Hooking up Relay Board

Hi All,

I'm a bit confused... Does the Arduino put out enough current to drive this relay? If not where am I supposed to get 5VDC?

Thank you,
Scott

beefey:
Hi All,

I'm a bit confused... Does the Arduino put out enough current to drive this relay? If not where am I supposed to get 5VDC?

No, if you try to pull the power for a relay through the Arduino you'll fry it. You need a ACDC power pack, or some batteries, or any other source of 5V to drive your relay and a transistor to switch it from the Arduino.

If this question was about some specific relay or relay module then you should probably mention which one and provide a link to it.

It is my understanding the package has a transistor integrated?

Yes, and the relay coil draws only ~80mA from the 5volt pin and a few mA from the signal pin.
Not a problem to power/control a single 5volt relay module from an Arduino.

I think this relay module should only be used for low voltage applications (not mains power).
Leo..

In this tutorial hes driving 4 relays with the 5VDC bus right?

http://www.hobbyist.co.nz/?q=interfacing-relay-modules-to-arduino

I'm only putting 1A @ 12VDC through the relay.

Relay coils only draw current when active.
Four relays (4*80mA and ~50mA for the Arduino) is getting close to the limit (500mA) the 5volt pin can supply on USB power.
Not much left if you also want to use sensors.

A 12volt/1Amp load could also be switched with a logic level mosfet, or NPN darlington.
Depending on the load, and if grounds can be shared.
A mosfet switch doesn't draw any current (from the Arduino pin).
A TIP120 with 1k base resistor draws less than 4mA.
Leo..