import RPi.GPIO as GPIO
import time
GPIO.setmode(GPIO.BOARD)
GPIO.setup(7,GPIO.OUT)
p=GPIO.PWM(7,50)
p.start(7.5)
while True:
	p.ChangeDutyCycle(7.5)
	time.sleep(1)
	
	p.ChangeDutyCycle(2.5)
	time.sleep(1)
p.stop()
GPIO.cleanup()
