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Creative & Custom LED Displays Bespoke Hub Board for
P0.78 COB Medical Device
A medical device developer creating vision testing equipment needed a single standalone P0.78 COB LED module to function as a calibrated stimulus display. But a standard LED module cannot operate independently — it requires a purpose-built Hub Board to bridge the receiving card, power supply, and diode array. With the standard Hub Board designed for 4-8 modules and physically too large, DOIT VISION engineered a bespoke miniaturized Hub Board with ultra-low-profile FPC connectors, custom NovaStar configuration files to force recognition of the unusual standalone hardware, and a precision dual-voltage Common Cathode power circuit. The entire 7-day sprint covered concept through CAD, custom PCB printing, FPC connector assembly, and successful first light-up test.
At a Glance
Why a Standalone Module Won't Light Up
A standard LED module needs a Hub Board to function. The Hub Board is the bridge between the receiving card, power supply, and the LED diode array — it distributes data signals, manages power routing, and provides the physical connectors for data and power input.
Standard Hub Boards are designed for 4-8 LED modules, with corresponding physical dimensions that make them far too large for a medical device enclosure. The client needed to drive a single module — requiring a purpose-built, miniaturized Hub Board physically matched to the 150x150mm module footprint.
Ultra-Low-Profile FPC Design
Standard 120/100-pin connectors were too bulky for the medical device's spatial constraints. For a device that sits millimeters from the patient's face, every fraction of a millimeter in connector height matters.
We sourced ultra-low-profile FPC (Flexible Printed Circuit) connectors — flat ribbon-style interconnects that fold into the enclosure with a profile measured in fractions of a millimeter. These are typically used in smartphone and tablet manufacturing where every micron of internal height is contested.
Beyond physical fit, the FPC connectors had to maintain signal integrity at P0.78 pixel pitch. At sub-1mm pitch, the data rate required to drive the pixel array creates electromagnetic interference (EMI) and electromagnetic compatibility (EMC) challenges that don't exist at coarser pitches. Signal trace length, impedance matching, and ground plane continuity on the custom PCB were all designed to suppress crosstalk and maintain clean data channels.
Dual-Voltage Common Cathode Circuit
The COB module uses Common Cathode architecture, where red, green, and blue LED channels require different forward voltages. Red needs ~2.8V while green and blue need ~3.8V — driving all three at the same voltage wastes power and generates excess heat.
The custom Hub Board included a precision dual-voltage power circuit that splits the single power supply input into two independently regulated outputs: 2.8V for the red channel and 3.8V for the green and blue channels. This Common Cathode design reduces power consumption by 20-25% compared to Common Anode designs that drive all channels at the same voltage.
The client's ocular testing equipment presents calibrated visual stimuli to the patient while measuring pupil response and eye movement. If the LED module generates thermal hotspots — even localized hotspots of a few degrees Celsius — the resulting air convection currents near the patient's face can trigger blink reflexes and skew test results. The Hub Board's power circuit and PCB layout were engineered to distribute heat uniformly across the board surface with no measurable hotspots.
NovaStar .rcfgx Configuration
The NovaStar receiving card expects to drive a standard cabinet configuration — typically 4-8 modules in a defined layout. Connecting it to a single miniaturized module with an unconventional connector arrangement would normally result in the receiving card failing to recognize the hardware or driving the pixels in the wrong order.
DOIT VISION wrote a custom .rcfgx configuration file — NovaStar's hardware descriptor format — that explicitly tells the receiving card how many pixels exist, their electrical mapping to channels, and the signal timing for this specific non-standard configuration. The file was loaded via NovaLCT (NovaStar's LED Configuration Tool) and forced the receiving card to recognize the unusual standalone hardware.
Engineering Specs
7-Day Hub Board Sprint
Constraint Lock
Mapped the medical enclosure: single P0.78 COB 150×150mm module, ultra-low-profile FPC, dual-voltage Common Cathode, EMI/EMC budget, and NovaStar receiving-card interface.
PCB Layout
Miniaturized Hub Board for one module instead of the standard 4–8 module board. Routed 2.8V / 3.8V rails, FPC landing, and thermal copper pours to eliminate hotspots.
Fabricate & Configure
Board fab, connector seating, and custom .rcfgx authoring so NovaLCT recognizes the non-standard single-module geometry on first flash.
First-Light Test
Thermal camera verification (zero hotspots), stimulus uniformity check, and handoff of the Hub Board + config file for the vision-testing device.
Need custom PCB engineering?
Hub Boards, interface boards, custom controllers — we design and fabricate bespoke PCBs from concept to first-light test. Agile sprints from 7 days.
Frequently Asked Questions
Can DOIT VISION design custom interface boards for LED modules?
What is a Hub Board and why does a single LED module need one?
How do Common Cathode dual-voltage circuits save power?
How do you get NovaStar cards to recognize non-standard configurations?
What is the minimum turnaround for custom PCB engineering?
Can you integrate LED modules into medical or scientific equipment?
Do you provide EMI/EMC support for medical device LED integration?
Can the custom Hub Board work with controllers other than NovaStar?
Products & Resources
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