View Full Version : new to stamp want to control 25 leds

11-06-2009, 01:40 AM
I am new to stamp I want to control 25 led to turn off and on with 25 mom switch. I would like to know if stamp is the right ic to use

Mike Green
11-06-2009, 01:56 AM
A Stamp is perfectly capable of controlling 25 LEDs and sensing the state of 25 switches. It can't do it directly by itself because it has only 16 I/O pins, but it can do what's called multiplexing which means that the LEDs and switches are connected in a 5 x 5 matrix and the Stamp works with 5 LEDs and 5 switches at a time and cycles rapidly through each set of 5 to handle the whole thing while using only 15 I/O pins.

Nuts and Volts Column #22 shows how to handle a 4 x 4 keypad when only one button would be pressed at a time. The circuitry and coding would be more complicated if you wanted to allow more than one button to be pressed at a time, but this is one example of how a button matrix might be handled.

www.parallax.com/Portals/0/Downloads/docs/cols/nv/vol1/col/nv22.pdf (http://www.parallax.com/Portals/0/Downloads/docs/cols/nv/vol1/col/nv22.pdf)

Post Edited (Mike Green) : 11/5/2009 6:03:45 PM GMT