Hi. I started flying FPV just recently, on 5.8GHz with cloverleaf on airplane and 5 turn helical on GS. I'm just getting used to camera view so I still fly short range, circles around me, with LCD not attached to my head permanently, just put on car or something so I can check plane visually. I found out that helix has some blind spots here and there if I'm close, and that could be really bad while landing. So I took this idea from Bruce's rcmodelreviews video and build a controller with arduino. It compares RSSI values from two Rx modules and switch according video signal to video output.

Disclaimer:
Everything is provided as is. Circuits provided are not perfect or up to specs (however, they do work). Attemp only if you have some electronics skill (or a friend with skills) and time to test everything. I take no responsibility for anything. It is everyone's responsibility to do proper tests and only use the trusted device.

This is a project in development, intended for recreational use and experimentation. Anyone is very welcome to add hardware or software enhancements

Part list:
- arduino (any will do, I like pro mini, or nano, for their size. and I use cheap clones)
- programming cable if you use arduino pro mini
- 5V relay
- power transistor (I used BD241, but many NPN will do, even 2n2222. For small relays under 50mA coil current, 2n3904 will be okay too)
- 1k resistor
- 1n4007 or 1n4004 diode
- two (or more, depends on circuit version) capacitors 470uF/16V
- 5v UBEC (or some other 5V source)
- two video Rx modules (or RC305 or other video receivers with RSSI output)
- antennae, connectors, cables, project box, hotglue
- stripboard (or you can etch proper circuit board)
- 2n3904 transistor (1 per channel)
- 10Kohm resistor (1 per channel)
- 100ohm resistor (1 per channel)
- 470uF/16V capacitor (1 per channel)
-3xDIP switch or 3 jumpers for channel selection (1pc per rx module)

To simplify the circuits, I didn't include those switches. I assume that everyone building this will read module's datasheet
http://www.foxtechfpv.com/product/5....08-Spec-V1.pdf

I could have used integrated video switch, like one from maxim. But shipping takes weeks and I wanted to fly, so I used a relay. The image is a little darker than without controller because of losses in circuit, but it works okay.

To Do:
- Add LED indicators to show which atenna is active
- Add manual override switch, for testing/troubleshooting
- Add video buffer to enhance picture for use with modules only.
- Add piezo beeper
- Add battery voltage sensing
- Make circuit diagram for use with whole RC305 receivers
- Add video splitter



EDIT:
Dunno If I said this clear, this uses bare receiver modules. But it is possible to use whole receivers like RC305, you just need to solder a wire from modules RSSI pin and route it from inside receiver box into diversity. This could be desirable because ready-made receivers have video buffer inside, and you get better picture this way. You can add video buffer with opamp or maxim chip inside.

There is another version possible: instead if relay and transistor, one can use 74HCT4066 analog switch, like Bruce did. I only could get old chips which have very high resistance, what dimmed picture too much. I encourage anyone to experiment, I'll add alternative schematic and both codes soon.


EDIT:
Added alternative circuit, with 4066. Code for this version not ready yet. Inputs, outputs and controls connected in parallel, to reduce resistance. Chip's pic from wiki




EDIT:
Added new circuit with video amplifiers. Additional parts, per channel:
2n3904 transistor
470uF/16 capacitor
10Kohm
100Ohm resistors
updated parts list

This gives better picture, especially if you use relay and have long cable between diversity and LCD/googles. You can try without amp first and then connect it to compare.


EDIT:
Added new circuit, attachment #4. Includes video splitter at the output. I did simplified schematic with block-like devices, with blocks expanded under the circuit. I hope it is a little easier to read this way.


EDIT:
Circuit for those with whole RC305 receivers + description at:
http://www.rcgroups.com/forums/showp...5&postcount=46

Firmware:

Rename to .ino and open with arduino 1.0 IDE

This is one of the neatest projects I've seen in some time.

subscribed, i start building one this week-end !

Oh god, I come along this evening and open this thread and guess what happens? A few quid come out of my wallet to buy the parts .

Info added to post #1. I'll keep updating it to have info on one place.

I use these ICs in my diveristy controllers and they work great. <$1 as well.

http://www.ti.com/product/ts5v330

I also use these 12V nominal to 5VDC switching regs. I tested about 5 different designs and these work the best (noise wise and effeciency, 90%!!).


http://www.murata-ps.com/data/power/oki-78sr.pdf

I've given this some thought before, but that's as far as most of my Arduino projects go.

Big congrats for putting it together.

I'm really enjoying seeing these great Arduino projects being used for FPV use. Between you and the Arduino DiY OSD we're getting some awesome offerings.

I have a spare LCD module laying around too. Looks like I'll be building one of these this week too

Ill add a piezo with a beep alarm for changing channels as well as Vcc low warning. Pretty much all you need.

Originally Posted by Slaphappysamy

I use these ICs in my diveristy controllers and they work great. <$1 as well.

http://www.ti.com/product/ts5v330

I also use these 12V nominal to 5VDC switching regs. I tested about 5 different designs and these work the best (noise wise and effeciency, 90%!!).


http://www.murata-ps.com/data/power/oki-78sr.pdf

Sure, those are great parts. But I cannot have any of that locally and as I said, I wanted to fly this ASAP, so I used relay . Additional video buffer would really help, but I cannot find a simple one-transistor solution (AC coupled voltage follower?). I added alternative circuit with 4066 chip.

Originally Posted by Slaphappysamy

I have a spare LCD module laying around too. Looks like I'll be building one of these this week too

Ill add a piezo with a beep alarm for changing channels as well as Vcc low warning. Pretty much all you need.

I like that, adding to TODOs . It also could beep RSSI level. Like the more frequent beeps, the lower RSSI is.

Is ts5v330 better than 74HCT4066? So you tried one older than 74HCT4066?

What is the advantage of using these instead of the solution you are using currently?

I made the diy osd, this project is a nice one to start playin' with arduino again.. I've found some other arduino diversity and even tracking projects - mostly in german but we have google translate. I'll try to find the correct link and post it here.

Originally Posted by msev

Is ts5v330 better than 74HCT4066? So you tried one older than 74HCT4066?

What is the advantage of using these instead of the solution you are using currently?

I only could get old CMOS 4066, or HCF4066, which have too high Ron (ON resistance) compared to new ones. (BUT I made it work by stacking 3 chips, to decrease Ron. But I somehow like relay, simple, solid, clicking . For more channel diversity, solid state switches would be more practical, IMHO ) I cannot tell anything about ts5v330.

Advantages? Integrated switches are faster, smaller form factor, eat less energy, no moving parts, no mechanical contacts to fail, maybe less noise. I went the simple and fast way, yet with acceptable results: "make it work with whatever you have " . This could be pimped up with some maxim video switches with buffers, anyone can do that. I wanted to avoid ordering parts from overseas and waiting long weeks for shipping. I might build solid state version later, while flying with this one.

I'm working on some simple video buffers to put inside, to get brighter picture after my 3 meters cable to LCD.

Subscribed. This is one of the best DIY projects I have seen in a while. I fly 5.8ghz on my Slow Stick and have tried both a 5 turn and SPW. I have the same issues you do and I am too chicken to fly the 5 turn without someone nearby to turn it for me.

Originally Posted by cactus

.... I am too chicken to fly the 5 turn without someone nearby to turn it for me.

Yup, same here. And I wouldn't go flyin' without spotter w/ binoculars. Yet . I have 1,2m flying wing for fpv, but I'm considering something smaller, under 1m, on 2 cell, that I could fly alone short range.