Pololu item #: 2480


I have the basic SPDT relay Carrier with 5VDC Relay, and am trying to activate it with Raspberry Pi 3 B+ GPIO pins.
Reference: http://301o583r8shhildde3s0vcnh.wpengine.netdna-cdn.com/wp-content/uploads/2015/04/Raspberry-Pi-GPIO-compressed.jpg

I have the GND connected to pin 9, which is ground.
I have tried connecting VD0 to pin 1 which is 3v, and pin2 which is 5v.
I have EN connected to pin 3.

The Raspberry pi’s GPIO pins output about 2.8v, I have confirmed this with a multimeter. This does not activate the relay, wether using 3v or 5v connected to EN.

When I connect VD0 and EN to the positive side of a 9v battery, and GND to the negative side, the relay activates fine.

What am I doing wrong here? Is there another relay I should be using?


Hello, Wayne.

Can you post some pictures of your setup and tell me how you are controlling the Raspberry Pi pin connected to EN? If you are using a script, can you post it? Can you confirm that you are driving the pin high and not just enabling a pull-up?

By the way, VDD (not VD0) should be supplied with 5V since it is a 5V relay.

- Patrick


This is how I’m controlling the pin:

import RPi.GPIO as GPIO

GPIO.setmode(GPIO.BCM)  # Set to BCM
#GPIO.setmode(GPIO.BOARD) # Set to board

GPIO.setup(2, GPIO.OUT)
#GPIO.output(2, 0)
GPIO.output(2, 1)


The script is rough right now, as I’m just trying to get the circuitry to work at this point.

The cleanup function resets any GPIO you used to an input, so I think you need to add some delay between setting GPIO pin 2 high and calling the cleanup function so that the relay actually has time to activate and so that you have time to observe it.

Also, in your picture it looks like you have VDD supplied from a Raspberry Pi 3.3V output, not a 5V output, so please make sure you fix that.

By the way, unless you have some other reason to prefer an external image host, it is probably easier and works better to upload images to the forum directly.

- Patrick

Hello Patrick, thank you for your replies. I’ve moved the VDD to the 5v output, and I’ve added a sleep function before cleanup. I can observe with a multimeter that the pins are now staying high, but the relay is not activating. These GPIO pins do not output 5v and I’m afraid that’s the problem here.

I’m thinking about a MOSFET that can simply turn true OFF / true ON with low voltage signals like what the Pi’s GPIO pins produce. I’m looking at this

The GPIO pins not being 5V should not be the problem here. While VDD does need to be 5V, EN can be a low as 2.5V as we state on the product page. Can you post some updated pictures of your setup along with some pictures that show the bottom of the relay board so we can see the solder joints?

The RC switch you linked to has a completely different type of input interface that was designed to work with hobby RC signals, not digital on/off signals, so I would not recommend that for an application where you will be controlling it from a Raspberry Pi.

- Patrick