How to use 12VDC Relay Module with Arduino

[ronnyrobertson]

Thanks mate, it was very difficult to find the answers to my questions about 12v relay modules and arduino, but this video had the solutions :)

[-ColorMehJewish-]

This has been the best explanation and tutorial I have seen in many days of searching...
But I am running into a problem.
When I connect my setup like this (I am using a WEMOS D1 R2 (looks like the Arduino Uno style board), and I seem to only be able to turn off my relay if I manually move the data pin from D2 which I was trying to use, to a ground on the board.

I have everything else in the wiring setup like you have, but I am using a S8050 D-331 NPN transistor instead (its what I had on-hand).
If I touch the D2 pin's wire (coming from the D1 board) to the base of the S8050 D-331, and the data IN on the 12V relay (same exact look as what u have -- I compared #'s on top), my 12V relay switches to the ON position. If I touch both the D2 pin (my chosen data pin) and the IN on the 12V relay together, the relay switches also.

So I think I might need the other type of transistor, as the bottom of my relay says "Low Level Trigger". I suspect that's why it works when I connect it to ground pins.
I am having so much trouble finding out what I am doing wrong, as I have been trying this 12V model relay and I have tried 5V models w/o success. I just tried the 5V relay (does not say low level trigger) and it does not seem to react whatsoever, unless once again I just take the data pin and connect it straight to a ground.

Getting a damn relay to work should not be more difficult that programming the code that it's going to use, and yet it's much more difficult to fig out.
I have built CO2 sensors and temp sensors that utilize MQTT and WiFi... yet I cant get a stupid relay working. It's so beat.

[Teknisi_otak_atik]

really helpful dude, i try so many times with relay 12V cannot work normally

[md.emranhossain]

the transistor solution help me to solving my relay issue, thank you

[kezif]

I wondered why my 12v relay doesnt work with arudino. Thanks for the explanation

[ilham]

thanks a lot, its give me answer after i destroyed 1 esp due to short circuit 😩

[setoku]

I also use an Arduino Uno and a 12V relay module. And for some reasons, I can still control the relay module without a transistor 😅

[MeanderingMonkey]

Hi passion, why is the collector pin not connected to anything? I thought you need voltage from collector pin to generate current from collector to emitter.

[adityavenkateshwaran]

This is a nice video.
I had a doubt, what exactly is the NPN transistor doing so that the solenoid is 5 seconds ON and 5 seconds OFF?

[majdizamiti]

It work thanks, but i use a module 4 relay 12v and the transistor make all the relay become one relay

[juliusferrer]

Whats the specific model of BC547 you use?...i tried BC547 B 080..it wont work

[DodoTheCreator]

But some relay modules have transistors on the board, or doesnt yours have because on my board i can see a j3y transistor SMD

[joescopo]

If I used a 5v relay instead of the 12v relay, I wouldn't need a transistor, right?

[oliveradriel]

Would the circuit be the same if you use a 24v power source and a 24v relay?

[m.fadhiilhaekal]

I use 2n2222, i connect the data to emmiter and collector to in, and it works strangely 🤣

[prajeetbohara]

I’m trying to do it on a raspberry pi 4. What do you suggest? Can I have the code and circuit diagram of the project that you have done ?

[arindumroy]

Its not working with esp boards. Its always low in the esp board no matter what you do. Can you explain whats the problem

[hemahema]

i have a question why we used a transistor what is he role of this transistor in this case

[pavankumarnarala]

I have arduino uno r3, 12v relay module and 12v dc water pump, and 12v dc supply but the pump is not running

[majdizamiti]

I have the same problem with NODEMCU ESP8266 and i try your solution but not working😟