Relay is off when GPIO is set to high(True) and vice versa

[ikequan]

Hello pals. This is my first post and i hope i have posted in the right place.
I'm working on a project which i intend to turn light on/off using my raspberry pi and a 5v 8 ch replay. I followed some steps online to setup my raspberry pi and relay but when i set the GPIO(pin 7) to high(true) the replay turns off and when the GPIO is set to low(false) the replay turn on. Below is how i did my setup
1. RPI pin 4 to VCC pin of replay
2. RPI pin 6 to GND pin of replay
3. RPI pin 7 to IN1 pin of replay

Please am using raspberry pi model b+
Please help fix this problem thank you.

[rpdom]

Can you post a link to the type of relay board you've got?

It sounds like you have one that uses an inverted input, so setting the line Low turns the relay on. If you have, then that should be easy to get around by changing the program logic so it sets the pin low when it wants to turn something on.

[ikequan]

Thank you rpdom for your quick reply
this is the link to the relay am using: http://www.aliexpress.com/item/2pcs-lot ... 92610.html

this is my python code:

#!/usr/bin/env python

#pretty obvious, but you'll want these dependencies to be installed for this script to work
import RPi.GPIO as GPIO, time, requests, os

def cls():
os.system(['clear','cls'][os.name == 'nt'])

DEBUG = 1

RED = 23
GREEN = 24
BLUE = 25

GPIO.setmode(GPIO.BCM)
GPIO.setup(RED, GPIO.OUT)
GPIO.setup(GREEN, GPIO.OUT)
GPIO.setup(BLUE, GPIO.OUT)

response = requests.get('http://YourWebsite.com/test.php')

while response.text != 'exit':
response = requests.get('http://YourWebsite.com/test.php')

colrs = response.text
r = colrs[0]
g = colrs[1]
b = colrs[2]

cls()

if response.text == 'exit':
print (colrs)
else:
print ("R" + r + ", "),
print ("G" + g + ", "),
print ("B" + b)
print

if r == '1':
GPIO.output(RED,True)
else:
GPIO.output(RED,False)
if g == '1':
GPIO.output(GREEN,True)
else:
GPIO.output(GREEN,False)
if b == '1':
GPIO.output(BLUE,True)
else:
GPIO.output(BLUE,False)

#time.sleep(0.25) #uncomment this if you want the polling loop to be slower

[DirkS]

this is my python code:

Indentation is important in Python.
Please use a

Code: Select all

[/b] block when posting code

[DougieLawson]

I followed some steps online to setup my raspberry pi and relay but when i set the GPIO(pin 7) to high(true) the replay turns off and when the GPIO is set to low(false) the replay turn on.

That's 100% normal for the cheap relay boards from China. You just have to turn your logic upside down.

Use this

Code: Select all

import RPi.GPIO as GPIO
.... # same stuff as you've got # ...

# reverse logic values because relays work backwards
ON=False
OFF=True
GPIO.output(BLUE, ON)
GPIO.output(BLUE, OFF)

[ikequan]

@DougieLawson thank you for the reply..

I reversed the logic of the python code and seems well but i think there is some problem with the relay still...even when the Raspberry Pi is turned off and the bulb connected relay is still plugged to the wall, the bulb seems to be on i.e. the relay is still closed when off and opened when on.

Please can anyone help me with this?

[SpazzTechTom]

@DougieLawson thank you for the reply..

I reversed the logic of the python code and seems well but i think there is some problem with the relay still...even when the Raspberry Pi is turned off and the bulb connected relay is still plugged to the wall, the bulb seems to be on i.e. the relay is still closed when off and opened when on.

Please can anyone help me with this?

Some relays are normally open and some relays are normally closed. Some relays are both. It sounds like you may have a normally closed type relay which means when there is no current flowing through the control coil, the relay is closed, and the light is on. When current flows through the control coil, it opens, and the light turns off. From the link you gave I did not see a datasheet for the relays. If you have a datasheet, you should be able to tell for sure.

[ame]

@DougieLawson thank you for the reply..

I reversed the logic of the python code and seems well but i think there is some problem with the relay still...even when the Raspberry Pi is turned off and the bulb connected relay is still plugged to the wall, the bulb seems to be on i.e. the relay is still closed when off and opened when on.

Please can anyone help me with this?

On the board you linked to it seems that each relay has three screw terminals. I expect these are 'C','N/O' and 'N/C', i.e. Common, Normally Open and Normally Closed, although they might not be labelled like that. I also think you are using 'C' and 'N/C'. Try the other terminal (using 'C' and 'N/O').

[klricks]

@DougieLawson thank you for the reply..

I reversed the logic of the python code and seems well but i think there is some problem with the relay still...even when the Raspberry Pi is turned off and the bulb connected relay is still plugged to the wall, the bulb seems to be on i.e. the relay is still closed when off and opened when on.

Please can anyone help me with this?

A relay usually has 3 contacts Normally Open NO, Normally Closed, NC and Common.
If you use NO and common then when the relay is off (not energized) the contacts are open (OFF).
If you use NC and common then you will get the opposite. The contacts are closed (ON) when the relay is off. This condition is also true if the relay board is not powered at all. The external circuit will be on.
So you probably want to use the NO and common terminals.

[ame]

Is there an echo in here?