Your garden variety motion detector uses IR, but these days, there are fancier technologies for achieving similar goals. If so desired, you can source yourself a microwave-based presence sensor instead. Indeed, like [N-08 Labs], you might like to whip one up into a basic intrusion detection system.
The idea is simple enough—take a RCWL-0516 microwave presence sensor, and set it up to detect motion and warn you when it happens. It’s a simple part to use—it simply drives a 3.3 volt logic output high if it detects someone or something. It basically just emits a microwave signal and detects a change in phase when someone or something—usually something fleshy—is in front of it. [N-08 Labs] simply hooked one up to an IO pin on an ESP8266, with the microcontroller board set up to communicate wirelessly with a Blynk IoT app, which then in turn fires off a smartphone notification that the sensor picked something up. The whole thing is built inside the shell of an AC adapter that provides power and let it easily hide in plain sight.
A project like this doesn’t just have to be for security purposes. You might even just use it to determine when your pet (or a racoon) is using the cat door, or similar. Indeed, we’ve seen great solutions to that particular problem, too. Video after the break.
This is pretty cool. The IR based ones don’t seem to detect mice: they’re too small. This may do better, although as I recall, microwaves have a wavelength in the same order of magnitude as the size of a mouse, so it may also struggle.
2.4 GHz has a wavelength of about 12.5 cm (~4.9″), so that would be some pretty big mice. I have not used a “RCWL-0516 microwave presence sensor”, but I suspect that they detect changes in phase, so maybe it could detect a mouse. Only one way to know for sure would be to test it (possibly by rolling eggs in front of the sensor at different distances).
If trying to sense the whole barn floor probably not, if sensing closer in a baited space which triggers the death zap at the critter though. Score! Shawn Woods knows simpler ways to score big in mice caught. In small places nothing beats a Victor loaded with cashew nut jammed into the bait clip, that’s my weapon of choice. Trapping let’s you keep score and no poisoned vermin dying outside spreading the poison. Zero is the best score in this game after some rounds.
Quid of the consumption of a mmWave radar vs a PIR sensor? In this case, the stuff is plugged, which means it’ll fail if AC is cut from outside. But if it’s run from a battery, how long can we expect to work?
If I remember correctly, rcwl is 3mA to run, some low range pirs are in the uA range
Kicad design files for the used radar, would be cool to make esp32 board with integrated radar.
https://github.com/jdesbonnet/RCWL-0516/issues/37
There are also some information about reading analog baseband signals from the radar to extract more information (speed, magnitude, distance…).
If the modules can be used to extract more information from the received signal, I’m definitely interested in learning more. I wonder if it’s possible to use two and modulate the transmitted signal.
Microwave motion detectors have been around for decades. They bring their own problems like seeing through walls a little too well. Often, they are paired with a PIR sensor to reduce false alarms.
PIR sensors do very poorly in rooms with forced hot air or mini splits; they see a plume of heated air as motion.
Microwave might indeed do better, but I’d want to be able to tune it to ignore cats. Directionality might not be enough given that cats climb.
Seeing thru walls a bit wouldn’t matter much for home security applications, though it might for home automation.
I wish I could be tuned to ignore cats
Ignoring animals is a done deal, Honeywell/Ademco sells/sold a PIR/Microwave motion detector that is indicated to ignore animals up to 60 pounds. Have only tested it with cats, and have not had a false alarm in 15 years of use.
Seeing through walls is a problem for security applications if it is an exterior wall.
Another issue with PIR is when the air temperature rises to around body temperature, they stop sensing people or animals. Our PIR outside lights are useless in the summer.
I don’t really like this. Cats are usualy the only criminals around my home :-) Just wait till someone figures out how to train them to fetch valuables…
I haven’t tried it, but I read that the microwave signal interfaces with the wifi signal of any esp module, especially if placed close together and gives a false signal. Is that true?
With a sample size of 1, I can say that mine does not. The motion detector is at the other end of the room from my access point, and have had no issues. That might be because the motion detector also uses PIR, don’t know for sure.
Is Hackaday short of stories or what ???
This is old news…….
The RCWL-015 has been around since before 2019 and there have been done numerous projects with it.
I like the form factor of cheap microwave motion detector in ac power brick tho… that’s new for me.