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Thread: DIY Arduino-Based 3-Channel Diversity Controller

  1. #1
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    Cool DIY Arduino-Based 3-Channel Diversity Controller

    Hey Folks! Long time lurker, first time poster here. I wanted to share with you the diversity controller I've been working on for the past month or so. I originally got the idea for this build when my buddy purchased a couple of very basic diversity controller PCB's based on the LM324/CD4066 schematics I've seen floating around here.

    I wanted to take it a step further by driving the multiplexer with a microcontroller instead of an opamp comparator so that I could draw a visual readout of signal strength to a display and maybe implement calibration features later. I based the RSSI signal amplification section off of IBCrazy's programmable diversity controller.

    Here's the final result



    This was my first time using Eagle and I had never etched a PCB board prior to this project so I'm totally open to suggestions if you see something I should have done differently.

    Parts List:
    • 3x 10uF Eletrolytic Caps
    • 2x LM358N Opamps
    • 1x NTE1966 Voltage Regulator (or equivalent)
    • 3x 120K Resistor
    • 6x 51K resistor
    • 3x 100K trimpot
    • 1x 20K Resistor
    • 1x 22 Ohm resistor
    • 3x 330K Resistor
    • 1x Arduino Pro Mini
    • 1x 74HC4053 Multiplexer
    • 1x Samsung KS0107 / KS0108 based LCD display


    Schematic:
    http://mattcarpenter.github.io/schematic.sch


    Board:
    http://mattcarpenter.github.io/schematic.brd


    Source Code:
    https://github.com/mattcarpenter/rss...ity-controller

    Build Process:

    Obtaining an "RSSI" signal from the ReadyMadeRC 2.4GHz video receivers was not a trivial task. The receiver modules do not have an RSSI pad to solder to on the edge of the board like others do, so I had to locate the AGC pin on the Zarlink SL1461SA FM demodulator chip. I fried a few of the demodulator chips as I was poking around but found a distributor in the United States that sells them. If anybody needs a SL1461SA or two, PM me. I've got about 26 extra because the minimum order was $10 and the chips were about 35 cents a piece.



    Prototyping and figuring out the multiplexer's truth tables



    Screen works!



    I probably went through four or five boards before I got it right. I made stupid mistakes such as etching and then discovering a mistake in the schematic, reversing the top layer and bottom layer transparencies, not printing the artwork to paper first to verify everything was to scale, etc..



    This board was the best looking of the bunch but the printer scaled the artwork in one direction which messed up the pin pitch



    Ran out of ferric chloride because of all the botched boards I was etching. I had some muriatic acid and hydrogen peroxide laying around from another project so I tried etching with cupric chloride. Worked quite well.



    Final board with a few components already in place



    Complete! I discovered later that I forgot pull-down resistors on the RSSI inputs so I ended up adding them to the RSSI input pin headers. Also made a mistake with the multiplexer so I had to add a couple jumper wires to reconfigure the video inputs.



    DIY angled connector on the LCD display



    I'm using RCA connectors for both video and RSSI input. The chuck on my $70 Harbor Freight drill press wobbles so I had trouble lining up and drilling even holes.



    I replaced the audio connector on my RMRC receivers with "RSSI" from the AGC pin on the FM demodulator



    All together

    Last edited by pizzapiepeet; 1st March 2015 at 03:47 PM.

  2. #2
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    That is very nice.I love the screen showing the relative strength of the signals.
    Most of the money I made this year I spent on FPV,the rest I just wasted.

  3. #3
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    so awesome! now start production cause i wanna buy one lol edge around the lcd screen tho. maybe CNC route it out, or 3d print a bezel & then mould it with silicon & cast your own bezel, or 3d print the case & then mould/cast others.


    ya itd probably just be better to cast your own plastic case as long as you're not having to overly heatsink anything.

  4. #4
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    Quote Originally Posted by Toysrme View Post
    so awesome! now start production cause i wanna buy one lol edge around the lcd screen tho. maybe CNC route it out, or 3d print a bezel & then mould it with silicon & cast your own bezel, or 3d print the case & then mould/cast others.
    Yeah, the edge is pretty rough. I used a nibbler to cut out the LCD screen "window" but it didn't do so well through the thick aluminum. I'm in the process of assembling a 3D printer so a bezel might be a good first print

  5. #5
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    nice. my rostock max v2 stays printing 24/7 at this point lol

  6. #6
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    Nice, what case is that??
    Rusty
    NEFPV^

  7. #7
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    Quote Originally Posted by Rusty105 View Post
    Nice, what case is that??
    Hammond Manufacturing 1455K1201BU. Really nice enclosure; my local electronics store sells them in several different sizes and colors.

  8. #8
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    Wow, how great is that?? Awesome post!
    What screen is this? What program did you use for the pcb?

  9. #9
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    Quote Originally Posted by stupsi99 View Post
    Wow, how great is that?? Awesome post!
    What screen is this? What program did you use for the pcb?
    Thanks! I used CadSoft EAGLE to design the PCB and the screen is a QC12864B (Datasheet). Any 128x64px LCD display with a KS0108 and KS0107 should probably work. I'm using the u8glib graphics library on the Arduino and it's able to drive the LCD using an I2C interface.

  10. #10
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    really great job my friend we have build the board but we have problems with uploading the code to arduino (we are begginers with arduino programming)if you can help us with this we shall be grateful thank you

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