Help me about 8x8 Matrix led

[Nhan95]

I buy an one color 8x8 matrix led. But It has 24pins !! I think it ought to have only 16 pins. So I'm confused how to use it. Could you help me ?

[Thor-Arne]

First, we need to see the datasheet.
Post the brand and part number.

I expect this to be a dual-color matrix.

[mikeselectricstuff]

Probably dual colour, though you sometimes get single colour ones in a dual-colour package where they have only populated one set of colour die.

[JoeN]

On most devices I would say you need a datasheet too, but not for an LED matrix, at least not for hobby purposes.  If your intent is to build commercial devices, you need the datasheet, though.  This is just for playing around with.  LEDs are the easiest things to "buzz out" in the world.  The way I do it is send 5V to my breadboard, put a sane resistor like 330 ohm between 5V and another point, add a long test lead to that point, a long test lead to ground, plug the matrix in, and just try random connections until I get a segment to light up.  Under these conditions, that is safe.  Once you find a connection through an LED note your lead positions then move the ground lead to find another good position.  If the row moves then it is row common cathode and if the column moves then it is column common cathode.  Either way, check all positions with the GND lead to find all of the columns or rows and then repeat with the VCC lead to find the other. 

Like this, which only took me a few minutes to do: