Pololu 3675 Gearmotor and Encoder Assembly for Romi/TI-RSLK MAX
Pololu 3675 Gearmotor and Encoder Assembly for Romi/TI-RSLK MAX
Pololu 3675 Gearmotor and Encoder Assembly for Romi/TI-RSLK MAX
The Pololu 3675 is a precision gearmotor and integrated quadrature encoder assembly specifically designed for the Romi chassis and TI-RSLK MAX robotics platforms. This assembly combines a high-efficiency brushed DC motor with a 50:1 gear reduction and a dual-channel encoder providing 12 counts per motor shaft revolution for accurate odometry and motor control feedback. Professional roboticists, educational institutions, and autonomous systems developers rely on this component to achieve precise speed regulation, accurate distance measurement, and reliable motor performance in mobile robot applications.
Product Overview
The Pololu 3675 Gearmotor and Encoder Assembly integrates a miniature brushed DC motor with a compact plastic gearbox and a magnetic quadrature encoder on a single integrated unit. The motor operates at 3V to 6V nominal voltage, delivering approximately 70 RPM output shaft speed at 4.5V with a 50:1 gear ratio. The integrated encoder uses Hall effect sensors to generate two-phase quadrature signals, enabling closed-loop motor control and precise position tracking essential for robot navigation and odometry calculations. The assembly is pre-mounted on the Romi chassis connector interface, eliminating complex wiring and mechanical alignment challenges.
This gearmotor assembly excels in applications requiring bidirectional rotation, smooth acceleration profiles, and accurate speed feedback. The 50:1 reduction ratio provides excellent torque characteristics while maintaining sufficient speed for mobile robot locomotion at typical operating voltages. The encoder output directly interfaces with microcontroller GPIO pins or dedicated quadrature decoder circuits, making integration straightforward with platforms like Arduino, TI MSP430, and ARM Cortex-M processors. The sealed gearbox design protects internal components from dust and debris, ensuring reliable long-term operation in educational and field robotics environments.
Key Specifications
| Specification | Details |
| Product Type | Gearmotor with Integrated Quadrature Encoder Assembly |
| Brand | Pololu Robotics and Electronics |
| Model Number | 3675 |
| Origin | Original/Authentic |
| Warranty | 7 days on manufacturing defects |
| Shipping | 1-5 days from Bengaluru |
| Delivery | 7-8 days across India |
| Support | 24/7 via Email and WhatsApp |
| Motor Type | Brushed DC Motor with Plastic Gearbox |
| Gear Ratio | 50:1 |
| Operating Voltage | 3V to 6V DC (4.5V nominal) |
| Output Speed | Approximately 70 RPM at 4.5V |
| Encoder Resolution | 12 counts per motor shaft revolution |
| Encoder Type | Magnetic Quadrature Encoder with Hall Effect Sensors |
| Output Shaft Diameter | 3mm |
| Connector Interface | Romi Chassis Compatible |
Key Features
- Integrated Quadrature Encoder: Dual-channel Hall effect encoder generates 12 counts per motor shaft revolution, enabling accurate speed measurement and position tracking for odometry calculations in mobile robots.
- 50:1 Gear Reduction: Provides optimal torque and speed balance for wheeled robot locomotion while maintaining smooth acceleration and deceleration profiles across typical operating voltage ranges.
- Romi Chassis Optimized: Pre-designed connector interface eliminates custom wiring and mechanical fabrication, reducing assembly time and integration complexity for educational robotics platforms.
- Wide Voltage Range: Operates reliably from 3V to 6V DC, accommodating various battery configurations and power management schemes common in portable robotics systems.
- Sealed Gearbox Design: Protective housing shields internal gears and bearings from environmental contamination, ensuring consistent performance in field robotics and outdoor autonomous systems.
- Bidirectional Rotation: Supports forward and reverse motor control through standard H-bridge motor driver circuits, enabling differential drive steering and complex motion patterns.
Applications and Use Cases
- Educational Robotics Platforms: Ideal for university-level robotics courses, FIRST Robotics competitions, and maker education programs requiring reliable motor feedback for closed-loop control demonstrations.
- Autonomous Mobile Robots: Provides essential odometry feedback for simultaneous localization and mapping (SLAM) algorithms, dead reckoning navigation, and obstacle avoidance in indoor autonomous systems.
- TI-RSLK MAX Robot Development: Purpose-built for Texas Instruments Robotics Systems Learning Kit, enabling students to implement advanced motor control algorithms and sensor fusion techniques.
- Differential Drive Wheeled Robots: Dual gearmotor assemblies with synchronized encoder feedback enable precise differential steering control, essential for line-following robots and maze navigation challenges.
