Servo sweep with RPi.GPIO PWM on a Raspberry Pi 4
RPi.GPIO software PWM at 50 Hz on a Raspberry Pi 4: a servo on GPIO18 steps from 0 to 180 degrees and back, one position a second. The whole build, a Raspberry Pi 4 and 1 more part, runs here in your browser on the Python below; open it in the editor to change the wiring or the code and run it again.
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The parts retail for about $58. On Mokxi they're free.
The code
The Python exactly as the editor opens it. Change a line there and press Run: the board runs main.py in a Python engine in the page, with gpiozero and RPi.GPIO, and nothing to compile.
# Sweep a servo with RPi.GPIO's software PWM on a Raspberry Pi 4.
# Signal on GPIO18 (pin 12), power from 5V (pin 2), ground on pin 6.
import RPi.GPIO as GPIO
import time
SERVO = 18
GPIO.setmode(GPIO.BCM)
GPIO.setup(SERVO, GPIO.OUT)
pwm = GPIO.PWM(SERVO, 50) # 50 Hz: one pulse every 20 ms
def angle_to_duty(angle):
# This servo reads a 0.544 ms pulse as 0 degrees and 2.4 ms as 180.
pulse_ms = 0.544 + angle / 180 * 1.856
return pulse_ms / 20 * 100 # the pulse as a percentage of the 20 ms frame
pwm.start(angle_to_duty(90))
try:
while True:
for angle in (0, 45, 90, 135, 180):
pwm.ChangeDutyCycle(angle_to_duty(angle))
print(f"{angle} degrees: {angle_to_duty(angle):.2f}% duty")
time.sleep(1)
except KeyboardInterrupt:
pwm.stop()
GPIO.cleanup()
Parts list
2 parts, plus the jumper wires. They retail for about $58; on Mokxi they're free.
How it is wired
3 connections, pin by pin, read from the circuit itself. Each line is one set of pins joined together, by a jumper wire or a breadboard strip.
- Raspberry Pi 4 Model B pin 5V; Hobby servo pin VCC
- Ground: Raspberry Pi 4 Model B pin GND; Hobby servo pin GND
- Raspberry Pi 4 Model B pin GPIO18; Hobby servo pin PWM
Change it and keep it
Open it in the editor, change the circuit or the code, and keep your version in a free account.