John at 20:32, 11 October 2025

2025-10-11T20:32:49Z

← Older revision		Revision as of 20:32, 11 October 2025
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	{{PCB		{{PCB
	\| name = BRS Differential Drive Robot Control Board		\| name = BRS Differential Drive Robot Control Board
	\| image = ~~PCB_schematic~~.png		\| image = BRS_DDRCB.png
	\| purpose = Integrated motor control and sensor interface for differential drive robots		\| purpose = Integrated motor control and sensor interface for differential drive robots
	\| type = Through-Hole (THT) / Surface-Mount (SMT variant planned)		\| type = Through-Hole (THT) / Surface-Mount (SMT variant planned)

John: Claude edited based on my notes, prompt, and SimpleBot code repository

2025-10-11T16:21:17Z

Claude edited based on my notes, prompt, and SimpleBot code repository

New page

{{PCB
| name = BRS Differential Drive Robot Control Board
| image = PCB_schematic.png
| purpose = Integrated motor control and sensor interface for differential drive robots
| type = Through-Hole (THT) / Surface-Mount (SMT variant planned)
| microcontroller = [[Raspberry Pi Pico]] or compatible 40-pin boards
| components = {{TB6612FNG}}, {{MP1584}}, {{LM393}}, nRF24L01 header, MPU6050 header, sensor expansion
| layers = 2-layer PCB
| cost = $5-10 for 5 PCBs (JLCPCB) + ~$10-15 components
| gerbers = [https://github.com/Bespoke-Robot-Society/simplebot/blob/master/diffdrive_robot_microcontroller_board--tht_Gerber.zip GitHub Repository]
| repository = [https://github.com/Bespoke-Robot-Society/simplebot GitHub - SimpleBot]
}}

The '''BRS Differential Drive Robot Control Board''' is a custom PCB designed for [[SimpleBot]] and other small differential drive robots. It integrates all electronics needed for motor control, power regulation, optical odometry, and sensor expansion onto a single compact board.

== Overview ==

This PCB was designed with BRS's core mission in mind: '''lower the barrier to entry''' for robotics. The through-hole version uses only THT (through-hole technology) components, making it ideal for:

* Educational environments (schools, workshops)
* Beginners learning to solder
* Rapid prototyping without specialized equipment
* Easy component replacement and repair

A surface-mount variant is planned for more compact builds and higher-volume production.

== Key Features ==

=== Integrated Components ===

* '''[[Raspberry Pi Pico]] Socket''' - 40-pin header for any Pico-compatible board
* '''Motor Driver''' - [[TB6612FNG]] module socket or external H-bridge header
* '''Power Regulation''' - [[MP1584]] buck converter (6V → 3.3V)
* '''Optical Encoders''' - [[LM393]]-based comparator circuit for wheel encoders
* '''Expansion Headers''':
** nRF24L01 2.4 GHz radio (SPI)
** MPU6050 IMU (I²C)
** 4× sensor headers (3.3V + GND + GPIO)
** Analog expansion (3× ADC pins)
** Digital expansion (GPIOs)

=== Design Philosophy ===

* '''Through-Hole First''' - Easy to solder for beginners
* '''Modular''' - Use standard breakout modules where possible
* '''Expandable''' - Room for additional sensors and features
* '''Repairable''' - Socketed components can be replaced
* '''Open Source''' - Full schematics and KiCad files available

== Schematic ==

The PCB is organized into functional sections:

=== Power Section ===

[[File:PCB_power.png|thumb|300px|Power regulation section]]

The power section converts 6V from 4× AA batteries to regulated 3.3V:

* '''Input''': 4.5V – 6.5V from battery pack (via power switch)
* '''Buck Converter''': [[MP1584]] module provides 3.3V at up to 3A
* '''Important''': Buck converter must be pre-tuned to 3.3V BEFORE soldering to PCB

The power switch should be wired to disconnect batteries when USB is connected, preventing back-feeding.

=== Microcontroller Section ===

40-pin socket for [[Raspberry Pi Pico]] or compatible boards:
* Raspberry Pi Pico (official or clone)
* Raspberry Pi Pico W (adds Wi-Fi)
* Raspberry Pi Pico 2 / 2W (RP2350-based)

The socket allows easy replacement if the Pico is damaged, and permits swapping between different Pico variants.

=== Motor Control Section ===

[[File:PCB_motor.png|thumb|300px|Motor driver section]]

Two options for motor control:

==== Option 1: TB6612FNG Module (Standard) ====

* Solder [[TB6612FNG]] breakout module directly to PCB
* Controls two TT motors independently
* PWM speed control via Pico GPIOs
* Direction control via logic pins

==== Option 2: External H-Bridge (Advanced) ====

* Install 2×5 DuPont header underneath TB6612FNG footprint
* Provides PWM, direction, and logic signals to external H-bridge
* Allows use of higher-power motor drivers
* '''Same Python code works''' - control signals are identical

This flexibility allows SimpleBot to be upgraded to more powerful motors without redesigning electronics or software.

