PWM Card Assembly Guide

Table of contents

1. PWM Card Assembly Guide
   1. Introduction
   2. Safety Precautions
   3. Assembly-Configuration Options
   4. Assembly and Component Placement
   5. Tools Required
   6. Testing and Verification
      1. Visual Inspection
      2. Connectivity Testing
      3. Card Configuration Settings
      4. Power-Up Tests
      5. Functional Testing
         1. HW Communications Testing
         2. PWM IC Testing
   7. Troubleshooting
   8. Appendences
      1. Specifications
      2. How It Works
      3. Protection
      4. References

Introduction

See the How to Use Assembly Guides for detailed instructions.

The PWM (Pulse Width Modulation) Card, in synergy with the LCC Fusion Node Card, forms the signaling and motor control backbone of the LCC Fusion Project system, controlling signal lamps and motors.

For example, when controlling signals, upon detecting a train within a block, a BOD Card generates an LCC event, signaling the occupancy status. This event is captured by the LCC Node, which, depending on the setup, could trigger various responses such as activating the PWM Card. This activation allows for nuanced control over railroad signals and other trackside functionalities, enhancing the realism and operational efficiency of the model railroad environment.

The PWM Card hardware configuration includes:

• network cable sockets for up to 16 output lines
• selection of the communication bus (BUS or BUS B)
• selection of the communication address (0-7)
• selection of 5V or 12 V for lines 8 and 16 when they are configured for V+
• selection of whether Line 8 & Line 16 are to be used for output or V+ (5 V/12 V)

flowchart LR
can["CAN Network"];
subgraph layout ["Train Layout"];
  direction LR;
  can --> |"LCC Event<br/>(on/off)"| n["Node Card"];
  n -->|"PWM Signal, <br/> Digital Output (high/low)"| c["PWM Card (16x)"];
  
  c --> |"PWM Signal <br/> LED Control (on/off/brightness)"| bb1["LED Breakout Board"];
  bb1 --> led(("LED <br/> (8x)"));
  
  c --> |"PWM Signal, <br/> LED Control (led#, on/off/brightness)"| nbb["NeoPixel Breakout Board"];
  nbb --> neopixel(("NeoPixel <br/>(16x)"));
  
  c --> |"PWM Signal, <br/> (speed/direction)"| bb2["DC Motor Breakout Board"];
  bb2 -->|"Motor Control (speed/direction)"| dcmotor(("DC Motor <br/> (2x)"));
  
  c --> bb3["Servo Motor Breakout Board"];
  bb3 --> |"Servo Control, <br/> (position)"| servo(("Servo Motor <br/> (8x)"));
end
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class c lSalmonStyle;
classDef lightGrayStyle fill:#d3d3d3,stroke:#333,stroke-width:2px,font-size:24px;
class layout lightGrayStyle; 

Safety Precautions

• See Safety Precautions.

## Terminology

• Accessory Bus

• Bus

• Cleaning PCB

• Component

• Current Limiting Resistor

• Decoupling Capacitor

• Edge Card Connector

• ESD Protection Diode

• esp32_s3 - not defined

• Ferrite Bead

• GPIO Expander

• HW Communications Address

• HW Communications Bus

• I2C (Inter-Integrated Circuit)

• I2C Bus

• jumper_caps - not defined

• LCC Configuration Tool

• lcc_event_id - not defined

• LCC Event Monitoring Tool

• LCC Fusion Breakout Boards

• LCC Fusion Cards

• lcc_fusion_io_cards - not defined
• lcc_fusion_node_bus - not defined
• lcc_fusion_node_card - not defined

• LCC Fusion Project

• MCP23017

• Network Cable

• output_cards - not defined
• pwm - not defined

• Stencil

• TVS Diode

For other terms, please refer to the full Terminology Guide.

Assembly-Configuration Options

The PWM Card supports only one assembly configuration with all of the following components installed.

The ESD protection diode D18 is recommended, but not required.

