HOWTO – APM power distribution

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:

APM_power

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.

first impression of Xiaomi Yi

At first, this short test video was not meant to be public, because we plan to do another review including also the SJ5000+ but I think this short “test” already shows the quality you can expect from the Xiaomi Yi cam, as long as the focus is correct (if not, you can easily open the front of the cam, remove some hot glue spots that holds the lens in place and refocus it).
Here is the link how to to change the lens focus:  https://dashcamtalk.com/xiaomi-yi/#Out_of_Focus

Although Youtube uses some strong compression on their encoding-settings, you can still see, that the Yi is much sharper than the Mobius and even the GoPro 2. Even the whitebalance is more natural then the very warm colors that I get with my GoPro2.

Xiaomi Yi – cheap alternative to popular GoPro Cams?

We used the GoPro Hero 1 and GoPro Hero 2 (which are identical to the GoPro Hero 3 White / Silver when it comes to image quality). The new GoPro 4 silver/black cams are really great but we don’t need 4K Video or very good low light quality, especially not when we need to pay for those goodies 380€ / 480€.

That’s the reason why I still use my old GoPro 2 and Leo has bought the SJ5000+ and I ordered the new Xiaomi Yi.

At the moment I think the most interesting HD cams for FPV pilots with a smaller budged are:

– Mobius / Runcam HD
– SJ4000
– SJ5000+
– Xiaomi Yi

All of them have some pros and cons which are:

Mobius
+ lightweight
+ nice and aerodynamic form-factor
+ cheap
– battery life
– 720p 60fps pretty bad
– a little slow when it comes to fast changing exposures

SJ4000
+ fits in GoPro Mounts/cases
+ cheap
– strange colours (oversaturated blue sky)
– 60fps mode is a lie

SJ5000+
+ good image quality and true 60fps 1080p Mode
+ display (although this is not important for me)
– slightly bigger than GoPro / SJ4000, so it might not fit in every GoPro Mount/Housing/Gimbal
– battery life
– colours (whitebalance is much better than SJ4000, but still not on par with a GoPro)

Xiaomi Yi
+ cheaper than SJ500+ but pretty similar image quality
+ good white balance
– many Yi cams are slighty out of focus (details in higher distances might be a little blurry)
– not compatible with most GoPro Style Housings/Mounts/Gimbals (slightly bigger than GoPro 3/4, exactly like the SJ5000+ and besides that the Lens positions and size is also a little different)

My Xiaomi Yi arrived today and after some research I decided to remove the plastic front and some hot glue that hold the lens in place, so I can change the focus on the lens.

Xiaomi_open Xiaomi
After that modification, my Yi has a brilliant sharpness and it easily beats my GoPro 2 in almost every situation (same mediocre low light performance, better framerates/modes, sharper/better Image Quality, lighter etc.)

We will upload some footage from our cams (GoPro 2, Mobius, SJ5000+ and Xiaomi Yi) so that you can decide, which one might be the best for you.