=== Optical Encoder Section ===

[[File:PCB_Optoencoder.png|thumb|300px|Optical encoder circuit]]

The odometry section uses [[LM393]] dual comparator to convert analog encoder signals to digital pulses:

* '''Per Channel''':
** 1× IR LED (emitter)
** 1× Photoresistor (detector)
** Voltage divider resistors
** Comparator output to Pico GPIO

* '''Function''':
# LED shines through slotted encoder wheel
# Photoresistor detects light/dark transitions
# LM393 converts analog voltage to clean digital pulses
# Pico counts pulses using interrupts
# Software calculates distance traveled

This provides '''optical odometry''' for dead reckoning and position tracking.

=== Expansion Headers ===

==== nRF24L01 Radio (SPI) ====

* 2.4 GHz wireless communication
* SPI interface (SCK, MOSI, MISO, CS)
* Range: 10-100m depending on antenna and environment
* Use cases: Remote control, swarm robotics, telemetry

==== MPU6050 IMU (I²C) ====

* 3-axis accelerometer + 3-axis gyroscope
* I²C interface (SDA, SCL)
* Heading estimation, tilt detection, dynamic balancing

==== Sensor Headers (4×) ====

Each header provides:
* 3.3V power
* Ground
* GPIO pin from Pico

Use for:
* Additional line sensors
* Ultrasonic distance sensors
* Bump switches
* Custom sensors

==== Analog/Digital Expansion ====

* '''Analog Header''': 3× ADC pins for custom analog sensors
* '''Digital Header''': Multiple GPIO pins for digital I/O

== PCB Layout ==

=== Top View ===
[[File:PCB_front.png|thumb|300px|PCB top side (component placement)]]

The top side contains:
* All component footprints
* Module sockets (Pico, TB6612FNG, MP1584)
* Expansion headers
* Power and motor terminals

=== Bottom View ===
[[File:PCB_back.png|thumb|300px|PCB bottom side (traces and ground plane)]]

The bottom side contains:
* Signal traces
* Ground plane (for noise reduction and current return)
* Minimal components (optional pull-up resistors)

=== All Layers ===
[[File:PCB_all_layers.png|thumb|300px|Complete PCB stack-up]]

The 2-layer design uses:
* '''Top Layer''': Signal routing and power traces
* '''Bottom Layer''': Ground plane + additional signal routing

== Bill of Materials ==

{| class="wikitable"
! Component !! Description !! Qty !! Notes
|-
| colspan="4" style="background-color: #e0e0e0; font-weight: bold;" | '''Modules'''
|-
| [[Raspberry Pi Pico]] || Microcontroller board || 1 || Or Pico W for Wi-Fi
|-
| [[TB6612FNG]] Module || Dual H-bridge motor driver || 1 || Or external H-bridge
|-
| [[MP1584]] Module || Buck converter || 1 || Pre-tune to 3.3V!
|-
| colspan="4" style="background-color: #e0e0e0; font-weight: bold;" | '''ICs'''
|-
| [[LM393]] || Dual comparator IC || 1 || DIP-8 package
|-
| colspan="4" style="background-color: #e0e0e0; font-weight: bold;" | '''Passive Components'''
|-
| Resistors || Various values for encoders and pull-ups || ~10 || See schematic
|-
| IR LEDs || Encoder emitters (940nm) || 2 || Through-hole
|-
| Photoresistors || Encoder detectors || 2 || Through-hole
|-
| colspan="4" style="background-color: #e0e0e0; font-weight: bold;" | '''Connectors'''
|-
| 40-pin header || Pico socket || 2 || Female, 2×20
|-
| Motor terminals || Screw terminals or header || 2 || 2-pin each
|-
| Power terminals || Battery input || 1 || 2-pin screw terminal
|-
| Sensor headers || Expansion connections || 4 || 3-pin male header
|-
| colspan="4" style="background-color: #e0e0e0; font-weight: bold;" | '''Optional'''
|-
| nRF24L01 header || Radio module socket || 1 || 2×4 female header
|-
| MPU6050 header || IMU socket || 1 || 2×4 female header
|-
| DuPont header || External H-bridge || 1 || 2×5 male header
|}

Full BOM with part numbers and suppliers available in the [https://github.com/Bespoke-Robot-Society/simplebot GitHub repository].

== Assembly Guide ==

=== Assembly Order ===

# '''Pre-tune buck converter''' to 3.3V (CRITICAL!)
# Install low-profile components (resistors, ICs)
# Install sockets and headers
# Install modules (buck converter, TB6612FNG)
# Test voltage output before connecting Pico
# Insert Pico into socket
# Connect motors and sensors
# Upload code and test!

