Random 8+ LED Flasher

T

Tim Williams

Jan 1, 1970
0
Nah, you can get by with half that, just add glue logic (AND, OR, XOR, etc.
combinations) to make different patterns.

I've made some "Blinkenlites" using a 74LS168(?) serial-in, parallel-out, 8
bit shift register and a quad XOR gate, wired as a pseudorandom number
generator. The light pattern cascades to the right, but that isn't as
noticable when you spread them out and break up the movement. There are 255
combinations, so it's got a pretty long repeat for being two chips and a
clock (555, let's say ;).

Tim
 
D

D from BC

Jan 1, 1970
0
Nah, you can get by with half that, just add glue logic (AND, OR, XOR, etc.
combinations) to make different patterns.

I've made some "Blinkenlites" using a 74LS168(?) serial-in, parallel-out, 8
bit shift register and a quad XOR gate, wired as a pseudorandom number
generator. The light pattern cascades to the right, but that isn't as
noticable when you spread them out and break up the movement. There are 255
combinations, so it's got a pretty long repeat for being two chips and a
clock (555, let's say ;).

Tim

I'm familiar with that technique. (MLS generator...maximum length
sequence)
Basically an out of order binary counter.
I read an article years ago about someone who wrote a computer program
just to "search" for logic tapping locations for various register
lengths to produce all combinations. Improper logic results in not
producing all combinations (a shorter sequence).
The program had a long run time. I guess he wasn't able to do the math
which I think was so intense that it was quicker to run a "hit and
miss" type program.
D from BC
 
M

Mike Silva

Jan 1, 1970
0
Or a micro (circuit easy, coding required)

And best of all, highly modifiable. And this application sound like
one that will take many iterations to get the desired random flashing
effect. Much easier to do that in code.
 
R

Rich Grise

Jan 1, 1970
0
I'm familiar with that technique. (MLS generator...maximum length
sequence)
Basically an out of order binary counter. I read an article years ago
about someone who wrote a computer program just to "search" for logic
tapping locations for various register lengths to produce all
combinations. Improper logic results in not producing all combinations (a
shorter sequence). The program had a long run time. I guess he wasn't able
to do the math which I think was so intense that it was quicker to run a
"hit and miss" type program.

Don Lancaster has circuits up to, I think, 31 bits in his TTL cookbook - I
wonder if he's posted any of them on line?

Don? Are they on your site somewhere? If not, would you put them up? (I
lost track of the cookbook several moves ago )-; )

Thanks,
Rich
 
D

D from BC

Jan 1, 1970
0
Don Lancaster has circuits up to, I think, 31 bits in his TTL cookbook - I
wonder if he's posted any of them on line?

Don? Are they on your site somewhere? If not, would you put them up? (I
lost track of the cookbook several moves ago )-; )

Thanks,
Rich

How's he supposed to make book sales if he's posting the goods on here
:p
I have his Active Filter Cookbook I bought around 1989...One of my
favorite books..
He shouldn't be allowed to get old. :)
D from BC
 
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