4017 Counter LEDs to stay on

hp1729

Joined Nov 23, 2015
2,304
Hello All About Circuits forum,

Using an Arduino to control a dozen 4017 - 555 circuits to sequence
320 LEDs. The problem is the 4017 turns on LED 1 then turns it off
and then turns on LED 2. The project wants to turn on LED 1 and
leave it on and then turn on LED 2 and leave LED 2 on, then
turn on LED 3 etc.

Maybe the 4017 won't do this but does any one know if it will
and if so how?

Thanks.

Allen in Dallas
Hello All About Circuits forum,

Using an Arduino to control a dozen 4017 - 555 circuits to sequence
320 LEDs. The problem is the 4017 turns on LED 1 then turns it off
and then turns on LED 2. The project wants to turn on LED 1 and
leave it on and then turn on LED 2 and leave LED 2 on, then
turn on LED 3 etc.

Maybe the 4017 won't do this but does any one know if it will
and if so how?

Thanks.

Allen in Dallas
Shift register (74xx595 or 4094).
 

Wendy

Joined Mar 24, 2008
21,938
That is a bit pricey. Shift registers are pretty cheap. If we ever hear back from the TS I'll look one up.
 

dannyf

Joined Sep 13, 2015
2,197
A simpler approach is to OR the output. For example, the first led would be connected to q9..0 through diodes so if any of the output is high, that led is on. The second diode would be connected to q9..1 through diodes, .... I'm assuming that you want 10 digit output here.

No change to your code.
 

Wendy

Joined Mar 24, 2008
21,938
Actually I mentioned steering diodes, but here is the rub, around 700 diodes, give or take, which is why I also said it was not very practical.

Add 45 or IC, plus 360 LEDs and it adds up quick.

An 8 bit shift register will require 45 IC with very little support circuitry, possibly transistors.
 

dannyf

Joined Sep 13, 2015
2,197
Static display has the advantage of low load on the cpu. However, a binary counter for such a large number of sequential outputs can be astronomical: you can calculate for example the pulses to turn on all 320 LEDs.

I suspect that you will need more computing power than available in the world to do that within a reasonable time frame.

Dynamic display will cut that time down exponentially. But requires considerable computing power as well.

You may want to explore alternatives.
 

Colin55

Joined Aug 27, 2015
519
"However, a binary counter for such a large number of sequential outputs can be astronomical: you can calculate for example the pulses to turn on all 320 LEDs.""

What are you talking about ???????????

Set-up will take less than 1mS
 

Wendy

Joined Mar 24, 2008
21,938
This is not a ripple counter, but a Johnson counter. I have not looked at your links yet, but 2^ does not enter into it. With a Johnson counter 360 outputs is 360 counts.

I mentioned the matrix approach to the LED Display, which is multiplexed.

I fixed your links, they weren't working. It would work, but it is not a binary counter, so some programming (which the TS has alluded to) would be required. It would be the simplest of all the approaches though.
 
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