The Blog of Ian Mercer.

Gas sensors

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I currently have a VOC sensor in the garage, it provides some 'interesting' data but nothing useful yet.

Gas readings

I recently acquired a CO2 sensor and plan to add that to the system.

A particulate sensor would be a good addition too for the air handling system.

Related Stories

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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
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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
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Collinearity test for sensor data compression

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.

Ian Mercer
Ian Mercer
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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
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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
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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
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Humidity Sensors (DHT11, DHT22, AM2320)

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

Ian Mercer
Ian Mercer
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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
Cover Image for Microwave Doppler Sensors (RCWL-0516)

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
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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
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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
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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
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Temperature sensors for home automation

Temperature sensors I've experimented with for home automation.

Ian Mercer
Ian Mercer
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Event blocks

Home automation systems need to respond to events in the real world. Sometimes it's an analog value, sometimes it's binary, rarely is it clean and not susceptible to problems. Let's discuss some of the ways to convert these inputs into actions.

Ian Mercer
Ian Mercer
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The Grideye 8x8 camera sensor

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

Ian Mercer
Ian Mercer
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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
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Pressure Sensors for Home Automation

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

Ian Mercer
Ian Mercer