I need help making a LED chaser with about 20 -30 LEDs with a 555 timer and i would also like to be able to change the speed of how fast the LEDs would flash. Thanks.

 

if you use the search at the top of this page
and type in chaser , you get a lot of responses.

 

The 4017 CMOS is your friend. 8) I'll post a wiring diagram of my insane 100 LED chaser if i can find the file.

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www.winpicprog.co.uk - Great PIC language tutorials.

 

Wow. 100 LED chaser? that must be amazing... Throw it in a computer, insane modding capability...

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-Ian

 

depends what you want....
as far as my taste goes 3..5 channel is the best.
so all you need is 555 and 4017 wired to count to 4 or 5.
on each channel attach string of 3-4 LEDs and tie all strings
to one resistor to ground (number of LEDs will depend on voltage
you use and Vf of the LEDs). done...
some 15-20 LEDs are no problem without additional circuitry...
if you need more LEDs, add transistors to each used 4017 output
so you get more current. then you can add multiples of strings
per channel...
changing frequency of the 555 will control chasing speed (you can make it reaaaaal slow or just as insane fast as you can still see it....)
next step is your own homemade version of jumbotron :-)