I started by playing with the delay time so the lights would blink faster. The example code has a delay set to 1000 so I tried 300, 100, then finally 10. The lights were blinking extremely fast and then they didn't blink anymore :-[
Did I simply burn out the chip? What caused it? Is there a limit to how fast the 74HC595 can be clocked or something? I'm a complete newbie to this stuff so forgive me if these are dumb questions.
To clarify I put a new 74HC595 in and it works fine again so I obviously did something to the chip. I just am wondering what the limitations are since I want to hook up a pot that will give a variable rate control to the blinking lights but of course I want to avoid burning out another IC. I'm working toward building some sort of sequencer with a variable clock so I guess I will need to determine the upper limits of the possible clock rate and prevent it from going higher. Thanks in advance.
that's what I was going to ask... I run an LED matrix using two 595s and no delay at all (I really don't like using delay) so they're receiving bytes from arduino as fast as the little guy can throw them out. also, are you powering the 595 right off the 5v of the arduino?
Oh man, I made a really stupid error. I failed to notice that the resistors in the diagram were crossing the gap on the breadboard. So I had the LED and both pins of the resistor all on one row together. But why did this burn out the chip rather than the LEDs?
if the resistors were shorted, then the chip tried to drive as much current as it had available into the LED's 2V load.
The actual transistors inside the 595 that do that for you are tiny... source too much current, and it's gone.