Useful Sensor: Motion Last Seen & Meta Motion Sensor

You know what’s great about motion sensors? They are very, very cheap to build yourself. All it takes is an esp8266 module like the Wemos D1 Mini, some PIR sensors, and the ESP Easy firmware and you can have a bunch up and running in a few minutes. I haven’t DIYed a battery powered one yet, but there are plenty of great Z-Wave ones available.

Once you have a couple of motion sensors in your smart home, you can have Home Assistant track the last place it saw motion. This is a useful bit of info – useful as a condition for your automations, or as an input for a bayesian binary sensor. See below for YAML to create a meta-motion sensor with a history.

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Favorite ESP8266 Internet of Things Projects

So many good uses for these chips, here are a few I’ve made and some I still intend to.

  1. ESP Easy – by far the easiest way to connect a bunch of cheap sensors to an esp8266. I have about 6 of these doing various things.
  2. Bed Occupancy Sensor – FSR sensor for pressure and a simple automation to determine bed occupancy
  3. WiFi Candle Using multiple WS2812 addressable LEDs to create a simple lamp that flickers like a candle.
  4. Notification Flag – Raise a flag based on a simple condition. Would be nice to combine in tandem with…
  5. Mailbox Sensor – Notify when mailbox is opened.
  6. DIY Milight Hub – I’ve been using this and it works great. Control as many cheap Chinese RGB bulbs as you want.
  7. Simple Water Alarm – If water shorts the wires, it wakes a sleeping esp8266 and sounds the alarm
  8. Door/Window Monitor – Along the same lines, a simple magnetic switch monitors the status of a window or door.
  9. Smart Power Strip – Retrofitting a power strip with 2 banks of controllable outlets, using 3D printed parts.
  10. Weather Station Display – Another super cool 3D printed project that plugs in and displays info on a small screen.

My favorite form factor of the esp8266 is the Wemos D1 Mini. Tiny, all the inputs you need, and there are many premade ‘shields’ for it so you can stack components.