import time

import RPi.GPIO as GPIO


GPIO.setwarnings(False)

GPIO.setmode(GPIO.BCM)

GPIO.setup(4, GPIO.OUT)



#delay = delay0   = 0.0006

#delay = delay90  = 0.0014

delay  = delay180 = 0.0020



for x in xrange(0, 50):
        
	GPIO.output(4, 1)
        
	time.sleep(delay)
        
	GPIO.output(4, 0)
        
	time.sleep(0.02-delay)

