How to Select Components for Robotics Projects

How to Select Components for Robotics Projects

Robotics projects fail most often not because of programming errors, but because of mismatched components — a motor driver rated at 2A paired with a motor that draws 3A stall current, or a battery that sags under load. This guide walks through each component category with the right questions to ask before buying.

Chassis and Mechanical Structure

For beginner robots, the standard 4WD or 2WD acrylic robot chassis kits (₹200–400) include motors, wheels, motor brackets, and an acrylic plate. These are adequate for line followers, obstacle avoiders, and WiFi-controlled bots. For heavier payloads or rough terrain, aluminium chassis kits (₹600–1,200) provide more rigidity.

Key question: what is the total weight of your robot including battery and electronics? A typical 4WD bot with ESP32, sensors, and 3S LiPo weighs 500–800g. Your motors need to move this weight plus any payload.

DC Motors and Gear Ratios

Standard yellow TT gear motors (BO motors) used in most beginner kits: 3–6V, ~150 RPM at 6V, stall current ~600 mA. They are adequate for lightweight bots on smooth floors. For heavier robots or rough terrain, use N20 gear motors (6V, 100–300 RPM, 1.2 kg·cm torque, ~600 mA stall) or Johnson motors.

Gear ratio determines speed vs torque. Lower RPM = higher torque. A robot that needs to climb ramps needs more torque (lower RPM, higher gear ratio) than a fast line follower.

Servo Motors

For robotic arms, camera gimbals, and steering mechanisms. The SG90 (9g, plastic gears, ₹60–90) handles loads up to ~1 kg·cm. The MG996R (metal gears, ₹180–250) handles up to 10 kg·cm. Use MG996R for any joint carrying structural load — the SG90 strips its plastic gears under stress. Both operate at 4.8–6V on the signal wire (3.3V pulse compatible).

Motor Drivers

Never connect motors directly to microcontroller GPIO pins — GPIO pins supply 40 mA max, motors draw 500 mA+. Always use a motor driver IC.

• L298N dual H-bridge module: 2A per channel, 5–35V, drives two DC motors or one stepper. PWM speed control. Price: ₹100–150. The standard for beginner robots. Note: drops 2V across the H-bridge, reducing effective motor voltage.
• TB6612FNG: 1.2A continuous per channel, only 0.5V drop, more efficient than L298N. Ideal for battery-powered robots where efficiency matters. Price: ₹80–130.
• L293D: Older, less efficient, 600 mA per channel — sufficient only for very light loads. Not recommended for new designs.
• DRV8833: 1.5A per channel, very compact, 0.35V drop. Excellent for mini robots.

Sensors for Robotics

• Line following: TCRT5000 IR reflectance sensor array (typically 5-sensor array, ₹80–150). Reads reflected IR from white/dark surfaces.
• Obstacle detection: HC-SR04 ultrasonic (front, ₹40–70) or Sharp GP2Y0A21 IR (₹200–350) for closer-range detection.
• Edge detection: TCRT5000 facing downward at chassis corners — prevents falling off tables.
• Orientation: MPU-6050 6-axis IMU (₹60–100) for balance bots, slope detection, and turn angle measurement.
• Encoders: Hall effect encoders (₹50–100/pair) on motor shafts for precise odometry and closed-loop speed control.

Controllers

• Arduino Nano: Best for simple bots — line follower, obstacle avoider. Simple code, 5V logic, well-documented. ₹150–200.
• ESP32: Use when you need WiFi/BT control, camera vision (ESP32-CAM), or multi-core processing for sensor fusion. ₹280–350.
• Raspberry Pi (any model): Use for computer vision bots, ROS-based platforms, or when you need Linux. Overkill for simple bots, necessary for complex ones.

Battery Selection

A 2S (7.4V) or 3S (11.1V) LiPo battery provides the best power density for robots. Common choices: 2200 mAh 2S LiPo for a 4WD bot (₹500–800). Ensure the LiPo discharge rate (C rating) × capacity exceeds your peak current draw: a 1000 mAh 20C battery can deliver 20A peak — more than enough for most bots.

Use a LiPo alarm (₹40–60) to alert when voltage drops below 3.3V per cell — preventing deep discharge that permanently damages LiPo cells.

All motor drivers, sensors, and ESP32 boards are available at Circuitkar's robotics and motors section.