Android First Person View
It looks like, that now (2013-08) most components are available to build a low cost FPV (First Person View) system with Android Smartphones.
* Viewer The Viewer could be an actual smartphone with a minimum screen resolution of 800 x 480 pixel and WLAN. In order to have a good contrast view under all circumstances (e.g. sun light), some kind of goggle is needed.
* Video Camera The Video Camera could be an older smartphone with a minimum screen resolution of 800 x 480 pixel and WLAN. Unfortunately the program (Android App) WiFIFPV needs actual Android version >= 4.0.
* WLAN router In order to archive a good transmission distance, an Ad-hoc WLAN is not sufficient. You need a WLAN router to connect the two smartphones.
If you do a double click on the pictures, they will be shown in a larger dimension.
The FPV viewer is a smartphone HTC Evo 3D with:
- screen resolution: 540 x 950 pixel
- Android version 4.0.3
In order to look at the video display without disturbance of the sun, you need some kind of goggle. I found a proposal to build a simple one with card board, see links and the pictures.
The proposed fresnel lens from the link does not have a very good optical quality. So I changed it to a personal optic:
a pair of personal computer glasses and
a standard reading glasses with 3 dioptric
The elastic strap for the head is glued to the card board with hot glue.
The cut out on the bottom is needed to operate the smartphone, when it is in place.
Because the magnification of the glasses is not as strong as the proposed lens from the link, I had to elongate the goggles by about 40 mm.
The view program is the app FPVviewer, which is easy to use.
Unfortunately the video frame rate is just 4 fps (frames per second).
For a test this goggles are sufficient, but for a more serious application you should build a better setup.
FPV Video Camera
I do not want to risk my new smartphone flying in a model aeroplane, so I used an old one, a Samsung Galaxy S I9000.
Unfortunately the free Android app WiFiFPV does not stream a video with the last Android version 2.3 from Samsung. But with the help of Cyanogenmod version 10.1.2 (or CM10 = Android version 4.0) video streaming is now possible.
Compared to a normal video streaming app, WiFiFPV has the advantage, that it uses the position transducer from the phone for an artifical horizon, and uses GPS. The On Screen Display shows the following informations from top to bottom:
- Speed in km/h
- Distance from home in m
- Altitude in m
- Number of seen satellites for GPS
- Heading, valid only if the speed is not zero
WiFi RSS in dbm (Received Signal Strength)
- Video Frame Rate in fps (frames per seconds)
FPV WLAN Router
Important for this portable operation is a low power consumption. Fortunately there exists in the internet a list which shows the power consumption of polular WLAN routers. The lowest power consumption (1,5-2,1 W) is found at the WLAN router Edimax BR6228nC.
In order to get portable use, you need a +5 V power battery supply. The best efficiency and low cost is achieved with a car USB power supply adapter (about 4 EUR). The USB plug is cut off and a plug compatible with the router is soldered to the cable. On the car 12 V plug a connector for a 3 cell LiPo battery is soldered, see picture.
To achieve a good range a self made Yagi Antenna is added. The second factor is the modulation. From the data sheet you found:
Output: 11n: 15±1dBm, 600 Mbit/s 11g: 15±1dBm, 54 Mbit/s 11b: 18±1dBm, 11 Mbit/s (netto maximal 50 %) Sensivity: 11n (40MHz): -68dBm, 11n (20MHz): -71dBm, 11g: -74dBm, 54 MBit/s 11b: -87dBm, 11 MBit/s (netto maximal 50 %)
So I selected modulation 11b for a good range.
List of pages in this category:
-- RudolfReuter 2013-08-27 17:13:04