ESP-IDF Death Watch for the ESP32

This IoT project is lovingly called Death Watch because it serves a very simple purpose: it reports in-house activities so that some action can be taken should occupants seize to seem alive. It is designed to be run on the Espressif ESP32 and compiled using the ESP-IDF framework.

Rationale

Although there may be many reasons do this, in my case this IoT project solves the What if I die (or am otherwise detained), in or out of the house, and the pet(s) are left unattended and nobody knows? dilemma. It could equally well serve to monitor senile/disabled/elderly individuals (although there are probably better tools).

There are obviously many ways to solve this problem, but I wanted something that's more reliable than my phone. In fact, I wanted it to rely on as little hardware as possible, so I didn't involve any of my own servers or privately hosted code, relying instead only on WiFi and Google.

Setup

The ESP-32 board is connected to:

• A motion sensor (ie HC-SR501) - detects human motion, placed where pets will not trip it (garage in my case)
• An ultrasonic rangefinder (ie HC-SR04-P) - detects garage door position (both for fun and to serve its purpose). Intended to be mounted on the ceiling pointed down, this can then identify 3 states:
  1. Door open (short distance to door)
  2. Car present (medium distance to car)
  3. Door closed (long distance to floor)
• A temperature sensor (DS18B20) - measures garage temperature just for fun.

It then does the following:

• Monitors above sensors and collects data.
• Reports said data periodically via an HTTPS (SSL) POST request (eg: to Google Forms)
• Also provides a webserver that allows said data to be retrieved via HTTP, if you want (JSON).

What you do with the data is up to you, but with Google Forms, the idea is to:

• Have time-series data in a spreadsheet (for example, number of motion events for each hour)
• Run a scheduled Google Script that will send email (for example) when no motion has been detected for X hours.
  • The script could first email you as a warning, and after a further wait - send email to your designated first responders.
  • The script could have a whitelist spreadsheet (eg vacation days when no alarming is needed)
  • The script also sends reminders if the garage door is left open.
• Whatever else.

The above is fully implemented in google docs. In fact, there is almost more logic in the spreadsheet and its associated script than there is in this repository. To access, make a copy (in Google Drive) of this spreadsheet and you should have your own copy of the form and script associated with it. You'll want to set up triggers (in the Script Editor) and thresholds (on the Calculations sheet). Screenshots from the doc:

Circuit

The wiring is trivial, sensors are connected to power, ground and GPIO pins. Some details:

• HC-SR04-P rangefinder is happy with 3.3V input and outputs 3.3V signal (I think), so it connects directly to GPIO. I first used a 5V US-100 rangefinder but it was very unstable (the diagram shows the old wiring). The HC-SR04-P is like an HC-SR04 but works well at low voltage.
• HC-SR501 motion detector takes 5V (taken from 5V pin) but outputs 3.3v, so it's just connected directly to GPIO.
• DS18B20 temperature sensor connects directly to 3.3v power/ground pins and to GPIO for signal, except that a >=3K resistor is used to pull-up (connects signal wire to 3.3v)

All of the above are standard wiring connections and can be found on the interwebs.
ADC1 pins are used for all of the above since WiFi is used (see defaults in menuconfig).

Credits

Various components were adapted from:

• https://github.com/feelfreelinux/ds18b20
• https://github.com/cmmakerclub/esp32-webserver
• https://github.com/Ebiroll/esp32_ultra
• ESP32-IDF Examples

Prerequisites

This application is meant to be used with Espressif IoT Development Framework_ (ESP-IDF) which should be properly installed.

Please check ESP-IDF docs for getting started instructions.

run "make menuconfig" (a large number of configuration options are found in the DeathWatch menu item):

Additional Possibilities:

• Motion detected LED (either controlled by GPIO or directly form the motion sensor pin, depending on power requirements).
• Car position indicator (far enough into garage), probably with a second ultrasonic module. This would have to be measuring very frequently to be useful and will need a bright light of some kind to indicate position.
• Configuration via the built-in webserver (flash storage for settings).
• Control of garage door via webserver (relay to button). Possibly even automatically close the door if left open.