GPIO is not working, 5V working, 3.3 V working, Raspberry Pi B+

Question

I am the RPi B+ user. Feeling confused about the GPIO. GPIO isn't working. I tried checking it with multimeter by connecting the pin 21 to the gnd, not work. And then i tried the 5 v and 3.3 v, it works. Any idea about this problem. I am working a project using RPi. So i need to solve it immidiately. I am a newbie abou RPi.

import RPi.GPIO as GPIO
from time import sleep
GPIO.setmode(GPIO.BCM)
GPIO.setup(21, GPIO.OUT)
GPIO.output(21, 1)
GPIO.cleanup()

Anyway GPIO 21 in the seventh left gpio?? Need Help!! Thanks

Answer 1

As you can see here http://pi.gadgetoid.com/pinout/gpio GPIO 21 on the right at the bottom. You are connecting it to wrong pin

Answer 2

gpio21 was at pin 13 in the first revision of the original Pi. In all recent models gpio27 is at pin 13.

Where two gpios are shown (x/y) the second gpio is used in current models. V indicates a voltage and that the pin is part of the power rail.

           pin  pin
3V3         1    2      5V
0/2 (SDA)   3    4      5V
1/3 (SCL)   5    6      0V
4           7    8      14 (TXD)
0V          9   10      15 (RXD)
17 (ce1)   11   12      18 (ce0)
21/27      13   14      0V
22         15   16      23
3V3        17   18      24
10 (MOSI)  19   20      0V
9 (MISO)   21   22      25
11 (SCLK)  23   24      8 (CE0)
0V         25   26      7 (CE1)
           .......
0 (ID_SD)  27   28      1 (ID_SC)
5          29   30      0V
6          31   32      12
13         33   34      0V
19 (miso)  35   36      16 (ce2)
26         37   38      20 (mosi)
0V         39   40      21 (sclk)

Answer 3

No dude, your code will turn the LED on for a millisecond and then the script will close. Put it in a While True: loop.

Example with sleep

import RPi.GPIO as GPIO
from time import sleep
GPIO.setmode(GPIO.BCM)
GPIO.setup(21, GPIO.OUT)
GPIO.output(21, 1)
time.sleep(10)
GPIO.cleanup()