During the course of the pandemic I spent a log of time learning about Bluetooth and implemented a novel
Bluetooth people counter for the Raspberry Pi. It won a $20,000 global health competition and I've continued
to develop it further.
I'm going to expand on this topic but here's a few quick pointers:
Mac Address Randomization
Cellphones are designed to be hard to track, they skip mac addresses at random intervals.
BLUEZ
BlueZ is the Bluetooth stack built into most Linux distributions.
SaltStack
Saltstack is a great way to manage a farm of Raspberry Pi or other Linux computers. I can run the same command
on 20 different Raspberry Pis spread across three countries with ease.
iBeacons
deWalt and Milwaukee make great stick on beacons.
Asset Tracking
I now have asset tracking for tools and dogs around our house or barn.
I've been working on home automation for over 15 years and I'm close to achieving my goal which is a house that understands where everyone is at all times, can predict where you are going next and can control lighting, heating and other systems without you having to do or say anything. That's a true "smart home".
My year long Bluetooth project that won the $20,000 HCI and Microsoft competition during lockdown has continued to grow and now reliably tracks how many people are in the house and outside and can locate any device down to room level.
Digital Twin are an online representation of a real world object, a copy of its properties in the digital world and a way to send updated and commands to it. In effect I've been making them for years but now they have a trendy name.
An overview of the many sensors I've experimented with for home automation including my favorite under-floor strain gauge, through all the usual PIR, beam and contact sensors to some more esoteric devices like an 8x8 thermal camera.
One way to reduce the volume of sensor data is to remove redundant points. In a system with timestamped data recorded on an irregular interval we can achieve this by removing co-linear points.
ESP32 provides a great platform for sensors around the house but by the time you've added a USB power brick, cable and enclosure it's quite messy. I wanted a device that I could just plug in with no exposed wires and no mounting needed so I designed one in OpenSCAD.
Bluetooth sensing for home automation is a great proxy for people counting as it can detect and locate each cellphone in the house. iBeacons attached to tools, cars and pets can provide a 'find my anything' feature too.
Microwave doppler sensors can be found in some alarm sensors but there are also available very cheaply as a separate component. They offer exceptional range but suffer from false triggers requiring a probailistic approach to people sensing.
Optical-beam sensors are reliable and can cover a long-distance such as across a garage or aisle-way. When they include multiple-beams they have good false-trigger rejection.
Another super useful function for handling sensor data and converting to probabilities is the logistic function 1/(1+e^-x). Using this you can easily map values onto a 0.0-1.0 probability range.
In a home automation system we often want to convert a measurement into a probability. The ATAN curve is one of my favorite curves for this as it's easy to map overything onto a 0.0-1.0 range.
An if-this-then-that style rules machine is insufficient for lighting control. This state machine accomplishes 90% of the correct behavior for a light that is controlled automatically and manually in a home automation system.
