How do I connect to a 4-Channel relay? Plz help! :D

Hello everyone!

I'm very new to Arduino, but I'd like to think I learn quickly.

I apologize if this question has been answered 1000's of times in different ways. But I still have questions about controlling relays through the Arduino UNO.

Below is the kind of relay I'd like to buy:

The VCC, CH1, CH2, CH3, CH4, and GND connectors seem pretty straight forward.
VCC = 5v on the Arduino, GND = GND on Arduino, and CH1-4 = any digital connection on Arduino.

But I have no idea what to connect to the NO, "/", and NC connections on the relay board...

Below is a picture from a Sparkfun Tutorial: Controllable Power Outlet - SparkFun Electronics. Which is based off of this product: Relay Control PCB - COM-09096 - SparkFun Electronics

The image above shows a single relay. The black cable is spit, going first into "Normally Open" and then out of "LOAD" spots on the board.

I'm going to guess that "Normally Open" = NO on the relay board I want to buy.

Could someone please explain how I would connect the Green, White, and Black cables in this example to the 4-channel relay board I would like to get?

Can anyone tell if I need to add a Transistor, Diode or any other components to a relay board like the one I want to buy?


EDIT: May have answered my own question... NO=Normally Open, NC=Normally Closed, and the "/" is Common? I guess the Sparkfun explample did not have a Normally Closed option. I think this is enough info to go ahead and buy the board, but does anyone know if I need a transistor or diode?

You don't need a transistor or diode, they are already included on the relay board. Connect the Vcc pin to Arduino +5v, the Gnd pin to Arduino ground, and the Ch1 to Ch4 pins to Arduino digital outputs.

Indeed - there is a schematic but only on the page for the 2-channel version of the relay board. The inputs are logic level (and probably work at 3V3 too), the Vcc is the +5V supply for the relay coils (20mA per coil). Simple to interface so long as you can provide the 80mA at 5V.

Thanks everyone!

Hi, Information on similar relays here: (scroll down for the schematic)

And a similar relay, but with optical isolation:

General information on Arduino Power, relays etc:

A wider variety of relays:

DISCLAIMER: Mentioned stuff from my own shop...!

Thanks terryking that is great info. The schematics are very useful.