I'm trying to build a 10x10 LED matrix using high brightness LEDs. I understand that these LEDs cannot be powered directly off the microcontroller, so I reckon I need to use transistors to do the job. I came up with the following, but I'm not sure that it's right? I'm not great with transistors, so any help would be appreciated. Also, what specific transistors should I purchase to do the job? I'll be using the microcontroller to go through each pixel on the grid one by one, so the resistor will only need to account for the load of one LED at a time, is this a correct assumption to make?
Your 1k resistor is in the wrong place and limits the LED current to only 2mA which is very dim if it is continuously lighted and is way too dim if it is multiplexed.
The input to the PNP transistor cannot go to ground because its emitter is no lower than 2.1V. Its base current must be limited.
SOMETHING IS WRONG WITH THIS WEBSITE BECAUSE I CAN'T ATTACH A SCHEMATIC.
A transistor is a switch when its load is at its collector, not at its emitter. You are throwing away 10V and making it complicated to drive the PNP transistor since the supply voltage is too high. If the supply voltage for the LED matix is the same as for the micro-controller then it is simple like this:
Driving an LED Matrix
Posted - Nov 23 2010 : 12:45:23 PM
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