I find it hard to believe that you can buy a little radar-based motion detector for less than a quid (definitely don’t buy these off Amazon as they are at a rip-off price compared to AliExpress). And it’s especially difficult to believe that it works with no problems! As you can see from the image, I’ve soldered a few headers onto the board so that I can plonk it onto a breadboard. I think my soldering station needs a new soldering tip as the solder kept rolling around the header. The solder eventually settled and took, but I was scared I was going to fry the board with the 360 degree heat from the soldering tip. I just left a time gap between soldering each header to let it cool down before moving onto the next one.
The first thing I did was to see whether I could get it working with an Arduino, and it couldn’t be any more simple. Check this page: RCWL-0516 microwave radar motion sensor for Arduino test and review for details. In essence you actually only need three pins for this to work. You need ground and vcc obviously, and then you just need to connect the ‘OUT’ to a pin on your Arduino. I believe you can attach the OUT pin to a PWM pin on the arduino, but I just attached it to pin 8 (a straight digital one) because that was good enough for my purposes. I uploaded the sketch (from the website link above) to my Arduino and sure enough, every time I moved, it triggered the LED on pin 13 on the board. I used a 10 k resistor on the OUT pin, which is overkill I think, but it was the only one I had to hand as I really didn’t want to go trawling through everything to find one. I think you’ll be able to use a resistor with a much lower value than that. In fact, I’ve read other articles where the author hasn’t used one at all.
Anyway, the next thing to do was to see whether I could power an ATMEGA328 from the 3.3v pin on the RWCL board. According to this link https://github.com/jdesbonnet/RCWL-0516, you could get 100ma over this pin. Only one way to find out! I set up the ATMEGA chip as you would normally do on a breadboard (there’s plenty of tutorials how to do this on the Internet, just Google it), and linked it to the RCWL board, with digitial pin 8 going to the OUT pin as before. Again I managed to get the LED on pin 13 to light up.
The next thing to try was to see if I can get a NRF24L01 chip running with the same set up, and after a day of trial end error, I managed to get a transmission working through my existing set up. Just need to refine the sketch now, but at least I got it working with the NRF chip which I wasn’t expecting to work given the small amount of power available from the 3.3v pin.
Will give a further write up and illustrations once I have done enough work on this to know it’s reliable.