why simple led python program not working

Question

I am testing my pi for the first time and i cant able to run the first program to light the led.

below is my code id from raspberry cookbook

import Rpi.GPIO as GPIO
import time

GPIO.setmode(GPIO.BCD)
GPIO.setup(18,GPIO.OUT)
while(True):
GPIO.output(18, True)
time.sleep(1)
GPIO.output(18,False)
time.sleep(1)

when i run the script sudo python led.py it shows no error but the led has no output. I tried connecting a 360ohms between pin 18 and led. also tried connecting 540Ohms between pin 18 and led but no result.

Can anyone suggest how to debug the problem

do you have the lines after while(True): properly indented? Make sure there is consistent indenting (whitespace) after each line you want repeated — omu_negru
– omu_negru, Commented Mar 17, 2015 at 18:29
Hmm. Raspberry's GPIO is 3.3 V. Not many LEDs light up on such a low voltage. Try a red one or test with a meter, and be sure not to pull too much current out (use an appropriate resistor and a dim enough LED). — Fran Borcic
– Fran Borcic, Commented Mar 17, 2015 at 18:47
Instead of True or False, use HIGH or LOW also. Pretty sure they don't correlate. — Shawnic Hedgehog
– Shawnic Hedgehog, Commented Mar 17, 2015 at 18:57

Foon · Accepted Answer · 2015-03-17 18:31:21Z

1

You should probably (and I don't know if either main stack or the EE-centric or the RPi spinoffs has a good way to do this inline) include some sort of diagram showing which pins you're connecting. At a minimum, you need to do GPIO 18 to LED to GND, and as LED is Light Emitting Diode or something to that effect, you need to make sure your LED is pointing in the correct direction. I'd suggest as a way to debug this partially, take python out of the loop and just configure the LED to be always on by writing a 1 to the appropiate /sys/blah/path. Also, http://elinux.org/RPi_Low-level_peripherals#sysfs (which has the path you need) points out... GPIO 24 is wired to P1_18 so you might want to double check that the pin you think is 18 is called 18 on both sides of the system.

answered Mar 17, 2015 at 18:31

Foon

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nagordon · Accepted Answer · 2015-03-18 14:26:18Z

1

This should blink the light on and off and worked for me

from time import sleep
import RPi.GPIO as gpio
gpio.setmode(gpio.BCM)
gpio.setup(18, gpio.OUT)
gpio.output(18, True)
sleep(5)
gpio.output(18, False)

answered Mar 18, 2015 at 14:26

nagordon

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romy mathew · Accepted Answer · 2015-03-19 02:43:48Z

1

Thanks all for the comments and suggestion, when I added the GPIO.clearup() and restarted the system it starts blinking....

below is the comeple code i used...

import Rpi.GPIO as GPIO
import time

GPIO.setmode(GPIO.BCD)
GPIO.setup(18,GPIO.OUT)

while(True):

       GPIO.output(18, GPIO.HIGH)
       time.sleep(1)
       GPIO.output(18,False)
       time.sleep(1)

GPIO.CLEARUP()

THANKS EVERYONE FOR THE HELP....

answered Mar 19, 2015 at 2:43

romy mathew

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