I want to use an Arduino to make a bunch of LEDs "chase each other". You usually see this "chase" pattern with Christmas lights that are hung on the outside of houses. The lights seem to chase each other around the string of lights. I don't know how to do this with a microcontroller- it seems like you would need as many output lines as you have lights (which may be inthe 100's), but I'm sure this isn't the case.
Does anyone have any ideas?
Thanks
These chasers appear to me to be just a few "pixels" wide, like 4 or 5. The whole train is just those few repeating. This would mean you'd only need 4 or 5 outputs, but need plenty of current to drive them.
-j
"just a few "pixels" wide, like 4 or 5. "
What do you mean by pixels?
I'm referring to the lights that hang outside a house- at the edge of a roof
4 or 5 sets of lights then?
having a 100 christmas lights and lighting only one of them doesn't seem that bright or interesting 
most people know a pixel to be a single controllable element. Now do you get it?
if not, maybe this well help. On a standard "running" light string, every 3rd pixel/bulb/LED is connected. And that means that the 1st bulb is connected to the 4th, the 2nd connected to the 5th, the 3rd connected to the 6th, as if there were 3 sets of lights combined into one string. Light string one for 1sec, turn it off, light string 2 for 1sec, turn it off, light string 3 for 1sec, turn it off, repeat.
if you don't believe this, do it in a graphics package like Gimp and save it as an animation.
4 or 5 sets of lights then?
having a 100 christmas lights and lighting only one of them doesn't seem that bright or interesting
That wouldn't be. I'm talking about 50 sets of 5, not 5 sets of 50. See the difference?
Let's say you have 4 "pixels" (pixel - picture element; think of your string of lights as a picture 1 pixel high and many many long) and 100 lights in the string. They would be wired and controlled like this:
1-2-3-4-1-2-3-4-1-2-3-4-1-2-3-4-1-2-3-4-1-2-3-4-1-2-3-4-1-2-3-4-1-2-3-4-1-2-3-4-1-2-3-4-1-2-3-4.....
So, there would be 5 wires: power for the 25 lights on 1, 2, 3, and 4, and a common ground. You would need 4 driver circuits capable of driving 25 lights each.
then:
turn on pixels 2,3 and 4.
pause.
begin loop:
turn on 1, turn off 2.
pause.
turn on 2, turn off 3.
pause.
turn on 3, turn off 4.
pause.
turn on 4, turn off 1.
pause.
repeat forever.
-j
having a 100 christmas lights and lighting only one of them doesn't >>seem that bright or interesting
Who said anything about only "one light" ?
1-2-3-4-1-2-3-4-1-2-3-4-1-2-3-4-1-2-3-4-1-2-3-4-1-2-3-4-1-2-3-4-1-2-3-4-1-2-3-4-
1-2-3-4-1-2-3-4....
Ok - I'll try this on a smaller scale.
Thanks