Now le me read the python program to refresh my memory.# relay toggle test 2019jan10 tlfong01 2019jan109hkt1625 ***
    # Rpi3B+ stretch (Linux 4.14.34-v7+ arm) IDLE python 3.5.3 
    
    # Program Description
    # 1. Setup Rpi.GPIO BCM mode
    # 2. Set GPIO11 as relayPin to control 5V relay KY019
    # 3. Toggle 100 times relayPin at 1Hz
    
    import RPi.GPIO as GPIO
    from   time import sleep
    
    # *** GPIO Functions ***
    
    def setGpioMode():
        GPIO.setwarnings(False) 
        GPIO.setmode(GPIO.BCM)
        return
    
    # *** Set Gpio pin as output ***
    
    def setGpioPinOutput(gpioPin):
        GPIO.setup(gpioPin, GPIO.OUT)
        return
    
    # *** Set Gpoio pin High/Low ***
    
    def setGpioPinHigh(gpioPin):  
        GPIO.output(gpioPin, GPIO.HIGH)
        return
    
    def setGpioPinLow(gpioPin): 
        GPIO.output(gpioPin, GPIO.LOW)
        return
    
    # *** Toggle Gpio pin ***
    
    def toggleGpioPin(gpioPin, highSecond, lowSecond, count): 
        for i in range(count):
            setGpioPinHigh(gpioPin)
            sleep(highSecond)
            setGpioPinLow(gpioPin)
            sleep(lowSecond)
        return
    
    # *** Main ***
    
    print('Begin togglePin(), ...')
    
    relayPin   = 11
    highSecond = 1
    lowSecond  = 1
    count      = 100
    
    setGpioMode()
    setGpioPinOutput(relayPin)
    
    toggleGpioPin(relayPin, highSecond, lowSecond, count)
    
    print('End   togglePin().')
    
    # *** End ***