Power switch

Modular I2C GPIO Expander / Power Switch Board (Qwiic-Compatible)

A compact, Qwiic-compatible power switch module built around an I2C GPIO expander, designed for easy integration into modular sensor/electronics setups without extra wiring or a microcontroller doing the switching directly.

Overview

This board lets a host microcontroller switch power to a downstream load over I2C, using a GPIO expander instead of dedicated GPIO pins. It's designed to snap into the Qwiic ecosystem, so it can be daisy-chained with other Qwiic boards with no soldering.

Key Features

• I2C-controlled power switching using the PCA9536 GPIO expander
• PCA9306 I2C level shifter for safe voltage-level translation between 3.3V and 5V I2C buses
• Impedance-controlled I2C routing to keep signal integrity clean on the bus
• MOSFET switching circuitry for the actual load power path
• Status LED indicators showing real-time switch state at a glance
• Qwiic-compatible connectors for plug-and-play integration with other boards

Design Details

• Schematic capture and PCB layout done fully in KiCad
• Routed with attention to I2C trace impedance to avoid signal integrity issues on the bus
• Component placement optimized for a compact footprint
• Manufacturing-ready output: complete BOM, Gerber files, and drill files generated for fabrication

Copper Layers

Assembly Layers

Schematic

Full schematic PDF: Qwiic_Power_Switch_Schematic_v10.pdf

Tools Used

• KiCad (schematic capture + PCB layout)

Files in This Repo

• power switch.kicad_sch / power switch.kicad_pcb / power switch.kicad_pro — full KiCad project
• Qwiic_Power_Switch_Schematic_v10 (1).pdf — full schematic
• 3D front layer.png, 3D back layer.png, 3D side view.png — 3D renders
• front cu layer.png, back cu layer.png, all cu layers.png — copper layer views
• front assemble layer.png, back assemble layer.png — assembly drawings
• schematic.png — schematic preview image
• power switch proj 3 main bom.xlsx — bill of materials with supplier part numbers

What I'd Improve Next

• Add reverse-polarity protection on the input
• Explore a smaller PCA9536 package option to shrink the footprint further

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Part of a PCB design training program (SUREPROED). Designed and routed independently as part of the coursework.