I've build a Clock using a 5cm high 5x7 Dot Matrix Display. The problem is that the LED's do not shine enough. So i thought to put a lower resistor into the circuit. First i used a 330 Ohm resisitor (about 10mA) and the i put a 150 Ohm (about 20mA). The confusing thing is, that the led's with 150 Ohm don't shine much brighter than the others with 330 Ohm. So it has to have something todo with my update routine. I played around with the timing values and could improve the bightness a little bit, but there should be more to get out of this display. Any ideas or any knowledge about this problem?