The Blog of Ian Mercer.

Bluetooth

Bluetooth

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.

Related Stories

Home Automation

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".

Ian Mercer
Ian Mercer

Bluetooth Tracking Project

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.

Ian Mercer
Ian Mercer

Digital Twins are never identical

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.

Ian Mercer
Ian Mercer

Home Automation Sensors

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.

Ian Mercer
Ian Mercer

3d Printed ESP32 Brick

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.

Ian Mercer
Ian Mercer

Bluetooth Sensing for Home Automation

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.

Ian Mercer
Ian Mercer

Microwave Doppler Sensors (RCWL-0516)

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.

Ian Mercer
Ian Mercer

Optical-beam sensors

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.

Ian Mercer
Ian Mercer

PIR Sensors for Home Automation

PIR sensors are cheap and easy to use but they suffer from slow response times and low repeat rates.

Ian Mercer
Ian Mercer

Strain-gauges

Strain-gauges are my top-rated sensor for home automation because they are invisible, reliable and can be tuned to detect people and ignore pets.

Ian Mercer
Ian Mercer

Logistic function - convert values to probabilities

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.

Ian Mercer
Ian Mercer

ATAN curve for probabilities

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.

Ian Mercer
Ian Mercer

Probabilistic Home Automation

A probabilistic approach to home automation models the probability that each room is occupied and how many people are in that room.

Ian Mercer
Ian Mercer

Multiple hypothesis tracking

A statistical approach to understanding which rooms are occupied in a smart house

Ian Mercer
Ian Mercer

A state machine for lighting control

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.

Ian Mercer
Ian Mercer

iBeacons for Home Automation

My investigations into using iBeacons for home automation

Ian Mercer
Ian Mercer

iBeacon meetup in Seattle - January 2015

My notes on the iBeacon meetup in Seattle held in January 2015

Ian Mercer
Ian Mercer

The Internet of Hubs (and things)

Maybe it should be called the Internet of Hubs instead

Ian Mercer
Ian Mercer

World's Smartest House

Over 15 years of experimentation with home automation

Ian Mercer
Ian Mercer

Pressure Sensors for Home Automation

Pressure sensors can detect HVAC system operation and could potentially detect clogged filters.

Ian Mercer
Ian Mercer