Assembly and Component Placement

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.
• See also: Soldering Tips
• PCB Components - listing of components used for PCB assembly
• PCB Parts - listing of parts used for PCB assembly

Below is a list of the PCB components used for this card (see diagram before reference):

Component Identifier	Count	Type	Value	Package	Purpose	Orientation
C1	1	Capacitor-Ceramic	0.01 uF (100nF), 50 V	1206 X7R	Used to condition/filter the current for the IC (U1)	None
D1 - D17	17	Diode-Schottky	SS310	SMD	Protection against reverse current to ground connections	Cathode end has a white line and positioned towards PCB left edge
D18	1	ESD Diode	PESD1CAN	SOT-23 SMD	I2C data bus electrostatic discharge (ESD) protection	Fits only one way
FB1, FB2	2	Ferrite Bead	BLM31PG121SN1L	1206 SMD	I2C Data Line Noise Suppression Ferrite Bead	None
J1, J2	2	Connector	RJ45 socket (8P8C)	PTH	Network cable (CAT5/6) connection to (1 or 2) breakout boards (e.g. Signal Masts Breakout Board)	Fits only one way
JP1, JP2	2	Male Header	3-Pin	2.54mm PTH	Use for setting lines 8 & 16 to operate as ground either as output lines, or as V+ (5 V or 12 V based on the VOLTAGE selection)	None
JP3	1	Male Header	3-Pin	2.54mm PTH	Used for setting of the output voltage for lines 8 and 16, when the lines are configured for V+	None
JP4, JP5	2	Male Header	3-Pin	2.54mm PTH	Used for COMM BUS selection (I2C hardware bus) for either BUS A or BUS B. These are the ESP32 hardware buses used for serial comms	None
R1-R16	16	Resistor	1KΩ	1206 SMD	Used to limit the current thru the output lines	None
R17 - R19	3	Resistor	10KΩ	1206 SMD	Used to limit the current for the BUS ADDR lines	None
SW1	1	DIP Switch	3-Pin	2.54mm PTH	Used for COMM ADDR selection (I2C address offset, 0-7). This offset is added to the I2C base address of the MCP23017 IC (0x20)	Position so switch so ON is towards PCB top edge
U1	1	IC	PCA9685	TSSOP28 SMD	PWM Expander using I2C serial interface to control 16 PWM pins, each connected to an output line	IC indent (pin 1) is positioned towards PCB left edge
Q1, Q2	2	IC	TBD62083	SOIC-18/SOP-18	Darlington Transistor Array for switching supply voltage to the output lines. Controlled by the PCA9685 IC signals	IC indent (pin 1) is positioned towards PCB bottom edge
SH1 - SH5	5	Jumper Cap	2.54mm	N/A	Used with I2C Bus and Vcc selections. Recommend tall caps for ease of use	None

Tools Required

For a list of recommended tools, refer to List of recommended tools.

Testing and Verification

Visual Inspection

1. Initial Check: Examine the board for any obvious issues like missing components, solder bridges, or components that are misaligned or not fully seated.

2. Solder Join 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.

3. 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.

Card Configuration Settings

1. 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.

2. Configure the PWM Card:

   1. Select the COMM BUS by positioning (2) Jumper Caps on either A or B male header pins (JP1, JP2)

   2. 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.

   3. Select the LINE 16 function to be OUTPUT to verify the connection to an LED works.

      Later change LINE 16 selector to GND along OUTPUT COMMON set to either GND ro V+to test using line 16 for completing the circuit for the LEDs (either as a GND connection or as the V+ connection to the LEDs).

Power-Up Tests

1. Assembly a tested Power Module to the LCC Fusion Node Card.
2. 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 controling signal lamps (LEDs).

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.

1. Insert the PWM Card into a Node Bus Hub along with a LCC Fusion Node Card.

2. Install LCC Fusion Project firmware that includes serial monitor for testing.

3. Verify that the I2C connection between the LCC Fusion Node Card and the PWM Card work.

   See Testing I2C Cards for details on how to test the communications for a I2C enabled card.

PWM IC Testing

After hardware communication has been established, verify the PWM IC is able to drive LED devices using a Signal Masts Breakout Board. Use the Node’s serial monitor to simulate an output request to drive of the PWM Card’s output pins to an LED connected to the Signal Masts Breakout Board as follows:

1. In the serial monitor’s input, enter M for the LCC Node’s serial monitor Main Menu.
2. Select [1] Node Management and [1] Device Testing Management
3. Select [5] Simlulate PWM Device Output
4. From the list of MCP devices, select the device # for the PWM Card being tested
5. Enter the number for the pin to tested.
6. Verify the output device (LED) is turned on
7. Repeat for each of the output lines

Troubleshooting

• See I2C Trouble Shooting.

Appendences

Specifications

Specifications for the card include:

Characteristic	Value
Max output lines	16
Maximum Number of Cards per LCC Fusion Node Cluster	161
Max Current per line (TBD62063 transistor limit)	500 mA
Max Current all lines (Node Bus Hub limit)	1.5A

1. 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 0x40 (PCA9685 IC).

