The Sensor Card is a flexible digital input card designed to support a wide variety of powered sensors that provide a logic-level output signal. It supplies power (selectable 3.3 V or 5 V), ground, and a signal return for up to six external sensors via a companion breakout board with standardized 3-pin (V/G/S) headers.
LCC Fusion uses the Digital Sensor Card to connect active sensors such as HTTM capacitive touch buttons, IR beam-break modules, Hall effect sensors, reed switches, and more. Each input line is monitored by the Node Card, which can be configured in firmware to generate LCC Events based on the digital signal state. These events can trigger layout automation, control signals, or initiate behavior in other LCC nodes.
The Sensor Card complements the Button Card (used for passive pushbuttons) and the I/O Card (used for more general digital control). Its modular design, paired with the Sensor Breakout Board, makes it ideal for plug-and-play input integration from a wide variety of logic-based sensor modules.
This section combines both the component specifications and the assembly instructions to ensure a smooth assembly process. Below is a comprehensive list of components, their placement on the PCB, and orientation details to assist you during assembly.
High-Level Steps for Assembly:
PCB for the card can be ordered from any PCB fabricator using these Gerber Files.
Clean PCB with alcohol to remove residue. See Cleaning_PCB for details.
Select the COMM BUS by positioning (2) Jumper Caps on either A or B male header pins (JP1, JP2)
Select the COMM ADDRESS switch (SW1) by sliding each of the 3 switches to either the ON or OFF position. Setting a switch to ON increments the address by 1, 2, or 4 for an address range of 0 to 7. Up to 8 devices can then be configured for A and 8 for B.
The following test and verifications of the card should be performed after a through inspection of the card’s soldering. Check all of the PTH component pins and SMD pads. Make sure there are no solder bridges between pins and pads.
Visual Inspection
Initial Check: Examine the board for any obvious issues like missing components, solder bridges, or components that are misaligned or not fully seated.
Solder Joint Inspection: Use a magnifying glass or a microscope to inspect solder joints. Look for cold solder joints, insufficient or excessive solder, or any shorts between pads.
Component Orientation: the IC’s are correctly oriented according to the PCB silkscreen or schematic.
Connectivity Testing
Continuity Check: Use a multimeter in continuity mode to check for shorts between power rails and ground, and to ensure there are no open circuits in critical connections.
Power-Up Tests
Assembly a tested Power Module to the LCC Fusion Node Card.
Apply Power to the Power Module and verify the following:
Check for Hot Components: Feel for components that are overheating, which could indicate a problem like a short circuit or incorrect component.
Functional Testing
Functional testing of the card can be performed after completing the power-up testing. Testing consists of testing network communiations, followed by the sensing of current in a layout track block.
HW Communications Testing
Communications testing verifies the LCC Node can communicate with the BOD Card’s I2C IC via the Node Bus Hub connections. This is performed using the LCC Fusion Node Card’s testing firmware and a serial monitor.
Insert the BOD Card into a Node Bus Hub along with a LCC Fusion Node Card.
Install LCC Fusion Project firmware that includes serial monitor for testing.
Verify that the I2C connection between the LCC Fusion Node Card and the BOD Card work.
See Testing I2C Cards for details on how to test the communications for a I2C enabled card.
MCP IC Testing
After hardware communication has been established, to verify the MCP IC, use the Node’s serial monitor to simulate an input from each of card’s input pins as follows:
In the serial monitor’s input, enter M for the LCC Node’s serial monitor Main Menu.
Select [1] Node Management and [1] Device Testing Management
Select [5] Simlulate MCP Device Input
From the list of MCP devices, select the device # for the BOD Card being tested
Enter the number for the pin to tested.
Using the JMRI Event Monitor, verify the correct Event ID was issued.
Track Block Testing
After validating the LCC Fusion Node Card can communicate (find) the BOD Card, test each of the BOD Card block connections.
Track block detection verification is performed using a Block Breakout Board connected to a track block.
Connect a network cable (CAT5/6) to one of the BOD Card’s RJ45 connector.
Connect the other end of the network cable to (1) Block Breakout Board.
Connect one of the Test Track rails directly to the Track Bus V+ connection.
Connect the other Test Track rails to one of the Block Breakout Board block connections (BLK1 - BLK4)
Connect the Test Track Bus GND to the Block Breakout Board TRACK BUS GND connection
Configure each of the card’s device lines using an LCC CDI Configuration Tool.
Open an LCC Event Monitoring tool (e.g. JMRI Event Monitoring tool).
Test each of the Breakout Board device connections using a locomotive (one at a time)
Maximum Number of Cards per LCC Fusion Node Cluster
161
The LCC Fusion Node Cluster can support up to 16 cards, distributed across two I2C hardware buses, with a maximum of 8 cards per bus.
Note: total includes all cards using the I2C address range of 0x20 (MCP23017 IC).
How It Works
The Digital Sensor Card works by providing power (3.3 V or 5 V) and ground to external digital sensors, while monitoring the logic-level signal line (S) returned from each sensor through a 3-pin (V/G/S) connector on the Sensor Breakout Board.
Each signal line is routed to a I2C GPIO expander (MCP23017) and cabled to the Node Card, where it is configured in firmware as a digital input. The Node Card monitors the voltage state of each line and triggers LCC Events based on rising or falling signal transitions. This enables real-time layout automation responses to environmental or user input.
Sensors connected to the Digital Sensor Card typically drive their output line either HIGH (active) or LOW (active), depending on type. The Sensor Card supports both configurations by allowing firmware-based options for:
Pull-up or no pull-up resistor
Active-high or active-low event logic
Examples include:
HTTM capacitive touch buttons, which drive the line HIGH when touched.
IR beam-break sensors, which pull the line LOW when an object interrupts the beam.
Hall effect switches or reed switches, which signal LOW when a magnetic field is detected.
This modular sensing system simplifies layout wiring and allows users to plug in a variety of sensors without reconfiguring core logic — all using a consistent 3-wire interface and a single breakout cable per Sensor Card.
Protection
To ensure the reliable operation and longevity of the Sensor Card, several protection components have been integrated. These components safeguard the Sensor Card from overcurrent, voltage spikes, and electrical noise. Below is a brief overview of each protection element and its role:
The Sensor Card receives digital sensor signals from 3-wire active sensor modules. These typically output 5 V logic levels. The card supplies 5 V and GND via RJ45 and reads logic states from L3–L8 using the MCP23017.