned, I added a small shim to tilt the RX0 down by a few degrees, and that fixed the problem. It's still kind of puzzling, because now the two cameras definitely appear out of alignment when viewed from the side, but the photos line up. It seems like the FPV camera must have some sort of optical effect causing that to happen, maybe due to me switching its lens. But it works, and that's what matters!

  • edited May 2

    New rig ground tested. Reliable control at 100 feet. Aerial test soon. On/off video control via a Pololu relay switch. Wish that I could use a smaller gear ratio on the pan axle
    but the micro servo does not give me a full 90 degrees via the Spektrum DX5 transmitter setup. Considering weight change-outs; the picavet is one obvious target. Overall pleased with the project.

  • I purposely designed this rig to be able to switch to portrait mode, and I got to use that feature for the first time today. The posts in the water are the subject. It would have been better if I could have gotten closer (or used a telephoto lens), but I was already wading out into the water as far as possible while holding the transmitter. Anyway, I like the colors and clouds in this one.

  • Just a note to bring closure to my entries in this tread: my new remote controlled rig flew, all systems operated as designed, and I got the results I wanted …!

    Sunset Beach, NC

    Dopero kite made with a flag of Wales, absolutely stable kite, the “wide” Picavet appeared to do what James Gentles said it would.

  • Nice result! Doperos are majestic kites, and especially yours.

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