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Archive for July, 2013
Posted by grmis | Jul 13, 2013 @ 03:09 AM | 28,184 Views
Here is a simple & very cheap DIY RSSI video diversity. It is based on an Arduino Pro mini (less than 4$ on eBay) and the following video switch from Hobbyking: (less than 6$)

One advantage of using this video switch is that almost no external component is needed. The video switcher is supposed to be connected to an RC receiver, but here the PWM signal needed to select the video source is generated by the arduino. I just added one push button to select one particular receiver, or the automatic mode (the one with best RSSI), as well as a 2 leds to indicate which receiver is actually selected, and what is the RSSI level (bar with 5 leds). This can obviously be extended to 3 receivers instead of 2. The system is powered by 5v taken from (inside) one of the receiver (here the 12-channel VRX sold by HK, 0.9-1.2GHz). I am using one ground plane antenna on receiver #1, and a patch antenna on the other (both from IBcrazy's design). I confess that I have not yet used this in the field... but on the bench everything looks ok

If needed (?) I could post the detailed schematics & arduino code.

Warning: some labels on the video switcher are incorrect ! Remove the cover to see the correct pin labels on the PCB.

EDIT (July 26th): I have done a few test flights with this diversity system and it works . I however noticed that some care is need to calibrate the two RSSI levels, even though the two video receivers are (in principle) identical. Their RSSI levels seem to differ a little bit and this must be take into account in the arduino code. I may add a potentiometer to be able to adjust "manually" some bias in favor of one receiver/antenna or another (at present I have to change the calibration parameters in the code -- which is not very convenient if you are on the field).
Posted by grmis | Jul 08, 2013 @ 04:05 AM | 12,893 Views
Here is a video of my first attempt to fly with someone else doing FPV :
FPV duo: Dynam Hawk Sky following a Swift wing (3 min 0 sec)

Detailed setup. There are a few new things (highlighted in red) compared to my previous video:

- Plane: Dynam Hawk Sky / 2400kv motor [Hoffmann magnetics] & 6x3 prop / Turnigy Plush 40A ESC / 2200mAh 3S turnigy nano-tech.
- Flight controller: CRIUS AIOP v1 (HK clone in fact) + ArduplaneNG r303 + minimOSD (extra 2.2)+ uBlox Neo6 + Airpseed sensor (used for autonomous nav. modes, such as loiter or RTH).
- Video TX : 900MHz / 200mW. Antennas: DIY inverted-V & ground-plane (video link is ok up to ~1 km at least)
- Camera: Sony 600TVL CMQ1993X (from sc2000, with IR filter), 2.5mm lens.
- RC RX: 2.4Ghz FrSky D4R-II in PPM mode, PWM RSSI connected to the CRIUS board through LC filter (& displayed in the OSD). Although I think I have calibrated it correctly, you can see that the RSSI indication sometimes still shows " 99% " at a few hundred meters
- Recording (on ground): SD DVR from Hobbyking. Initially I was very disappointed by the video quality of this DVR, due to huge & numerous artifacts. Then I realized that it was a codec/viewer problem: I switched from VLC under linux to media play under windows, and now the quality is much better
- Remark: During this flight I learned that in FBW-B mode with ArduplaneNG, the elevator is inverted (thanks mkuvy).

Same flight seen from the other plane (Swift wing) :
Premier DUO FPV (2 min 9 sec)