Mini ESPHome Motion & Light Sensor - D1 Mini

I use a lot of ESPHome based motion and light sensors in my Home Assistant setup. If there is a readily available 5 volt supply, I will use them in place of Zigbee sensors. I just find them more dependable.

The aim of this project was to come up with a 3D printable case design that was as small as practically possible, using the readily available Wemos D1 Mini (clone) ESP8266 board, together with an AM312 motion sensor and a simple LDR based light sensor.

The design I came up with isn't much bigger than an Aqara Zigbee sensor and doesn't look bad either (IMHO).

Design Features

• No-screw clip frame for the D1 Mini. Fits the majority of clone boards that have angled corners at the Wi-Fi antennae end.
• Additional frame to hold a small section of strip-board. Can make the wiring more straigtforward as there is only a single 3.3v and ground pin on the D1 Mini.
• Push in mounting for the AM312 movement sensor.
• Push through mounting for the LDR (dab of superglue gel or some double-sided tape to secure it).
• Two outer case designs. The one pictured and an additional design with a window for a DHT22 temperature/humidity sensor.
  Please note, the DHT22 will be in very close proximity to the D1Mini which will significantly skew the temperature readings.
• Top and bottom panels are secured with M2 cap head hex screws (minimum 5mm long).
• Open backs to the D1Mini and stripboard mounting frame and additional slots for routing hook-up wires.

NOTES

• Try and get D1 Minis without the header pins pre-soldered. They will not fit in this case and would be a pain to remove!
• Most AM312 sensors come with a 3pin DuPont header already soldered to the board - there is no room for this - it will need to be removed.
• You will need some flexible hook-up wire. I like to use multiple colours to indicate what goes where.
• You will need a 10k resistor to act as a voltage divider when used in combination with the LDR.
• To keep the design as compact as possible, the Micro USB is not used to provide power. I simply cut and stripped the end of a USB cable and soldered the power conductors directly on the D1 Mini +5v and GND.

Order of Assembly

It can be a bit of a juggle getting everything connected and assembled. It's also quite difficult to explain so I would suggest doing a dry run based on the following order:

1. Glue the LDR in place (you may need to open the holes slightly).
2. Trim the LDR Leads so they are about 10mm long.
3. Solder flexible hook-up wire to the LDR leads - make it at least twice the height of the case. It's easy to trim!
4. Bend the LDR leads in opposite directions against the inside of the case and put some electrical tape over them (sticking them to the inside of the case).
5. Solder hook-up wires to the AM312 (same length as above).
6. Push the AM312 through the front of the case. It's a tight fit so you may want to temporarily remove the dome (it will just pull off) and push against a hard, flat surface).
7. I used the stripboard to 'expand' the 3.3v and GND connections on the D1 Mini. You don't have to do this - you can just link between the sensors but, I do find mounting the 10k resistor is easier if soldered on the board.
8. If using the 2 frames, place them back to back and run the wiring through the frames, soldering onto the relevant D1 Mini pins.
9. Solder on the 5 volt supply wires.
10. Put a small cable tie around the 5v supply cable (right at the point where it is stripped). Make sure it is tight so it can act as strain relief.
11. Slip the 2 frames into the case slots.
12. Give it a test before attaching the top and bottom panels!

Breadboard Circuit Diagram

Sample ESPHome Configuration

substitutions:
  devicename: replace-this-with-your-device-name
  upper_devicename: Give it a nice name

esphome:
  name: "${devicename}"
  platform: ESP8266
  board: d1_mini 

logger:
api:
ota:
  - platform: esphome

wifi:
  ssid: !secret ssid
  password: !secret wifipass

# Set a static IP or reserve one for each device on your router
#  manual_ip:
#    static_ip: 192.168.0.10
#    gateway: 192.168.0.1
#    subnet: 255.255.255.0

  # Enable fallback hotspot (captive portal) in case wifi connection fails
  ap:
    ssid: "${devicename} Hotspot"
    password: ""

captive_portal:

web_server:
 port: 80

binary_sensor:
  - platform: gpio
    pin: D5
    name: ${upper_devicename} Motion
    id: pir
    device_class: motion
    filters:
     - delayed_on: 300ms 
     - delayed_off: 30s 
# The delayed on filter above can help with false triggers
# Delayed off is the time it takes for the sensor to effectively reset.

sensor:
  - platform: adc
    pin: A0
    name: ${upper_devicename} Lux
    update_interval: '30s'
    unit_of_measurement: lux
    filters:
      - lambda: |-
          return (x / 10000.0) * 2000000.0;                  
# Light measurement with an LDR is never going to be accurate compared with a true lux sensor.
# The lambda filter above gets it within a reasonable and useable ballpark

3D Print Files

STL files for this project are available on Cults3D:
https://cults3d.com/en/3d-model/gadget/mini-motion-and-light-sensor-wemos-d1-mini

Buy Me A Beer

As you can imagine, this design took several hours to perfect.
If you find it useful, please consider a small donation via Paypal:

https://www.paypal.com/paypalme/johnbeardon

Thank you!