The mQX trained me for flying quad copters but my real motivation around getting into multi-rotors was to record video, then find a way to do FPV (first person video), and eventually integrate sensors with an open source platform for autonomous flight. I’m a software engineer so the autonomous flight really intrigues me though I am a long way off from that.
I figured the best way to start is to fly something that will work well off the shelf. I went ahead and bought a standard DJI 450 Flamewheel with the Naza flight controller from Addictive RC in Tucson, AZ. The Naza-m flight controller is a little expensive but I think it is well worth the money. The flight control software is fairly advanced, which stabilizes flight, and it has intuitive software to configure it. The other open source flight controllers seem good for people who may want to customize but I am mainly concerned with stable flight right now. I’ll probably get into the open source platforms later when I want to integrate other systems (think arduino).
I built the 450 according to spec with no modifications. I didn’t have a lot skills in this area except for the fact that when I was 13 I built some RC cars. I had to learn basic soldering techniques and watch a few YouTube videos showing the 450 build step-by-step. The documentation was sparse so the videos were immensely helpful. All said and done I had the 450 built in about 6 hours over a few days.
I flew it a bit and adjusted the gains according some posts I found about the subject. It always seemed really stable to me so the gain adjustments I don’t think did that much. The gains will stabilize the copter if there are oscillations while it is flying. There are videos out there demonstrating what happens when the gains are set really high or low and the oscillations are very obvious. These gains are going to depend greatly on the weight of all the equipment. Out of the box it is super stable.
One thing to note: don’t adjust gains inside. I broke a few props because the copter was facing the opposite direction I thought it was, which resulted in a crash right into a coffee table. Ouch.
I then proceeded to try different video recorders mounted to the front. The first was an Easy Clip 720p video recorder. This device was very light so it was a good place to start. The initial videos were very shaky and had lots of jello.
I assumed there are multiple forces at work here.
My solution was an aluminum plate glued to the front with some silicone glue. This must have provided some dampening because after I wrapped the video recorder in foam and electrical tape I got fairly decent video. The video recorder itself was dropping frames since it was cheap so I decided it was a good first attempt.
Onto a camera upgrade
I did some research on camera types and what is best for moving video, image stabilization and frame rates. I decided I wanted a CCD sensor camera for the next attempt. The advantage here is the sensor records video by capturing the image all at once using a global shutter instead of a rolling shutter which leads to jerky video if there are vibrations. Check out these links to see what I mean:
- Panasonic DMC-TS4 CCD Camera Analysis - Notice the jerky video for the CMOS sensor
- B&H Photo Description of CCD Versus CMOS - Explains how the sensor reads in images
- DPPhotoReviews.com DMC-TS4 Specs - Full specs for a CCD camera
A few things to note here. DP PhotoReview is the best place to get camera specs. You can get sensor sizes, field of view and frame rates supported. I figure a CCD is smoother so you are better off using it in a cheaper camera since the CMOS cameras that take really good video are pricey and heavy. These are not an option for a quad. I think the CCD is the best value for the money plus my wife happen to have a Sony DSC-W560 that she won at a company christmas party. How convenient for me.
The Sony DSC-W560 has about a 1/2″ square sensor size which is decent. It only takes 720p video but I don’t mind that. The kicker here is it does SD video out as well all for about 124 grams plus a cable. I think this camera landed in my lap and was meant to be.
My first attempts at recording video with the Sony had a lot of vibration. The camera wasn’t dropping frames but I need a new damping solution and the foam wasn’t going to cut it. I found a build it yourself hanging camera platform on RCExplorer.se for a tri copter using piano wire. I thought this was brilliant (and cheap) because it separates the camera from the copter frame and also puts the heavy batteries on that platform so it has more mass therefore making it more difficult to vibrate. Check this blog out I think David Windestål is one of the most innovative FPV guys out there and he has detailed build instructions on everything he builds. An inspiration for all of us.
David has a CNC tool so he can build things a bit easier than the rest of us. So I decided to use aluminum for the camera platform. This worked out ok but I decided balsa wood would be lighter than aluminum and easier to work with. I also saw the FPV Manuals QAV400 used these rubber/silicone dampers in the frame to isolate a platform from vibration. I decided to integrate these into a second small platform for further dampening.
Here is the initial video I tool with this new double-vibration damping platform.
The wire platform provide decent results with the Sony DSC-W560. I don’t think the double platform provided any benefit since there was not enough weight on the second platform to provide any damping. The props make a big difference. My next post will be a new platform using only the rubber dampers from FPV model. I like their concept of dirty and clean platforms so I’m going to roll with that for a while and compare.