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: révision 2 : alimentation micro-USB/OTG soignée, connecteur 26 broches (pas de 40 broches); power servos separately beyond two.
Hardware
A Raspberry Pi Model B revision 2 (BCM2835, 26-pin GPIO header, Ethernet/USB ports moved to the board edge). 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 Raspbian, install gpiozero with sudo apt install python3-gpiozero. The full 26-pin pinout is in the official Raspberry Pi schematic.
Variants
Use gpiozero Servo(angle) for a degree API; two servos make an XY tracker. Revision 2: a clean 5 V supply is required; brown-outs distort sensor readings.
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")