Yvon's KAP rig #4

edited January 2013 in Control Systems
Hi all,
I started designing a 4th KAP rig using a small remote control from a Linx Technologies evaluation kit that I bought 8 years ago. This will finally allow be to control the rig remotely after 8 years of autoKAP. The evaluation kit is still available from Linx Technologies but it is slightly different.


I'm building the whole control circuit on the receiver's prototype area. So far, I have my design on paper and I started soldering the sockets for the ICs (MSP430 microcontroller and 2 stepper motor drivers). The sockets are translucide and I put some LEDs inside. On power on, the microcontroller LED will turn on and each motor driver LED will turn on when the stepper motors are powered and moving. The LEDs won't be visible in the air but since I'm designing it, why not do it with style. LOL :-)


I will post my progress on this thread. Feel free to comment and suggest any idea. This will help me refine my design but will also help others that want to build their own rig.


  • edited January 2013
    This should be awesome! Ground up KAP remote, instead of using airplane controls and servo/camera interface devices. The linx technologies website is interesting too. Good luck.
  • Hi,
    Here's a first draft of my schematic (Large copy here).

    On the left side, D0 to D7 are the signal lines coming from the Linx receiver, one for each button on the remote. D0 to D3 are read directly with the microcontroller. D4 to D7 are converted into one analog signal that the firmware will decode. I had to do this because the microcontroller didn't had enough pins to read them all.

    Upper right, these are the two stepper motor drivers. The LEDs are connected to one phase of each motor. When a motor is moving the LEDs will blink alternatively.

    Below that, the interface to trigger the cameras. For the Canon A590i, I'm planning to use a SDM script to trigger on the USB power. For the T4i, there's a remote input connector which only needs two signals pull to ground; one for focus and the other one for the trigger.

    Finally, at the bottom right corner, this is the power supply for the video transmitter. I want to control it remotely so I can save battery power when the rig is in autokap mode. I can turn it on once in a while to make sure everything is ok.

    This is a draft and I still need to test a few things to make sure it works as expected before I can solder everything together on board.


  • One thing that I forgot to mentioned is that this circuit can also be used to drive servo motors. Only the firmware in the microcontroller has to change.

  • I'm almost done building my new rig. I'm just waiting for my PeKaBe blocks. I'll try to post photos soon. In the mean time, here's how I programmed the 8 button remote control. I'm open to suggestions:

  • SWEET!

    Man, I can't wait to hear how this works out. I LOVE the size of the components in this system. Perfect for travel, hiking, backpacking, or just a stroll along the beach.

  • Some here's some photos. I'll try to take photos outside this week. Surely I'll have a chance to KAP during the Dieppe (Canada) festival this week.

  • From the pictures this is an amazing piece of work and electronics. I for one would be interested in greater detail about the rig and the electronics if time permits.

  • I'll try to add more details after this week as I'll be busy at the kite festival here in Dieppe, Canada.

    The schematic that I posted above has changed a little. I will post and update when I have a chance.

    One thing that i forgot to mention is that this rig was designed to fit my Canon T4i as well. I did all my testing (in my basement) with the T4i.
  • Hi all,
    Here's an update. I had a chance to use this new rig several times during the Dieppe Kite festival (Canada). Everything is working well except that the remote control can only reach about 100feet so I used the AutoKAP mode most of the time. Under 100feet, the remote is usable.

    When I tested this remote control evaluation kit, I could reach more than a 1000 feet with the receiver inside my house and me down the street.

    As I was suspecting, the video transmitter is causing a lot of noise on the 3.3V supply voltage powering the remote control receiver even if the video transmitter is connected to a separate battery pack. This is probably because of the prototype circuit that I built is picking up some noise through all the wires. I will try to shield the remote control circuit in the next few weeks and see if I can get more range.

    I didn't had a chance to try my Canon T4i yet. The wind was either too light or too gusty during the festival.

  • I added a filter on my receiver's power supply rail and I changed the video transmitter power harness (Red and black twisted wires on the photo) for a coax cable. Now, the 3.3V for the receiver circuit is clean, no more noise caused by the video transmitter.

    But, my remote control range is still limited. The next thing I'm suspecting is the aluminum frame behind the receiver board. I think the L shape at the bottom might be disturbing the receiving RF signal. I will do more tests this weekend. More to come.....
  • Hi all,
    A ran some tests this weekend by moving my control board (which includes the remote control receiver) away from the KAP rig and the remote control range was still limited.

    I checked some signals on an oscilloscope today and didn't find anything obvious but based on my observations, I think I can improve the range by tweaking my firmware in the microcontroller. I already started but it will take several days before I can get to a point to do further testing.

