[lao3x]

I already know how to make LED's blink but only all at once.
What is the easiest way to make 3 LED's (red yellow green ) blink one at a time?

 

[audioguru2]

A CD4017 is a Cmos sequencer IC. It has 10 outputs that go high one at a time one after the other. The outputs can be connected to an LED through diodes so that the red and green lights turn on for a longer time than the yellow.
Outputs 1 to 4 have diodes and turn on the green LED for a long time.
Output 5 turns on the yellow LED for a short time.
Outputs 6 to 9 turn on the red LED for a long time.
The 10th output is not used.
The CD4017 needs to have an oscillator that can be made with a 555 or C555 timer.
Use 6V to 9V to power the circuit.

 

[Hero999]

What sort of sequence do you wand?

Red, yellow then green?
Or:
Red, red + yellow, green, yellow, green?

I can think of a simple way of doing it using the LM339, the CD4017 will also work.

The comparator idea has the advantage of using less active parts but needs more passives and is only limited to red, yellow and green.

The CMOS idea requires two ICs but has the advantages of being able to do either sequence and requires less passives.

 

[lao3x]

Would this work?
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=296-14094-2-ND

Or if you guys know where to buy it in the US tell me.

 

[audioguru2]

Yes, you found the CD4017 IC at Digikey.
But it is in an extremely small "surface-mount" case that is so small that it is difficult to solder unless you know how.
Digikey delivers parts in the US and Canada the next morning if you order before 8:00PM the day before.

 

[sparky3489]

This is about as simple as it gets for a real traffic light if that's what you're after.

View attachment 40560