servo_sweep.py
An SG90-class servo is driven with 50 Hz PWM on GPIO18 (pin 12) via gpiozero PWMOutputDevice: value=0 means 0 degrees, value=1 means 180. The script sweeps continuously. Mind the power budget: modèle A sans Ethernet : alimentation 5 V/700 mA via l'OTG, hub USB alimenté pour les périphériques; power servos separately beyond two.
Hardware
A Raspberry Pi Model A (BCM2835, 26-pin GPIO header, a single OTG-mode USB port, no Ethernet: plan for a powered USB hub). One SG90 micro-servo (or similar), an external 5 V supply recommended, dupont wires.
Wiring
Orange/yellow signal wire to GPIO18 (pin 12), brown/red to 5 V, black/yellow to GND shared with the board.
How it works
PWMOutputDevice emits a 50 Hz pulse train, 0.5–2.5 ms wide; the servo angles its horn with the pulse width.
Running it
Copy the script to the board (scp or USB stick), then run it with python3 (or bash). On older Raspbian, install gpiozero with sudo apt install python3-gpiozero. Power the board at 5 V/700 mA minimum through the OTG port.
Variants
Use gpiozero Servo(angle) for a degree API; two servos make an XY tracker. Power through the OTG port at 5 V/700 mA minimum; avoid power-hungry USB devices.
servo_sweep.py
# servo_sweep.py — balaie un micro-servo (SG90) de 0 a 180 degres.
# Deps: sudo apt install python3-gpiozero
from gpiozero import PWMOutputDevice
from time import sleep
servo = PWMOutputDevice(18, frequency=50, pulse_width=0.001)
print("Balayage servo, Ctrl+C pour sortir")
try:
while True:
for deg in range(0, 181, 15):
servo.value = deg / 180.0
sleep(0.05)
for deg in range(180, -1, -15):
servo.value = deg / 180.0
sleep(0.05)
except KeyboardInterrupt:
servo.off()
print("Arret")