Last night I unpacked my new MultiWii controller and plugged it into my PC. I bought it from Hobby King and it comes ready to fly out of the box – configured for an X-quad, which is perfect for my carbon H-copter.
The Multi-Wii board attracted me because it comes with so many sensors out of the box. Barometric pressure, compass, gyros and accelerometers as well as the option to add GPS in future. That’s compared to just gyros on the KK board. I love the KK board to bits – it’s a great board for line-of sight flying, allowing a fair amount of acrobatics and some nimble and fast flight. It’s scary flying FPV with the KK though. I managed a good FPV flight at the weekend (see video later) but it would be great to push more of the stability control onto the ‘copter for less stressful remote piloting.
I didn’t get the board hooked up to the quad or the receiver last night, just plugged it into the PC and fired up the Java tool.
I have to say I was very impressed with the board and the UI tool. The tool shows a live trace from all of the on-board sensors and a 3D model of the ‘copter which moves in real-time. Every single setting is configurable, including the PID terms, throttle travel, behaviour of the auxiliary “switch” channels and so on.
Hardware wise, the barometric pressure sensor was the star – it responds to changes in height of about 10cm, which is spookily accurate! The only worry I have is the effect of wind on this sensor – I am wondering whether a wind shield is going to be needed for breezy days.
Down sides so far: The GUI is a bit painful to use. About 25% of mouse clicks are ignored or lost (I think because the refresh loop for the graph is running and the app is polling for user input). Also, the numeric values are editted using very very very small sliders. It would be much simpler to just enter the text! Maybe these things annoy me more because I do that sort of thing for a living…
Expect more soon! In the mean time, here’s an FPV video from this weekend…
While repairing the crash damage to the Carbon-Copter I decided to do a more scientific investigation into the differences between carbon and aluminium…
10mm x 10mm Carbon square tube weighs about 0.5g/cm while aluminium bar of the same dimensions (purchased from B&Q) is just slightly under 1g/cm. That makes the maths easy – 150cm of bar needed for the carbon quad means a 75g difference between carbon and aluminium – which isn’t that bad.
Aluminium is cheaper and seems to be more crash-resistant too, plus I can pop over the road at lunchtime to buy some as opposed to ordering it from China. So, I made up a complete set of parts using each material.
With the ‘copter repaired I concentrated on setting up the FPV gear. Sadly, I broke my little FPV camera – I think I caught a screwdriver on some of the components and shorted something. It was only a tenner but I am still quite cross with myself for not taking enough care.
Anyway, I have the GoPro which can also output video for FPV use. There’s a slight lag (less than half a second probably) in the video feed which makes it a bit weird and since I’m not willing to drill the waterproof case the camera has to fly “naked” which is a little riskier. On the plus side, many people report success with exactly the setup pictured below:
The garden isn’t the ideal place for testing with fences and walls in every direction, but my darling wife was kind enough to snaps some pics of the video feed on the garage telly while I had a nose over the neighbour’s fence flying line-of-sight.
The feed was a little noisy but a lot of that is going to be due to the fact that the signal had to get through the garage roof. Penetration is not good on 5.8GHz signals. Need to sort out something a bit more portable and pop over to Dr J’s house for more testing this week. Watch this space!