Doppler Effect

I have been working on a project that uses multiple microphone arrays around the house for presence detection. More about that later when I have something to show off, but in the meantime I thought I would share this as it is very cool and might lead to some interesting SmartApp projects.


Yea, nice. With proper placement this setup gives you the ability to determine if someone is enter or leaving the room… I’ve been trying to figure a way of using motion detectors to do this, this type of sensor would do a much better job of that.

This is such a cool, sciency idea. I love it.

@Mike_Maxwell - as for the motion sensors, Fibaro shows on their website how their hub would do it. Don’t see a reason why you couldn’t do it with a smart app. Scroll down the page to the picture of the person is walking in the door.

It would get expensive though with the number of sensors needed.

I’ve kicking around an idea using a bistatic approach so you could have an AC powered transmitter embedded in a smoke detector like housing (or even integrated) with battery powered receivers.

1 Like

I’m looking forward to the introductin of bluetooth into the Hub V2 :smile:

Hmmm, interesting… decent placement, convenient source of wired power…
The bistatic approach here being each detector having both a receiver and transmitter as in a monostitic configuration, but the results being evaluated bistatically? Wouldn’t that be a bitch to baseline?
NM, re-read, battery receivers, got it.

1 Like

I figured it was doable, device count issues aside, this approach is based on event times, or rather the delta(s) between them, and currently ST’s baseline message processing I think is too variant to work with, or rather around…

Yep… Message times are way to slow in most cases.

Plus i have 2 cases in my home where there are 2 entry ways within 2 feet of each other without a “ledge” to seperate the sensors. The motion sensor idea most likely wouldn’t work for me. I am working on a bluetooth solution but i haven’t had much time so it’s been slow going.

With Hub V2, local app processing should make realtime apps on the hub more doable. You could build a simple doppler motion detector with all of the processing done on an arduino and server messaging times would become irrelevant.

@Mike_Maxwell I was researching another idea when I found this, I read an article about a company that was able to pinpoint gun shots using microphones placed around a city area. With the same approach I should be able to place microphones around my house and determine in 3D space where someone is speaking from. This would give true contextual voice control over your house. You would not even need a sensor package in every area of your house. Standing in the living room and saying “turn the lights on” would produce a different result than saying it in the kitchen, and would not require a complex set of rules or tasker tasks.

3D shot spotting company


The demos on the doppler effect page are pretty astounding. The one that had the most visual impact for me was the one where you moved your hand towards or away from the mic to grow and shrink a box. It’s all happening in real time in the browser using your computer’s basic equipment. Really great.