Yet Another Arduino-based KAP Transmitter - with Hover Rig

edited November 2016 in Control Systems
Some of you may have noticed this album of photos on Flickr of a KAP transmitter and rig under construction. I've now added a page to my website giving (much) more details.

The TX uses an X1TX0 r/f board extracted from a Spektrum DX4e transmitter. This is a full-range board, unlike the 'park-flyer' X10EMTX board I used in my previous TX but is programmed in exactly the same way (using the serial output pin of the Arduino). The KAP controller also has a Hover switch, since my new EOS M rig has Hover capability (a first for me). It also has a 5.8GHz video downlink (another first).

The page has downloadable wmf plans for the transmitter box and rig, as well as a downloadable Arduino 'sketch'.



  • Hi Dave,

    simply GREAT and always a positive surprise,... well done

    SMAC from Italy
  • edited November 2016

    Really useful stuff, my confidence in the project is growing. Having repackaged a transmitter (at hefty expense) in an industrial enclosure

    I was gutted to find I'd killed the radio range. The enclosure forms the counterpoise to the Tx antenna and I'd ruined that.

    I wonder if you have conducted range tests with the set up you describe?

    I tend to find my rig a huge distance down wind on Bft2 days and that's when the range limit finds me out. I have improved things a bit by using a proper Spektrum Rx with carefully positioned antennae but I reverted to an unmodified DX5e which seems to work fine although it's bulky and fragile.
  • No range test yet, but I plan one soon. The DX4e range is supposed to be at least 1000' (300m).
  • Hi Dave,

    Well done on your new KAP transmitter - it looks like a labour of love, as these things are meant to be!!. Your code looks well commented and as such should provide a useful tutorial to other Arduino fans like me! The use of a serial data stream rather than PPM is also very interesting and something new to me.

    Hi Bill,

    I’ve dismantled a few 2.4 GHz antennas and found that they are generally ground independent and do not require an external counterpoise.The common antenna arrangement uses an internal coaxial counterpoise in the form of a skirt which attaches to the end of the coaxial cable’s shield, leaving a quarter wavelength of bare coaxial inner conductor to act as the radiating element.

    I wonder if you have a transmitter or coax cable problem. Do you have a way of measuring the transmitter output power at the antenna connector? I’m lucky enough to have an ancient HP power meter, but there are a few low cost items which might work available on ebay these days:

  • I've pulled apart a number of 2.4GHz rubber ducky antennas - and can confirm Al's comments.

  • For various reasons Ive not been able to do much testing of the new TX and rig. However I did manage to do some ground-based tests today. Everything seems to work fine, at least at a range of 20 feet or so! The video is very sharp and there's no interference at all between the 2.4GHz rig control and the 5.8GHz video. The little GTeng video receiver is now velcroed to the TX box (I've removed the wrist strap).

    I've added some photos (and a very short video) to the Flickr set here. Sample photo below.

  • Congratulations Dave! Very neat...looking to see it airborne!

    Intrested to see how the GTeng reciever holds up with 200m+ range. BTW which 5.8Tx are you using with it?

    Getting the oportunity to fly when we are beset by short days, high pressure, fog and lightwinds takes some patience. . but if you get the chance this is the season of low light and dramatic shadow.

    Seasons greetings from the fen.


    ps fixed my range issue with a tweaked Rx antenna.
  • edited December 2016
    Hi Bill - I'm using this video transmitter. Very small and very cheap (somewhat over-powered though). The other (minor) snag is that, like all the video TX's I've come across, it needs 12v. I'm using a little Pololu converter to turn the 5v from the 4AAA pack into the 12v the TX needs.
  • At last I managed a real-life test of the TX, rig and downlink - a brief visit to Paignton sea front about 6 miles from home. As usual the sun was directly behind the kite making life difficult, but everything worked perfectly. The rig was never much more than 150' away, but video reception was excellent and despite the small screen quite sufficient to aim at largish targets.

    You can see a few of the resulting shots here.

    PS I forgot to test the HoVer switch! Next time ....
  • Success!

    I was looking at your EXIF data and am curious as to what settings you employed. Aperture was either f/7.1 or f/8, ISO was consistent at 100, and the shutter speed was 1/200sec to 1/320sec.

  • A bit of a cock-up Kevin. Somehow the Mode Dial of my EOS M had been switched to "Scene Intelligent Auto" (A+) without me noticing. Not sure what effect that had on exposure etc. It's now back to standard Still Photo P mode.
  • Classic. I've done that dial 'trick' several times myself!
  • I've added pages describing the AutoKAP version and the continuous panning servo version of the transmitter (and updated the main page to point to both of them).
  • edited August 2017
    I have built Dave Mitchell's autoKAP version and it's a real boon.
    I can now launch the rig and switch an autoKAP sequence on and off at will and revert to a directed camera on the same rig. For me this is a wonderful way to work!

