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Yvon's KAP rig #4
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.
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.
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:
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.
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.....
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.
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