    In the mean time, I can still use my rig in AutoKAP mode or with the remote control if the rig is within a 100ft from me.

    Also, I already started to take some notes for a new rig design, similar to this one but lighter. For examples,

    1. I can replace the two vertical aliminum plates by two custom made electronic circuit boards. The bare circuit board could be the same on both sides but with different components assembled for each. One side will be assembled with the remote control receiver and the control circuit and the other side will be assembled to supply the power to the video transmitter. By merging the electronics, a big part of the wiring and the 2 aluminum plates, I could save probably at least 60g to 100g.

    2. I have another remote control circuit that I can use which is lighter and uses a smaller antenna. This would save me another at least another 30g or so.

    3. I'm plannig to replace the 4 AA NiMH batteries with an equivalent LiPO battery which will save me another 30 to 60g. Actually, I can easily do this on the current rig.

  • I updated the firmware in the microcontroller and I was able to control the rig up to at least 200 feet and this is having my rig inside my office and I was outside in our business neighbor's parking lot. I'll try it on a kite line this weekend if the weather permits.

    There are more changes I want to do in the firmware that will take a little longer to implement but it looks promising.

    Also, this morning, I sent an email to Linx Technologies tech support with a few questions to see if there are other things I'm missing causing the remote control range to be limited. They are claiming up to 3000ft range so obviously there's something that can be done. I just have to find what. :-)
  • Here are a few more photos with my T4i camera. I haven't had a chance to actually fly with this camera yet. I'm hoping to try it soon.

    The rig alone weighs 698g.
    The whole rig with the Canon A590IS camera weighs 929g.
    The whole rig with the T4i camera weighs 1406g.

  • edited January 2014
    I was not satisfied with the limited range of this remote control so I moved forward to a more recent technology: XBee module from Digi International.

    I did a first test today at work (during my lunch hour of course lol). I could control my rig in our boardroom from my office PC. This is about 30m, going through about 3 walls and whatever other obstacle.

    I will try further distance from home this weekend assuming we don't have another snow storm. Since mid-December we've been having on average about 1.5 snow storms or rain per week. We have received almost 2m of snow and 120mm of rain in the last 6 to 7 weeks.

    If this works, I'll have to design/build a remote control. It will still be fairly small but bigger than this one I used above.
  • Cool!

    Is it the 1mW or 2mW module, or perhaps XBee Pro with 10mW?
  • The ones that I used are 2mW but I have access to 10mW if I have to.
  • edited January 2014
    Rig #4 looks good!
    You could probably save quite some weight by using thinner metal sheet and aluminum rivets...

    What X-bees do you have? Are they 2.4Ghz? I have never heard about the 10 mW type, I have 2 XBee-pros (just to be sure) for my rig #6, but these are 60 mW. I have not done serious range tests yet... My guess is that placing the radio module in or near the metal frame might reduce range...

    Let us know when you have done outdoor range tests, very interesting!

    PS: I use an arduino as controller and can update the firmware over the radio, which is cool :-)
    KAP rig controller with Arduino Fio and XBee Radio
  • I tried the XBee modules and I was able to get a little more range up to about 250 feet but this is not as much as I wanted. I have XBee-Pro modules on order. I should get them next week. In the mean time, I managed to put my new remote control together.

    Here are some photos:
    - I used Pololu boost/buck regulator to convert battery voltage to 3.3V:


    - I manage to fit the electronic board, the batteries and the XBee module into a box that I had to slightly trim

    And here's the assembled remote:
    A = AutoKAP mode
    M = Manual mode
    V (black) = turn on video transmitter
    V (red) = turn off video transmitter
    C (black) = Camera takes photos continuously (every 3.5seconds)
    C (red) = Stop taking pictures
    White buttons = (only in manual mode) move camera up, right, down, left and the middle one is to stop any motor if the rig missed the "stop" command when one of the motor moving button was released.

  • edited February 2014
    Went for a KAP session today with my new remote control and a pair of XBEE-PRO RF modules.

    The KAP rig was at about 400feet and I could control it. I could see that sometime I had to press a few times the buttons for the command to go through. I'm suspecting the aluminum frame is not helping. That's one reason I started a 5th KAP rig with less metal parts as possible. I'm heading with 1.5mm thick fiberglass (used for electronic circuit). I'm hoping to see an improvement with the remote control range but still, 400ft is enough for me for now.

    After about 10 years of autoKAP, I can finally point the camera where I want.

    Now, I have to finish this new 5th KAP rig and work on the display on the ground. I have a hi-res lcd that I want to somehow attached to my arm with possibly the remote control circuit integrated. This way, I'll have my hands free for kite control.

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