    There's some refinement to come but Dave has opened the door for a new way of exploiting the kite lofted oportunity. Of late I have been flying more auto than directed because of wind, time and saftey constraints it's lovey to be able to 'take back control' of the camera in mid sequence.

    At the transmit end:

    The receive end is a 2 servo RC rig, here it is with the controller in a box:

    I have a simple push button ( to the left of the pan rocker ) to switch modes.

    What's great about this is the 'generic' RC set up: no modification of the rig is needed to have it respond to the auto sequences.

    The only drawback to the project is the availability of the RF units, they turn up on ebay occasionally but otherwise they have to be hacked out of Spektrum/ Horizon Hobby Txs.

    First flight results are here:

    Thank you Daves, Wheeler & Mitchel!
  • Hello guys,
    i would like to build the tx autopan Wheeler & Mitchel but i can not understand if the resistors and cip MCP23008 must be mounted in the cabling, see this 36464772665 / mount without how explained in qua, I also tried to load the KAPTXAuto360Z firmware of Mitchel with arduino 1.6.4 but I got a text error .. i have to load the libraries, i'm wrong?
    Thanks for help Dario
  • Dario

    don't build that design. Both Bill Blake and I struggled and never got it to work. Instead build the version described here which doesn't use the MCP23008 or the Wire library.

    Both of us have had a problem with the trim pot in the new design but the resistors work fine. We are both using a 360 servo that has a trim pot attached instead. I'm still trying to understand the trim problem and will be updating the source code in the next day or so.

    I'll also try to put together instructions on getting the libraries installed - the new design just uses the dsm2 and bounce libraries.

  • Thanks Dave ,i'll let you know after the assembly works.
  • Dario - I've revised the page about the AutoKAP TX - the zip file has been updated to include the revised sketch and there are photos of the construction here and a video of my EOS M rig being AutoKAPed here.

    As far as libraries are concerned, the page here tells you how to add one - you should only need to add the bounce library (by pointing at the The DSM stuff should get compiled when you compile the main sketch.

    Note that you will have to add the SparkFun Pro Micro 3.3v 8MHz board to the list under the Arduino's Tools/Boards menu. You do this by going to the Arduino Preferences menus and add the following URL to the "Additional Boards Manager URLs:
  • edited September 2017
    It might be useful to note the latest Arudino IDE version (1.8.2) now compiles the sketch.
  • I've re-organised the pages describing my AutoKAP TX, its simpler KAP TX cousin and the EOS M Rig they both control. I've also added a page of construction notes on the AutoKAP TX.
  • thanks Dave
  • edited September 2017
    I got to fly with the AutoKAP Tx on Friday after a long wait for wind and light I ended up flying in marginal conditions. The kite would rise, pull well and then drop back in sudden lulls. I decided I'd risk the rig hoping I could haul line fast enough to keep things aloft. Not an ideal situation at all but I thought using auto mode I might get lucky.....

    and so it proved to be. I was able to switch to auto once the rig was at a reasonalble height and use manual when the kite was at its apex. The manual shots were pretty tame but I was happy to confirm 'point and shoot' was working.

    I was able to stuff the Tx into my pocket when things got tricky as I have re-built it into a smaller case:


    I got about 250 shots and this,completely un-expected, capture:


    Having the option of camera control method does indeed increase opportunity!

  • hi guys, could you use the arduino nano instead of the micro pro or would there be problems with the 5v current?
  • The r/f transmitter board needs 3.3v, which the micro pro produces at VCC if you supply 5v to the RAW pin. Looking at the Nano spec, it seems it too has a pin that outputs 3.3v, so it should work fine.

    Of course you will have to make sure the Nano is in the Arduino IDE Tools/Boards menu, but I think it's there by default (unlike the Micro Pro).
  • Hi Dave, I have a few questions to ask ... how do I binding tx rx? In the components list there is a 5K potentiometer for what is needed, why the choice of 10K tilt potentiometer? thanks
  • Binding is described in the "Binding" section on this page. It's very easy.

    I put a 5k pot in the list because that's what I had used in previous transmitters but for the latest tx I had a 10k one lying around. Either will do fine (a 10k one will drain the battery less). I didn't buy any of these pots - they cam out of the r/c transmitters I have cannibalised over the years.
  • edited February 2018
    If it helps here is the parts list I used for my latest build:


    I found some parts are quite rare as I wanted the most compact configuration possible. Most of the switches are surface mount, the slide pot for example Is really hard to find in short lengths.


    I have used this on 3 flights now and find it is really the best remote I have used so far. Being able to operate in auto and directed modes is a massive step forward. A bigger screen would be nice and the 1 hour runtime on it is limiting but the convenience of its size wins.

  • Thanks guys, I'm starting to assemble everything, I'm trying a box made with the 3D printer, the problem of the spaces of the components, forces you to keep certain measures my hour is 140x70x35 but I have to enlarge it a bit even the cradle I printed in 3d just ready I'll show you .. Bill in the list you have to add a power bank for emergencies ..
  • I can not upload the photo..??
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