Smart Occupancy Sensor Knows All

In the last few decades, building engineers and architects have made tremendous strides in improving the efficiency of various buildings and the devices that keep them safe and comfortable to live in. The addition of new technology like heat pumps is a major factor, as well as improvements on existing things like insulation methods and building materials. But after the low-hanging fruit is picked, technology like this smart occupancy sensor created by [Sina Moshksar] might be necessary to help drive further efficiency gains.

Known as RoomSense IQ, the small device mounts somewhere within a small room and uses a number of different technologies to keep track of the number of occupants in a room. The primary method is mmWave radar which can sense the presence of a person up to five meters away, but it also includes a PIR sensor to help prevent false positives and distinguish human activity from non-human activity. The device integrates with home automation systems to feed them occupancy data to use to further improve the performance of those types of systems. It’s also designed to be low-cost and easy to install, so it should be relatively straightforward to add a few to any existing system as well.

The project is also documented on this GitHub page, for anyone looking to build a little more data into their home automation system or even augment their home security systems. We imagine that devices like this could be used with great effect paired with a heating device like this, and we’ve also seen some other interesting methods of determining occupancy as well.

32 thoughts on “Smart Occupancy Sensor Knows All

      1. How about you only switch on the mmwave presence detection once a PIR sensor detects motion and gave the sensor turn itself on once nobody is detected anymore, to “sleep” until the PIR detects motion again.

  1. Years ago I built a occupancy sensor for my home office. The office was a 3mx3m room with no windows, and very bright custom LED lights. The combination of Radar and PIR was the winner.

    The only problem? The thing knew when I was slacking off. It never false-triggered the lights to go off, except if I wasn’t working. Turns out browsing the internet does not give of enough movement for detection :D

    1. That’s the issue to which the newer “Human Presence Detection” variants are targeted, supposedly the better models will trigger just on normal respiration, so in theory they shouldn’t give false negatives unless you are literally dead.

    1. They sense the motion of moving bags of water. If a bag of water enters, it sees the motion of them entering and that the signal is different from baseline. If the bag of water falls asleep, it still has the signal that it’s there.

      This looks like it’s a 24Ghz sensor. Not as good as a 60Ghz, but I figure in 2-3 years this tech will be much better They’re already pretty good at detecting both motion and occupancy. My living room turns the lights on for both motion/occupancy, but after a certain time of night will only trigger for motion because sometimes people sleep on my couch.

      1. The counting must be pretty rudimentary, no? Says it classifies the movement into radial distance bins.
        Is it the 60 GHz where you can detect someone’s breathing and heartbeat? Saw some Texas Instrument demo where they counted people in a parking lot.
        Couldn’t they also have used UWB radar?

  2. Based on the footprint, it’s using a 24Ghz HLK-LD2410 sensor. They’re not as nice as the 60Ghz sensors I use for kitchen/living room occupancy, but it certainly works for not turning off the lights if you play on your phone too long in the bathroom. That board also looks a lot nicer than the various modules attached to perfboard that I’m using, but most of mine have printed shells to cover it up.

      1. The 60Ghz sensors are Aqara FP1 which are ~$50. They’re usb powered and communicate over zigbee. Super easy to setup in HA.

        Apparently the FP2 will be coming out soon and add a few more features/stability. Considering that home radar only really started being a thing 5 years or so ago, Each generation has had massive improvements.

        1. Great info, thanks. I’ve experimented with the inexpensive units with some success, but I’m willing to pay more for reliability (plus the higher freq would be nice for interference reasons).

          1. The one in the kitchen is right next to a PIR, esp32, and Ikea air quality sensor (so the exhaust fan is also automatic) and I haven’t noticed any obvious interference with it.

        2. $50 is too much, by my estimation.

          Let’s assume that electricity is $0.16/kWh.

          Let’s also assume that the occupancy sensor exists to control lighting totaling 12 Watts.

          And that, under manual (direct human) control, these lights burn for 12 hours every average day, and that with the occupancy sensor they burn for 4 hours every average day.

          Let us also assume that the longevity of the lights is not an issue.

          It will take over 7 years for this $50 sensor to pay for itself.

          And maybe that’s a good deal, and maybe it isn’t.

          Will this sensor even be useful after 7 years?

          1. We don’t necessarily need roi. In my case, I care for the fact that I have reliable person detection. It taps into home assistant and sets stuff for me.
            Even the lights, they are DIY led lights so, even lower power than commercial LEDs, but I don’t want them on needlessly when not in the room because I don’t want light bleed in the room nearby.

            If I can have some finer motion control, I could have gestures to enable scenes in home assistant.

            The sensors that detect if you are sleeping are really cool because they can provide interesting data.

            But I agree with you that if you just need to save money that may not be the best solution.

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