Dakboard HDMI Dimmer - Hardware

A Raspberry Pi HAT that carries a BH1750 ambient-light sensor and a PIR motion sensor for automatic HDMI display dimming.

Designed for the Raspberry Pi Zero 2 W, but it mounts on any Raspberry Pi with the standard 40-pin header. Pairs with Dakboard-HDMI-dimmer-FW, which reads these sensors and adjusts display brightness.

What's on the board

• 40-pin GPIO header (J1) - mounts the board as a HAT and breaks out power, I²C, and the PIR line
• BH1750 light sensor header (J2) - 5-pin module (VCC / GND / SCL / SDA / ADDR) on I²C bus 1, address 0x23, with 4K7 pull-ups
• PIR motion sensor header (J3) - 3-pin module (VCC / OUT / GND) with the output on GPIO24 (BCM), physical pin 18
• Decoupling and signal-conditioning passives, plus four mounting holes

The BH1750 runs at 3.3 V on the Pi's primary I²C bus; the PIR is powered from 5 V and its output is fed to a GPIO. All dimming logic lives in the firmware - this board just carries the sensors.

Pin usage

Signal	Raspberry Pi pin	Notes
I²C SDA	GPIO2 / pin 3	BH1750 (bus 1, addr 0x23)
I²C SCL	GPIO3 / pin 5	BH1750
PIR out	GPIO24 / pin 18	Motion detection
3V3	pin 1	BH1750 supply
5V	pin 2 / pin 4	PIR supply
GND	pins 6, 9, 14, …	Common ground

Board specs

• Size: 30 × 65 mm
• 4× mounting holes
• 2-layer, JLCPCB-ready gerbers included

Repository layout

Dakboard HDMI dimmer KiCAD/
└─ Dakboard HDMI dimmer v1/
   ├─ Dakboard HDMI dimmer v1.kicad_pro   # KiCAD project
   ├─ Dakboard HDMI dimmer v1.kicad_sch   # schematic
   ├─ Dakboard HDMI dimmer v1.kicad_pcb   # PCB layout
   └─ gerber_to_order/                    # zipped gerbers for JLCPCB

Manufacturing

The gerber archive in gerber_to_order/ is ready to upload to JLCPCB (or any fabricator) as-is. To modify the design, open the project in KiCAD 7 or newer.

Below is an example of full HW installation with custom cabling