Overview

The power system is designed for portability and sufficient runtime for daily use. A 7.4V 1500mAh 2S LiPo battery provides the primary power source, with two DC-DC buck converters stepping down to 6V (servos) and 5V (Raspberry Pi, Arduino, analog front-end). Total current draw varies with activity:

• Idle (no actuation): ~400 mA (Pi Zero: 150 mA, Pico: 50 mA, Arduino: 30 mA, servos idle: 4 × 40 mA)
• Active grasping: ~1500 mA (servos under load: 4 × 250 mA, plus control electronics)
• Peak (all servos stalled): ~2500 mA (brief, thermal limits apply)

Assuming 50% duty cycle (intermittent grasping), average current is ~800 mA, yielding approximately 1.8 hours runtime. For extended use, a higher-capacity battery (e.g., 2200mAh) can be substituted without design changes.

Power Distribution Diagram

Block diagram showing battery, regulators, and distribution to subsystems.

Design Notes

• •Voltage selection: 6V for servos balances torque and heat; 5V for logic ensures Arduino/Pi compatibility.
• •Regulators: LM2596 handles servo current spikes (3A max); MP1584 provides stable 5V for sensitive electronics.
• •Battery protection: LiPo includes built-in protection circuit module (PCM) to prevent over-discharge below 3.0V/cell.
• •Charging: External LiPo balance charger (not integrated). Charge at 1C (1.5A) for ~1 hour from empty.
• •Thermal management: Buck converters mounted on aluminum heat spreader; servos include built-in thermal cutoff.

Bill of Materials (Power)