Harald's Random Stuff

Built a small quadcopter. Receiver from ehirobo, transmitter from Helipal. All quadcopter parts from Hobbyking. It’s fun to build and fun to test. Firmware worked nearly out of the box. Awesome small little wind machine.

The only problem: Instead of using 2900 kV motors I got 2000 kV which results in 32% less rpm, which affects obviously the amount of lift it can produce with the same propellers. Fix: different propellers, more Volt, or more thrust. Right now I need about 85% thrust to lift. Good enough to learn I guess. But new propellers are already on my shopping list (3 blades instead of 2).

Some observations:

1. The yaw gyro axis needs to be reversed.
2. Set P to 50%, I to 0% and P(yaw) to 20% for starter. If you see oscillations, tune those parameters.
3. If I is set too high, there’s a lazy motor syndrome showing: one motor will start very late. But not an issue in flight.
4. A simple 4 channel transmitter is sufficient. More are not used anyway.
5. The transmitter should be in “airo(plane)” mode, not “heli” mode.
6. The cheap and simple KKmulticopter board with only 3 gyros is sufficient and it already beats any helicopter hands down in terms of stability.  At the same time, it does not take away anything else from the pilot as it’s missing all the other sensors some other quad’s have (e.g. barometer, GPS, accelerometer).
7. There are quite a lot of versions of the software for the HK  Multi-Rotor Control Board as it’s KK board compatible. A solid one is the one from Rolf Bakke AKA kapteinkuk itself. I use version 4.7 and it seems to work fine.
8. All those small little screws like the M2 screws for the motor mount, something non-metric and tiny for the prop saver (looks like hex sub-1mm), the 2mm diameter motor axis…I already wish for a larger quad with M3 screws as the minimum size. And it turns out that it would be only minimally more expensive, as small motors are like shoes for children: small does not mean cheap.

BTW, I used yaw by hanging the quad on a long rubber band. Since yaw relatively weak, it did not work well in my hand. I could feel it reacted on me turning it left or right, but I could not really say whether it’s amplifying or counteracting yaw. Turned out it’s amplifying it, and it was very obvious once I lifted the quad into the air on those rubber bands.