Powering 20x RGB LEDs

[LimeBlast]

Hi all, I'm pretty new to electronics, so please excuse any stupid questions

I'm working on a project which uses the RGB LEDs sold by Hobby Components, 20 of them specifically. I'm going to control them using an Arduino, and have in fact been semi successful making 5 of them work, powered directly from the Arduino itself.

But having read the documentation, I know that if I want to use more than 5, I need to use an external power supply - so this is my question to you, what power supply should I be using?

Ideally I only want one wire coming out of my project, so whatever it is should be able to power both the LEDs and the Arduino.

As mentioned, I'm totally new to this, so any advice you can give will be welcome. Thanks.

[andrew]

Most Arduinos can be powered directly from a 5V source. Which Arduino board are you using?

[LimeBlast]

I'm using an Uno.

It's more the LEDs I'm concerned about - if I can power 5 of them directly from the arduino, excellent - but I need to power 20 of them, and I don't know how.

Thanks.

[andrew]

The amount of current each LED draws is dependent on both its colour and brightness. With the colour of each LED set to white and maximum brightness, each LED will draw ~60mA. With 20 LEDs that would be a total of 1.2A which is too much for the 5V regulator on the Uno so you will need an external 5V power supply. I'd recommend a 5V adapter that can supply at least 1.5A.

You should also be able to power your Uno from the same 5V supply by connecting the supply to one of the 5V pins on the Uno. This will bypass the Uno's 5V regulator and power the Uno directly. So:

5V PSU + ----> LED strip +5V pin
5V PSU - ----> LED strip GND pin

5V PSU + ----> Uno +5V pin
5V PSU - ----> Uno GND pin

Uno D8 pin ----> LED strip DI pin


Hope this makes sense.

[LimeBlast]

Yes I think so, thank you.

So something like this should be able to do it?

I'm not sure how I'd take the power from the adaptor into the pins/LEDs, but I guess I can cross that bridge when I get to it.

[andrew]

Yes that will work. In fact that PSU also comes with a USB socket adapter so you can just simply connect it to your Arduino using a standard USB cable as you would to a PC. Supplying 5V to the Uno via it's USB socket also bypasses the Unos on-board 5V regulator so it will be safe to power the Uno and the LEDs in this way. Just make sure you set the adapter to 5V before connecting it to your Uno.

Another possibility I should point out is that if you're powering it from a PC with a USB3.0 port, a lot of USB 3 ports have a high power charging mode and can supply 1.5 amps rather than the normal 0.5A of a standard port.