The Blog of 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. Typically they run on a 12v power supply and connect into an alarm panel.

Initially I had a single-beam optical sensor across our barn aisle but the IR sender seemed to atrract moths at night and they were capable of triggering the beam. A dual-beam sensor (separated about 20cm apart vertically) provides a much more reliable sensor and the only false alarm I get now is from a large crow that sometimes flies through the barn.

They are suitable for indoor, exposed or outdoor applications but are too ugly for most indoor applications.

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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

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

Filtering techniques

Filtering raw data is essential for a reliable home automation system. Here are some of the many ways you can filter sensor data.

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

Gas sensors

Gas sensors come in many different flavors including CO2, VOC and particulate sensors.

Ian Mercer
Ian Mercer

Humidity Sensors (DHT11, DHT22, AM2320)

Humidity sensors are great for controlling extractor fans in bathrooms and other damp spaces.

Ian Mercer
Ian Mercer

Light sensors for Home Automation

Having at least one light sensor is critical for any home automation system that controls lightng. Lights need to be turned on when it's dark not at specific times of day, especially here in Seattle when it can be dark and cloudy at any time of day.

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

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

Temperature sensors for home automation

Temperature sensors I've experimented with for home automation.

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

Bluetooth

One of my inventions recently won a $20k global competition for applications that could help in a pandemic. It uses Bluetooth to count people.

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

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

The Grideye 8x8 camera sensor

Experiments with an 8x8 IR camera for privacy-preserving people detection using cameras.

Ian Mercer
Ian Mercer

CCTV Cameras as Home Automation Sensors

CCTV cameras are an option for detecting people but within the home there are privacy concerns that need to be addressed.

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