LED Chaser Help

[Connorrsell]

Looking to make a 4 LED chaser with a 555 timer but I don't have access to a 4017 decade counter today and I need it for tomorrow morning. A Halloween costume lol. I would like to build it using a 74ls95 shift register but need a little help on the operation part of things. New member here and it looks like just the right place. Thanks!

 

[Colin Mitchell]

5 LED Chaser

 

[Gryd3]

What other components do you have on hand/access to?
The 74ls95 will work splendid if you can manage to load an initial value into it to be able to shift. Once you can do that, I'm certain you can tie one of the outputs to the serial input to make it loop.

Edit: Not bad Colin, uses readily available components and can be scaled up or down. (That's what I get for writing my post and walking away before hitting submit

 

[(*steve*)]

A 4017 and a 555 is also a solution.

Even if you use the 74LS95 you will need a clock source.

The issue with the 74LS95 is that you want to load just a single bit into it and allow it to circulate.

Connecting Q1 to P0, Q2 to P1, Q3 to P2, and Q0 to P3 will allow the "load" function to rotate the bits. That also doesn't give you a way to inject a single "1".

If you place an inverter in just one of these links (say the Q0 to P3 link) then the pattern will become:

0000
0001
0011
0111
1111
1110
1100
1000
and back to 0000

All this requires is a reset on power on.

If you also use a 74LS14, you have 6 Schmitt trigger inverters. One can be used to make an oscillator (I'm not sure how well this works with LSTTL), one can be the inverter you need, and the other 4 can buffer your outputs Q0 to Q3 to allow you to drive LEDs without affecting the logic levels. The reset can probably be done with an RC delay.