Adding lots of LED's together

I was just wondering how you are able to get more LED's than pins to work on the Arduino Uno without scrolling through thousands of topics?

Cheers

mitchK:
I was just wondering how you are able to get more LED's than pins to work on the Arduino Uno without scrolling through thousands of topics?

Dunno.

Depends what you actually mean by "more LED's than pins".

It also depends on exactly what you mean by to work , is that fade up and down or switch on and off?

switch on and off and how to multiplex

mitchK:
switch on and off and how to multiplex

You're going to have to be a bit more forthcoming about what you want to do, otherwise the answers are going to be equally short!

Do you want to learn how multiplexing works, or use it without having to know?

If the latter, use max7219 chips. They drive 64 leds each and you can add as many of them as you like (well, up to a point) to an Uno and still only use 3 Uno pins.

Paul

Or maybe you need more LEDs than you could fit in a matrix, in which case WS2812 or other individually addressable LEDs would be appropriate. These let you control hundreds of LEDs with one pin - but the refresh rate is limited (depending on the number of LEDs). Or you could use shift registers if for some reason that made more sense for your application. There are all sorts of ways to do this, depending on what your needs are.

Have a look for "charlieplex" in the Playground

JimboZA:
Have a look for "charlieplex" in the Playground

Considering he clearly doesn't even know what he wants in the first place, that is going to be right confusing! :astonished:

I was just wondering how it works!

mitchK:
I was just wondering how it works!

OK. In one sentence: by Multiplexing fast enough to achieve Persistence Of Vision.

Multiplexing means that not all the leds are lit at any instant in time. Only one group is lit and all the other groups are off. Then the first group goes off and a second group lights, and so on, until all the groups have had their turn. Do this fast enough, and the human eye thinks they are all on at once, because of Persistence of Vision.

http://www.adafruit.com/product/274