Full step-by-step assembly instructions: [[SimpleBot PCB Guide]] or [https://github.com/Bespoke-Robot-Society/simplebot/blob/master/PCB_GUIDE.md GitHub version]

=== Critical Steps ===

==== 1. Buck Converter Adjustment ====

'''DO THIS FIRST''':
# Connect multimeter to buck converter output
# Apply power to buck converter input
# Adjust potentiometer to exactly 3.3V
# Verify voltage is stable
# ONLY THEN solder to PCB

'''Failure to do this can damage your Pico!'''

==== 2. Test Before Connecting Pico ====

After soldering the buck converter:
# Apply battery power (do NOT connect Pico yet)
# Verify 3.3V on all power rails
# Check for shorts with multimeter
# Only after confirming correct voltage, insert Pico

== Manufacturing Files ==

=== Gerber Files ===

Ready-to-manufacture Gerber files available:
* '''[https://github.com/Bespoke-Robot-Society/simplebot/blob/master/diffdrive_robot_microcontroller_board--tht_Gerber.zip Through-Hole Version]''' - Beginner-friendly THT components
* SMT version (coming soon) - Compact surface-mount design

=== PCB Specifications ===

* '''Dimensions''': ~90mm × 70mm (approximate)
* '''Layers''': 2-layer PCB
* '''Thickness''': 1.6mm (standard)
* '''Material''': FR-4
* '''Surface Finish''': HASL or ENIG
* '''Min Trace/Space''': 0.3mm / 0.3mm
* '''Min Drill''': 0.8mm

=== Ordering ===

Upload the Gerber ZIP file to any PCB manufacturer:
* '''JLCPCB''' - ~$2 for 5 PCBs + shipping
* '''PCBWay''' - ~$5 for 5 PCBs + shipping
* '''OSH Park''' - ~$20 for 3 PCBs (US-based, high quality)
* '''Seeed Studio''' - ~$5 for 5 PCBs + shipping

Manufacturing typically takes 2-5 days + shipping time.

== Design Files ==

The PCB was designed in '''KiCad''' (open-source EDA software):

* '''Schematic''': Full circuit diagram in KiCad format
* '''PCB Layout''': Complete board design with traces and copper pours
* '''Gerber Files''': Manufacturing-ready outputs
* '''Bill of Materials''': Component list with part numbers

All files available in the [https://github.com/Bespoke-Robot-Society/simplebot GitHub repository] under open-source license.

== Usage in Projects ==

=== SimpleBot ===

This PCB was designed specifically for [[SimpleBot]], but the design is generic enough for any differential drive robot with:
* Two DC motors
* Wheel encoders
* Line sensors or similar digital/analog sensors
* Battery power (4.5V – 6.5V input)

=== Other Robots ===

The modular design makes this PCB suitable for:
* Line-following robots
* Maze-solving robots
* Dead-reckoning navigation platforms
* Educational robotics projects
* Small autonomous vehicles

== Variations ==

=== External H-Bridge Variant ===

Install the 2×5 DuPont header instead of TB6612FNG module to use external motor drivers:
* '''L298N''' - Lower efficiency but higher current
* '''BTS7960''' - Much higher current (43A!) for large motors
* '''Cytron MD30C''' - High power with heat sink

Same Pico code works with all drivers - only change is physical wiring.

=== Custom Sensor Configurations ===

Use the sensor headers for:
* Additional line sensors (6-8 sensor arrays)
* Ultrasonic sensors (HC-SR04)
* IR distance sensors (Sharp GP2Y0A)
* Bump switches
* Servo motor control

=== Future Variants ===

* '''SMT Version''' - All surface-mount components for compact design
* '''High-Power Version''' - Integrated high-current motor driver
* '''All-in-One Version''' - Integrated sensors (no external modules)

== See Also ==

* [[SimpleBot]] - Robot using this PCB
* [[Raspberry Pi Pico]] - Microcontroller platform
* [[TB6612FNG]] - Motor driver
* [[MP1584]] - Buck converter
* [[LM393]] - Comparator IC
* [[PCB Design]] - General PCB design guide
* [[KiCad]] - PCB design software tutorial

== Resources ==

* [https://github.com/Bespoke-Robot-Society/simplebot GitHub Repository] - Design files, Gerbers, BOM
* [https://github.com/Bespoke-Robot-Society/simplebot/blob/master/PCB_GUIDE.md PCB Assembly Guide] - Detailed assembly instructions
* [[Soldering Guide]] - Learn through-hole soldering techniques

[[Category:PCB]]
[[Category:Motor Control]]
[[Category:Robot Electronics]]

BRS Differential Drive Robot Control Board - Revision history

John at 20:32, 11 October 2025

John: Claude edited based on my notes, prompt, and SimpleBot code repository