How It Works

This section delves into how the PWM Card operates within the system:

At its core, the PWM Card’s operation is orchestrated through the LCC Fusion Node Card’s firmware, which communicates with the PCA9685 IC— a crucial port expander on the PWM Card. This interaction is facilitated through specific bus and address settings detailed in the CDI I2C section of the card.

Upon receiving instructions to activate (set HIGH) or deactivate (set LOW) a pin, the PCA9685 IC controls a corresponding darlington transistor (TBD62034). This transistor, in turn, manages the switching of an output line on or off.

To tailor the PWM Card’s behavior to specific needs, Jumper Caps are employed to configure the selection pins as outlined below:

Selector Label	Components Indicator	Options	Description
LINE 8	JP1	OUTPUT, V+	Configures line 8 for either: - OUTPUT mode, where it behaves like the other output lines. - V+ mode, serving as a voltage connection to the breakout board for use with lines 1-7. Use V+ mode when external devices or LEDs on these lines need a power source.
LINE 16	JP2	OUTPUT, V+	Configures line 16 for either: - OUTPUT mode, where it behaves like the other output lines. - V+ mode, serving as a voltage connection to the breakout board for use with lines 9-15. Use V+ mode when external devices or LEDs on these lines need a power source.
VOLTAGE	JP3	12 V, 5 V	Selects the voltage level for the V+ option (when V+ is selected on line 8 or line 16). This setting applies only to lines configured in V+ mode and does not affect lines in OUTPUT mode.

The card utilizes current-limiting resistors for each line to manage device output current. The default resistor value is marked for creating about 50% LED brightness, but this can be adjusted by replacing the resistor for each line to suit specific requirements.

Protection

To ensure the reliable operation and longevity of your PWM Card, several protection components have been integrated. These components safeguard the PWM Card from overcurrent, voltage spikes, and electrical noise. Below is a brief overview of each protection element and its role:

Protected Component	Protection Component	Function	Specifications	Location
TBD62083 IC	Decoupling Capacitor 0.1 µF	Filters out high-frequency noise and transient voltage spikes from the power supply, ensuring a stable voltage for the MCP23017.	Value: 0.1 µF	Across Vcc and GND near the MCP23017
I2C Lines from LCC Fusion Node Bus Hub	Ferrite Bead BLM31PG121SN1L	Provides high-frequency noise suppression on the I2C lines.	Impedance: 120 ohms at 100 MHz	In series with the SDA and SCL lines of the I2C bus
I2C Lines from LCC Fusion Node Bus Hub	ESD Protection Diode PESD1CAN	Protects the I2C lines from electrostatic discharge and voltage spikes.	Reverse Stand-off Voltage (Vr): 24 V Clamping Voltage (Vc): 40 V	Across the SDA and SCL lines from the card’s edge connector to GND, near the MCP23017.
Output Lines	SS310 Diodes	Protect against reverse voltage by blocking current flow in the wrong direction.	Reverse Voltage: 100 V Forward Current: 3A	Clamping diode In series with all output lines

References

• I2C Output Mapping (PWM Card)

The PWM Card uses a PCA9685 to generate 8 independent PWM signals. Each line corresponds to one output channel on the PCA9685. Output voltage is either 5V or 12V, depending on configuration.

RJ45 Line	PCA9685 Channel	Direction	Voltage Level	Logic Levels	Purpose	Notes
L1	CH0	Output	5V/12V PWM	HIGH = ON (PWM > 0)	PWM Output 1	Drives LED, motor, or other load
L2	CH1	Output	5V/12V PWM	HIGH = ON (PWM > 0)	PWM Output 2
L3	CH2	Output	5V/12V PWM	HIGH = ON (PWM > 0)	PWM Output 3
L4	CH3	Output	5V/12V PWM	HIGH = ON (PWM > 0)	PWM Output 4
L5	CH4	Output	5V/12V PWM	HIGH = ON (PWM > 0)	PWM Output 5
L6	CH5	Output	5V/12V PWM	HIGH = ON (PWM > 0)	PWM Output 6
L7	CH6	Output	5V/12V PWM	HIGH = ON (PWM > 0)	PWM Output 7
L8	CH7	Output	5V/12V PWM	HIGH = ON (PWM > 0)	PWM Output 8	May share GND depending on config