- Robot Speed Regulation: Encoder feedback supports PID control loops for maintaining constant velocity despite varying load conditions, battery voltage fluctuations, and surface friction variations.
- Position Tracking and Odometry: Cumulative encoder counts enable accurate wheel rotation counting and distance traveled calculations, fundamental for robot localization without external positioning systems.
How to Use
Begin by mounting the Pololu 3675 gearmotor assembly onto your Romi chassis or TI-RSLK MAX platform using the provided connector interface and mechanical brackets. Ensure the output shaft is properly aligned with your wheel hub and that the assembly is securely fastened to prevent mechanical slippage during operation. Connect the motor power leads to your H-bridge motor driver circuit, typically an L298N, DRV8835, or integrated motor control module. The encoder output pins should be connected to interrupt-capable GPIO pins on your microcontroller to capture rising and falling edges of the quadrature signals.
Configure your microcontroller firmware to read encoder signals using external interrupt handlers or dedicated quadrature decoder peripherals. Implement a counter variable that increments or decrements based on the direction of motor rotation determined by the phase relationship between the two encoder channels. For closed-loop speed control, measure the encoder count rate over fixed time intervals to calculate actual motor speed, then compare against your desired setpoint using a PID controller to adjust motor voltage accordingly. Calibrate your odometry calculations by measuring the actual distance traveled per encoder count, accounting for wheel diameter variations and gear ratio tolerances specific to your assembled unit.
Frequently Asked Questions
What is the encoder resolution and how does it affect odometry accuracy?
The Pololu 3675 encoder generates 12 counts per motor shaft revolution. With a 50:1 gear ratio, this translates to 600 counts per output shaft revolution. For odometry calculations, divide the cumulative encoder count by 600 and multiply by your wheel circumference to determine distance traveled. Higher resolution encoders provide better accuracy but require faster microcontroller interrupt handling. The 12-count resolution is sufficient for typical mobile robot applications with wheels 65-75mm in diameter.
Can I use this gearmotor with voltages outside the 3V to 6V range?
Operating the Pololu 3675 outside the specified 3V to 6V range may damage the motor windings or cause encoder malfunction. Voltages below 3V provide insufficient torque for robot locomotion, while voltages above 6V risk permanent motor damage and reduced lifespan. If your power system requires different voltage levels, use a buck converter to step down higher voltages or implement PWM voltage regulation within the specified range. Always verify your power supply specifications before connecting to the motor assembly.
How do I implement closed-loop motor speed control using the encoder feedback?
Implement a PID control loop by measuring encoder count increments over fixed time intervals (typically 10-50ms) to calculate actual motor speed in counts per second. Compare this measured speed against your desired setpoint and calculate the error. Use a PID algorithm to adjust the PWM duty cycle sent to your motor driver based on proportional, integral, and derivative error terms. Start with conservative PID gains (Kp=0.5, Ki=0.1, Kd=0.1) and tune empirically by observing motor response to step changes in setpoint. This approach compensates for battery voltage variations, load changes, and mechanical friction automatically.
What is the maximum torque output of this gearmotor assembly?
The Pololu 3675 produces approximately 0.3 Nm of continuous torque at 4.5V with the 50:1 gear reduction. Peak torque during stalled conditions reaches approximately 0.5 Nm, though sustained stall operation should be avoided to prevent motor overheating. The actual torque available depends on supply voltage and motor current draw, typically 200-400mA under normal operating conditions. For applications requiring higher torque, consider using dual motors with differential drive configuration or selecting higher-voltage Pololu gearmotor variants.
How should I connect the encoder output pins to my microcontroller?
The encoder generates two quadrature signals (Channel A and Channel B) that must be connected to interrupt-capable GPIO pins on your microcontroller. Connect one channel to an external interrupt pin and configure it to trigger on rising edges. In the interrupt handler, read the state of the second channel to determine rotation direction: if both channels are high, the motor is rotating forward; if only the first channel is high, it is rotating backward. Alternatively, use dedicated quadrature decoder peripherals available on many microcontroller platforms for more efficient signal processing without software overhead.
When will I receive my order?
Orders are dispatched within 1-5 business days from our Bengaluru warehouse. Delivery takes 7-8 days to most locations across India.
What is your return and warranty policy?
We offer a 7-day return policy on manufacturing defects only. Contact support within 7 days of receipt for free replacement or full refund. Not applicable for user damage or misuse.
Are bulk discounts available?
Yes, wholesale pricing for orders of 10 or more units. Contact our sales team via WhatsApp or email for a customized bulk quote.
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