Hey.

How complicated would a 5 led chaser be to design? Id want it to go back and forth rather than run through the leds and "start from beginning"?

I just beginning electronics and digital tech so i dont want to start with too daunting a task. what would be the absolutely essential theoretical aspects to cover for completing such a design? Im planning to design it on logisim for now and see how things work.

 

Try our resident expert's article - http://forum.allaboutcircuits.com/showthread.php?t=19075

 

The article beenthere pointed to is a work in progress, I'll be updating it now and again. You want to see a neat variation of this concept check this thread out...

http://forum.allaboutcircuits.com/showthread.php?t=26977

For your project a 555 and 4017 chip is needed, along with a handful of diodes (general purpose, exact P/N unimportant), resistors, transistors, and LEDs. If you have any specific questions feel free to ask.

 

Use the 4017 as a ring counter,use diodes to make 5 OR gates- output to directly drive 5 lo current LED's, or buffer amp. Connect stages 0 & 9, 1 & 8, 2 & 7, 3 & 6, 4 & 5.Disadvantage- end LED's stay on for 2 cycles

 

Make the counter drive the LEDs when it counts from 1 to 5 then make the 6th output light the 4th LED through a diode, the 7th output lights the 3rd LED through a diode, the 8th output light the 2nd LED through a diode and the 9th output resets the counter so it can start with the 1st output lighting the 1st LED again.

 

This is basically what Audioguru's talking about:

For this schematic, you'll need to use a diode on any 4017 output that powers an LED, if only to keep the voltage drop consistent; thus the light from the LEDs consistent. You could use 1N4148/1N914 or 1N400x series diodes.

The value of R3 will need to be adjusted depending upon your supply voltage and LEDs.
A rough calculation is:
R3 >= (Vsupply - (Vf(LED) + 0.7v)) / 12mA (the 0.7v is the approximate Vf of the diodes)
So, if you were using a 12v supply and LEDs that had a Vf of 2.2v:
R3 >= (12v - (2.2v+0.7v))/12mA
R3 >= (12v - 2.9v)/0.012
R3 >= 9.1 / 0.012
R3 >= 758
A table of standard resistance values is here: http://www.logwell.com/tech/components/resistor_values.html
758 is not a standard E24 (green columns) value. However, 758 Ohms is so close to 750 (99%) that I'd just use 750 Ohms.

I used CD4093 NAND gates wired as a bistable multivibrator. You could use a CMOS 555 timer instead if you wished.

Note that any unused CMOS inputs must be wired to something; whether Vdd, ground or a signal that stays between the power rails. Otherwise, you will have problems.