5v Relay will not close (unless using GPIO cleanup)

Question

This seems like it should be really simple, so maybe I am missing something. I am just trying to open and close my relay but all it does it open's and doesnt close. I can use GPIO.cleanup() to make it close but I dont want to apply this at this point in the project.

Link to 5v relay -> https://www.amazon.co.uk/XCSOURCE-Channel-optocoupler-Arduino-TE213/dp/B00ZR3B252

UPDATE: 6th Jan 17 As suggested in the comments I have tested the GPIO's and can see that 3.3V comes out when HIGH and it goes back to 0v on LOW. But LOW does not turn off the relay oddly. I have tried 2 of these relays and both do not switch off when at LOW (0v).

I have tried to find the original documentation for GPIO.clean() function since this allows it to close but cant find it. Can anyone think why this does this?

import RPi.GPIO as GPIO
from time import sleep

relayPin = 32

GPIO.setmode(GPIO.BOARD)
GPIO.setup(relayPin, GPIO.OUT)

## Turn on the Relay (this works - it clicks gives 3.3v)
GPIO.output(relayPin,GPIO.HIGH)
sleep(1)

## Turn off the Relay (this does nothing but goes back to 0v)
GPIO.output(relayPin,GPIO.LOW)
sleep(1)

## if I add GPIO.cleanup(), the relay then closes, 
## but I dont want to cleanup at this point

Answer 1

I had the same problem as you, but I finally solved it.

As you are powering it with 5V, both 0V or 3.3V coming from the GPIO pin are considered as "low level", so it won't actually switch.

You need to power it with 3.3V (it seems it was designed to work also with lower voltages), this way it can correctly distinguish between 0V (low level) and 3.3V (high level).

Answer 2

You can't use 5 V relay with signal from Raspberry Pi while Raspberry Pi signal is 3.3 V. So if you used Logic level converter to convert 3.3 V from Raspberry to 5 V then to relay in I think it may solve this issue.

I don't know why most distributors say it should work with raspberry pi while the ideal one for Raspberry Pi is 3.3 V relay.

So you have 2 choices either:

1. 3.3 V relay, or;
2. Logic level converter with a 5 V relay.

Answer 3

The specs for this relay state that the trigger is "● IN: relay module trigger pin (high level trigger) ● Trigger voltage:2-5V", which means that it should turn ON with a GPIO.HIGH command (+3.3V) and turn OFF with a GPIO.LOW command (0V or ground).

Can you check the voltage output of the PRi's GPIO pin when it is set to HIGH to make sure you are getting the full +3.3V? It's possible that you are not reaching the trigger threshold.