By name: hardware-safety description: Hardware safety rules for the WIM-Z robot. Automatically relevant when modifying motor control, servo code, power management, GPIO pins, or any hardware interface code.
WIM-Z Hardware Safety Rules
CRITICAL — Read Before Any Hardware Code Changes
Motor Safety
- Max PWM: 75% duty cycle (9V effective) — ABSOLUTE MAXIMUM
- Safe range: 40-70% duty cycle
- NEVER use 100% duty cycle — would supply 12.6V to 6V-rated motors
- Rate limiting: 50ms minimum between motor commands
- Always implement gradual ramp-up/down — no instant full-speed transitions
Servo Safety (PCA9685)
- Channel 0: Camera Pan (0°-270°, center=140°)
- Channel 1: Camera Tilt (20°-200°, horizon=50°)
- Channel 2: Treat Carousel — CONTINUOUS ROTATION servo
- Use
pulse_to_duty(1700)for dispensing, NOTkit.servo[2].angle - Duration: 50ms per treat
- Always use
stop_carousel(gradual=True)— abrupt stop causes screech
- Use
Power System
- Battery: 4S2P Li-ion, 14.8V nominal (12V min, 16.8V max)
- Pi power: 5V @ 5A via buck converter — never draw from GPIO 5V pin
- NeoPixel power: Separate 5V buck converter — not shared with Pi
GPIO Rules
- Pin 10 (GPIO10/MOSI): NeoPixel signal — do not reassign
- Pin 25 (GPIO25): Blue LED MOSFET — do not reassign
- Pins 7,16,23,29,31: Encoder pins — do not reassign
- Pins 11,12,13,15,33,35: Motor control PWM — do not reassign
- Pins 3,5: I2C (PCA9685) — do not reassign
Before Deploying Hardware Changes
- Review GPIO pin assignments against the mapping in hardware_specs.md
- Verify PWM duty cycle is within safe range
- Test servo movements with small increments first
- Check battery voltage before running motor tests
- Have physical access to the power switch during testing