Mixed-Signal · Power Electronics
Electronically Adjustable Neutral Density (ND) Camera Filter
Overview
Engineered a handheld electronic controller capable of precisely adjusting the opacity of a liquid crystal neutral density (ND) filter using a programmable AC drive signal. The project involved three PCB design iterations, custom embedded firmware development, analog power electronics, and hardware optimization to improve performance, reliability, manufacturability, and overall user experience.
The engineering challenge
Traditional variable ND filters rely on manual mechanical adjustment and provide limited electronic control. The objective was to develop a compact battery-powered controller capable of generating stable programmable AC drive voltages for a liquid crystal ND filter while providing preset density levels, manual adjustment, and an intuitive OLED user interface.
Confidential Prototype
Adjustable ND Filter Controller — proprietary prototype; imagery withheld at the client's request.
- Microcontroller
- PIC16F15385
- Power System
- Single-cell Li-Ion battery · MCP73871 battery charger · TPS63070 buck-boost converter
- Display
- SSD1306 OLED
- Analog Circuitry
- MCP4821 DAC · DRV8212 H-bridge
What I owned
- Engineered the complete electronic hardware from schematic capture through PCB layout and routing
- Designed and validated three PCB revisions to improve functionality and manufacturability
- Selected and sourced electronic components based on electrical performance and availability
- Coordinated PCB fabrication, assembly, and prototype validation
- Developed embedded firmware in C for system control and user interaction
- Designed the OLED graphical user interface
- Integrated the DAC, buck-boost converter, H-bridge, battery charging, and battery management circuitry
- Performed hardware bring-up, debugging, and electrical validation using laboratory test equipment
- Optimized hardware and firmware through multiple design iterations
System architecture
Full technical specification
- Microcontroller
- PIC16F15385
- Power System
- Single-cell Li-Ion batteryMCP73871 battery chargerTPS63070 buck-boost converter
- Display
- SSD1306 OLED
- Analog Circuitry
- MCP4821 DACDRV8212 H-bridge
- Firmware
- Embedded C
- Development Software
- Fusion 360 ElectronicsDipTraceMPLAB X IDEXC8 CompilerLTspice
- Test Equipment
- OscilloscopeBench power supplyDigital multimeterHot-plate reflow station
Development process
- 01Requirements Definition
- 02System Architecture
- 03Circuit Design
- 04PCB Layout & Routing
- 05Component Selection
- 06PCB Fabrication
- 07Prototype Assembly
- 08Firmware Development
- 09Hardware Bring-up
- 10Validation & Testing
- 11Design Iteration
- 12Final Prototype
Engineering challenges
- Designing a stable AC drive waveform for the liquid crystal filter
- Optimizing buck-boost converter performance and voltage regulation
- Developing responsive embedded firmware while maintaining stable output characteristics
- Creating a clean and intuitive OLED user interface
- Implementing accurate battery monitoring and power management
- Improving PCB manufacturability through multiple design revisions
- Debugging hardware communication and power sequencing during prototype bring-up
Skills demonstrated
Outcome
Successfully developed a portable battery-powered ND filter controller capable of generating programmable AC drive voltages with multiple preset ND levels, manual adjustment, an OLED interface, and reliable hardware performance across multiple hardware revisions.