I have UHF LRS transmitter from OrangeRX and my last 2 receiver is broken and damaged after several crash. In this article you can build your own DIY Receiver/RX paired with any TX as long as using OpenLRSng UHF. This implementation can be used for RC world like rc car, boat, submarine or drones. These components is cheap and easy to obtain like Arduino Nano and si4432 with max range around 1000m or 1km (unobstructed and no wall). I also use this for fpv on small drones or even on my racing quad. What i like about this UHF is it's very different frequency compared to noisy 2.4Ghz but you also have to check if this frequency (433mhz) is not allowed in your country.
This receiver is not expensive and you can build it from your home using basic tools like multimeter, solder iron and some cables. Right now i build 2 and will add more for my drone racing squad. So let's get started
Step 1: Components/Parts and Tools
(1x) Arduino Nano atMega328 ($2.21)
(1x) SI4432 470MHz 1000m Wireless Module 470M 433mhz Wireless Communication Module
(1x) Heatshrink 5mm with length 350mm
(3x) Small cable with different colors, i pick Red, Black and White or you can add another color like green/yellow etc
(1x) Double Foam tape and (1x) Electrical tape
(1x) Cheap Solder Dekko with 40w including tin with core inside
(1x) IC SOP14 SSOP14 TSSOP14 to DIP 0.65/1.27/2.54mm Adapter PCB Board Converter (4 pcs with just $2)
(1x) mini USB cable
(1x) multimeter to test connection/short circuit
(1x) 3 male single pin header and 2mm heat shrink
Step 2: Making Receiver and Soldering
- Take your IC SOP14 PCB adapter then put electrical tape on the right side to prevent short circuit
- Prepare SI4432 then align with IC SOP4 PCB Adapter, please be careful here, you have to align correctly so it won't mess up. The leg from SI4432 we will attach is number 3 until 9 (from the bottom). Inspect the picture in this section for more detail. Then Solder these legs onto PCB Adapter (look again the picture).
- Now put the double tape foam on the back off our Arduino Nano, then attach our completed PCB adapter to make it firm and not moved.
Step 3: Cables and Wiring
We have to connect between our SI4432 and Arduino, this step will explain about that
There is number from 1 to 7 in pcb adapter and we will use our small cable here, please READ the notes ON EACH PICTURE
Make connection from :
- PCB no 7 to Ard(Arduino) D02
- PCB no 6 to Ard D04
- PCB no 5 to Ard D13
- PCB no 4 to Ard D11
- PCB no 3 to Ard D12
- PCB no 2 to Ard 3.3v
- last, connect SDN+GND on SI4432 to Ard GND (yes, 2 hole combined)
on my picture, you can also see the cables on top of my Arduino. Make sure there is no SHORT circuit on every cable and on SI4432 board. Finally, attach the antena of SI4432 on the far side of the board (look carefully on picture, don't to solder the other pin, that's ground/GND ).
Step 4: Installing OpenLRS Software on Arduino
To use OpenLRS, go to https://github.com/openLRSng/openLRSng/releases
then download software version 3.8.8, unzip that file then open with Arduino Software (if you dont have arduino IDE software download it for free at https://www.arduino.cc/en/Main/Software )
- Connect Arduino Nano with computer using Mini USB cable
- Open OpenLRSng with Arduino IDE
- In Arduino IDE, on menu BOARD, Choose ARDUINO NANO with ATMEGA328
- on menu SERIAL PORT, choose your connection, my case is '/dev/tty.wchusbserialxxxx' or usualy COMxx on Windows
- we HAVE to test if our board (nano + SI4432) is working, the trick is by compiling the nano to TX mode (look at picture). uncomment #define COMPILE_TX 1 then also uncomment #define BOARD_TYPE 5, upload to nano with button UPLOAD. Please wait until you see message 'avrdude done. Thank you'.. please look at log if there is any error. If there is no error you're good to go (don't disconnect Arduino Nano from mini USB cable, just let it there)
- Now let's check if our board working normally for cable connection and the hardware of SI4432. Install OpenLRSng Configurator for Chrome Browser, you can get it here for free https://chrome.google.com/webstore/detail/openlrsn...
- Connect to our Nano with OpenlrsNG, you have to choose the connection first , my case is '/dev/tty.wchusbserialxxxx' or usualy COMxx on Windows then click on CONNECT. After connected go to tab SPEKTRUM ANALYZER, this window is to test if our SI4432 working, if it's working you will see the strength of our board.. but if you can't see the moving graph then please check the connection again, worst case is your SI4432 is fried and damaged (must be replaced).
- After our board is working normally as TX/Transmitter, now we can safely change the mode to RX/Receiver. Go to Arduino again then we will flash as RX. Uncomment #define COMPILE_TX 0 (comment the line #define COMPILE_TX 1) then upload again to Arduino Nano (check the picture if you're not sure). Please wait until you see message 'avrdude done. Thank you'.. please look at log if there is any error. If there is no error you're good to go
Step 5: Finishing and Wrap It Up
For final wiring, there is 2 important connection we must use, one is PPM Out and the other is RSSI (Signal Strength) coming from our Nano. Here is the data from Nano Pinout after flashed with OpenLRSng
D9= PPM Out
VCC = input voltage (max 12v)
GND = Ground for power
we can connect 3 single header pin with PPM, VCC and GND then i tube shrink these to make it neat. For RSSI i just use 1 dupont cable so i can connect that to OSD for connect it directly to our Flight Controller.
This board is very sensitive and fragile to static electricity so we can wrap it up with black electric tape to secure the board, oorr you can use heat shrink too if you have one. Final touch is tubing the antenna with 5mm heat shrink then heat it up with your matches or hot gun.
For binding between TX and Receiver you can look at OpenLRS page here https://github.com/openLRSng/openLRSngWiki/wiki/Ba...
it's not really difficult and i'm sure you can make it too. My second board takes me around 2 hour to make it work.. if you made it just let me know :)