Sensor Light

A smart light bar — illuminates dark places on-demand by gently dimming up/down a LED stripe depending on the ambient light level and a detected human presence.

This automatic light is completely self-contained – just needs a suitable 12V power supply.

An advanced (and quite cheap) presence sensor is used here, which works to my satisfaction. However, it should be fine-tuned using the manufacturers app at the final location to get the best out of it.

The circuit and software is designed to save power where possible.
An ESP32-H2 SoC low power processor serves for the logic. It is connected to a VEML7700 ambient light sensor and the mentioned small but effective LD2410 radar based presence sensor.

It does NOT need nor use any Wifi / Zigbee / Matter features of the ESP32-H2 SoC. One may feel free to add some sort of Smart Home connector on his own.

Status: Hardware and Software is feature complete, tested and ready to Roll 'n' Roll.

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Hardware

Wiring diagram

The wiring diagram includes a separate flash adapter (on the left side), which is can be connected to the main unit via a 4-pin connector. It's required to flash the ESP32-H2 once it's soldered. The programming board connects to a computer or any other suitable programming environment via a standard USB-C connector. Please note:

• This programming board is not strictly required in a scenario, when one has its own way of initial flashing the SoC before soldering and don't wish to update the firmware later
• While flashing / monitoring the chip via the flash adapter, we still need power supply through the 12V socket

Parts

LED bar

Designed for 12V and (up to) 35W LED Stripe.

• ESP32-H2-WROOM-03 (the 2MB flash model is sufficient)
• VEML7700 Ambient Light Sensor
• HLK-LD2410 Radar presence sensor (2x)
• BC337-40 TO92 NPN Transistor (2x)
• BC327-40 TO92 PNP Transistor
• IRLB8721PbF N-Channel MOSFET (TO-220)
• Resistor 1kΩ
• Resistor 10kΩ (2x)
• Resistor 4.7kΩ
• Capacitor 0.1µF (2x)
• Capacitor 10µF
• 3.3V LDO voltage regulator LD1117V33 (SOT-223)
• Diode (any, working at 3.3 V and 150mA max.)
• 5m LED Stripe (12V, 3000-3200k, COB, 8mm wide, power: 5-7 W/m)
• 12V DC Connector
• 12V, 5A Power Supply (look for a good one to avoid flickering)
• Wiring Board
• 4 Pin Connector Mini Socket
• Cables
• LED Housing (5m)

USB Flash Adapter

• USB-C Plug Female
• 4 Pin Connector Plug + Cable
• On/Off Switch

Software

Complete program code is included under /code

We are going to use an ESP32-H2 SoC with Rust embedded Toolchain with the [std] lib. Here is an overview of what's needed to build and run the software:

• Rust compiler (see www.rust-lang.org)
• Rust embedded toolchain for ESP32-H2 for projects using std lib
  • Follow the instructions for [std] projects in this book chapter: The Rust on ESP Book - Setting Up a Development Environment
  • Notes:
    • ignore sections for [no_std]
    • When it comes to the step espup install, you should consider using espup install --targets esp32h2 instead, to avoid installing lots of unnecessary dependencies for unused Espressif targets.
• cargo build

After connecting the ESP32-H2 via a flash adapter to a USB computer port:

• cargo run --release (flashes the chip)
• espflash monitor (optional – see ESP32 console output)

Prototype pictures

Terms & Conditions

Feel free to use anything here for learning, building your own version or make a product out of it and sell it.
Have fun!

Pull requests are welcome.

bitmagier, September 2024

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