Introduction

This is a step by step guide on how to build an mmWave presence detection using DFRobot SEN0395, D1 Mini ESP-8266 and ESPHome.

The custom module in the code above is used to implement a room presense sensor and exposes the presense detection sensor and the radar's configuration variables to Home Assistant via the ESPHome integration.

For a more advanced multi-sensor, including temperature, humidity, air quality and air pressure refer to my project here: https://github.com/igiannakas/Presense-Temperature-Humidity-Air-Quality-multi-sensor-DFRobot-SHT35-or-BME680-

This is based on the excellent work done by CRlogic in the HA forums and documented here: https://github.com/hjmcnew/esphome-hs2xx3a-custom-component/tree/release

In this fork of the code, the code is adapted to:

1. Deliver a very compact build as the DFRobot sensor is stacked on top of the D1 Mini
2. Trimmed down the code by CRLogic to improve stability for the low power D1 Mini. The sensor is purely focused on presense and motion detection, which is the core use case.
3. Prettify the exposed sensor names to Home Assistant to reflect the name of the room the sensor is in
4. Contain the full sensor yaml configuration to simplify the setup process

Bill of Materials:

To make this DIY room presense sensor you'll need the below components:

1. D1 Mini
2. DFRobot SEN0395 (from Digi Key, Mouser, Arrow.com, Farnell.com, AliExpress)
3. Mini USB cable and a USB power supply (I use my old phone chargers)
4. Soldering iron
5. 5 cm / 2 inch of wire
6. Optional: 3d printed case (either the one in the folder above or the slightly larger case I've published here if you are using an ESP32 Mini: https://www.printables.com/model/520547-esp32-temperature-and-optional-mmwave-radar-presen)

Wiring instructions:

To get the smallest possible size we stack the sensor on top of the D1 Mini using the pins that come with the D1 mini. The wiring diagram below reflects a stacked configuration: Sensor Pin -> D1 Mini Pin

1. TX -> D1
2. RX -> D2
3. IO1 -> not connected
4. IO2 -> D0 (using the wire)
5. G -> G
6. V -> 5V

For the D1, D2, G and 5V pins we will use header and pin connectors soldered on the D1 mini and the mmWave sensor. The D0 - IO2 connection happens via a wire which is soldered on the D0 pad of the D1 mini and the IO2 pad of the sensor.

Assembly images

Solder the header connectors and the single wire to the D1 Mini as below:

Solder the pins to the outer two sets of pads on the sensor (TX, RX, G, V) and then solder the single wire to IO2

Plug in the sensor to the D1 mini,making sure the V sensor pin is aligned to the 5V header on the D1 mini

As you can see this is a super compact sensor, barely bigger than the D1 mini itself.

Installing ESPHome and the mmWave code

1. Setup your esphome environment. For instructions: https://esphome.io
2. Clone this repository to your build environment. Download the code zip and unpack it in your esphome build directory
3. Open the sensor.yaml file and modify the following variables to match your setup:

device_name: the sensor's device name. This must be in lower case and any words separated with hyphens (-). For example: living-room-occupancy-sensor
device_name_pretty: This is the name of the occupancy binary sensor that will be exposed to home assistant. It can be upper and lower case and can contain spaces. For example: Room Name Occupancy Sensor
ssid: type your 2.4ghz wifi SSID
wifi_password: type in your wifi password

4. Do not modify the uart_tx_pin, uart_rx_pin, gpio_pin values unless you're using a different pinout connection.
5. Deploy the code. I have installed esphome on my mac so I use the following command to deploy the code: esphome run sensor.yaml . If it is a fresh D1 Mini, it doesnt contain the esphome code. For the first flash, you'll need to plug it in to your computer or HA box and flash it. Any subsequent updates will happen over the air.

For a tutorial on how to setup your esphome instance read up here:

1. From the command line & using docker: https://esphome.io/guides/getting_started_command_line.html
2. From home assistant OS: https://esphome.io/guides/getting_started_hassio.html

Setting the sensor up in HomeAssistant and configuring its parameters

The sensor should be autodetected in your homeassistant dashboard. Go to Settings - Devices & Services and add the integration. Then you should be presented with the following device dashboard:

Here you can:

1. See the occupancy sensor value (clear / detected). This is the sensor you will use in your automations.
2. Distance: this variable can be used to set the maximum distance the sensor can see. It defaults to the sensor default value.
3. Latency: this is the sensor cool down period, i.e. how long should no presence be detected before the occupancy sensor is set to "Clear". It defaults to the sensor default value.
4. Led: a toggle switch to turn the sensor LED on or off. On initial setup it defaults to off but the sensor LED is on and blinking. So if you want to turn the sensor LED off, switch it on, wait for 10 seconds then switch it off again. The value should now persist in the sensor's memory
5. mmwave_sensor: This toggle switch turns the motion sensor (radar) on or off. It defaults to on, but is reported as off until the first time presense is detected. Can be usefull if you need to disable motion sensing from an automation or script.
6. Sensitivity: How sensitive the sensor is to movement. The Radar sensor is very sensitive to movement in order to deliver meaningfull presense detection but it can be triggered falsely with the movement of curtains, clothes etc. If you want to reduce sensitivity reduce this number. It defaults to 7, which is a good balance but if you are finding that the sensor reporting as clear when the room is occupied increase this to 9.
7. use_safe_mode: restarts the D1 mini in safe mode
8. Restart: restarts the sensor
9. Factory reset mmWMCU: resets the radar to its factory default settings. (distance, latency, led, sensitivity)

The sensor distance, latency, mmwave_sensor, sensitivity values are read from the radar's presistent memory. They persist reboots but reporting the values to HomeAssistant is delayed. It will take 5-10 minutes after you reboot the D1 Mini for the values to be reported so be patient until they are populated before making any changes.

Every time you change a value you need to wait ~15 - 20 seconds for the value to be written to the DFRobot radar sensor memory and for the radar to restart. While the D1 mini is writing the values to the radar's memory you'll see the LED light turn red. Once it starts blinking or is off (depending on your settings) the values are now written in memory and are persistent through reboots.

Sensor case

I've designed a basic case for the sensor which should provide a snug fit to its components. The STL file is included in the respository above. The case has been tested with the D1 mini and the above sensor and also with a D1 mini and an LD2410 mmwave sensor.

There are two linds in the file - a tight and a loose fitting one. Depending on your 3d Printer tolerance print one of the two lids to allow for friction fit.

Troubleshooting

What I have found is that the sensor is very sensitive to motion (which is what you want in order to get room presense). However, that might lead to false positives, when for example, you have a window open and objects move.

In that situation, your best bet is to experiment with placement, the distance parameter and lastly if everything else fails, the sensitivity parameter. You dont want sensitivity too low, as it wont be able to detect the micro movements that humans do when siting around though!

Also if you are sleeping on the sofa and covered with a blanket the sensor might not detect you - a larger cooldown period (latency) can help here but you're trading off the lights being on for longer when noone is actually present.