The Ardupilot platform is a nice open source autopilot and stabilization system. It can be used in a variaty of airframes, so I decided to install one in my new No.1 flying wing. Why did I choose the APM?
- It is a reliable and highly customizable system
- Offers a completly customizable OSD (minimOSD)
- It is affordable (80$ for a miniAPM with OSD, current sensor and NEO-6M GPS [at least for china clones])
For now, I did not pay attention to the autopilot functions of the APM, I just use the “ACRO” stabilization. But still, the large amount of functions that can be configured by the user come at a price: the APM has a very steep learning curve, even if you just want to use basic functionality. It took me quite some time to get everything running smoothly. So this will be the first article in a small series where I will try to summarize how I set up the APM.
The first thing that you need to figure out is how to power everything without getting a nasty ground loop or having the OSD flicker like hell when you fire up your ESC ;) So this is what I ended up with:
Actually it is pretty straight forward. The diode between the boost-buck and the LC-filter is important to prevent them from forming a resonator. I adjusted the Boost-Buck’s voltage to compensate for the voltage drop over the diode and the LC-filter, that way I get constant 12V to power my FPV gear.
The only thing that took some experimenting was how to power the minimOSD. On my board, ground of the 12V and the 5V side was already connected. So make sure not to connect ground on both sides, otherwise you’ll end up with a groundloop. The first thing I did was modding the OSD following this guide from flitetest (it’s easier to just connect one power source instead of two). My initial plan was to power the OSD from the 5V side only, so on the 12V side I would just connect the two video lines. But that didn’t work out so well, every time i started the motor the OSD began to flicker and/or was barely visible. It turns out that connecting power on the 12V side, in addition to having the 5V mod in place so that the 5V side gets powered by the stepdown of the 12V side, works just fine.
In the next post I will cover how to connect the miniAPM with the RC gear (RX and servos) in more detail.