Sequencing LEDs

Thread Starter

craigfoo

Joined May 16, 2013
22
I have 12 LEDs that I want to turn on/off in this order:

Each one will be on for a period of time before shutting off.

1 on

2 on

1 off / 3 on

2 off / 4 on

3 off / 5 on

4 off / 6 on

5 off / 7 on

6 off / 8 on

7 off / 9 on

8 off /10 on

9 off / 11 on

10 off / 12 on

11 off

12 off

I think a MCU would be best for this but is there something I can do in the analog domain? I was thinking a couple of 555 timers but then my part count is getting high. Thoughts?
 

gerty

Joined Aug 30, 2007
1,269
I have 12 LEDs that I want to turn on/off in this order:

Each one will be on for a period of time before shutting off.

1 on

2 on

1 off / 3 on What about #2

2 off / 4 on What about #1-3

3 off / 5 on

4 off / 6 on

5 off / 7 on

6 off / 8 on

7 off / 9 on

8 off /10 on

9 off / 11 on

10 off / 12 on

11 off

12 off

I think a MCU would be best for this but is there something I can do in the analog domain? I was thinking a couple of 555 timers but then my part count is getting high. Thoughts?
You need to give more info, see questions above, and
fill in the rest of the blanks
 

Thread Starter

craigfoo

Joined May 16, 2013
22
For example:

Each LED is on for 30 secs with a 15 sec interval between them. They're cascading.

LED1 comes on
LED2 comes on 15 secs after LED1
LED1 turns off after 30 secs of being on, LED3 turns on
LED2 turns off after 30 secs of being on, LED4 turns on
etc.
 

gerty

Joined Aug 30, 2007
1,269
Sounds like what you're looking for is the "Knight Rider " circuit, always 2 on at a time. I think I have one somewhere , let me take a look.
 

Bernard

Joined Aug 7, 2008
5,357
How about a 555 15 sec clock, 2 cascaded 4017's, 12 NOR's, & 12 inverting drivers?
Or substitute 2, 8 stage parallel out shift registers & anotrer 555 for the 4017's?
 
Last edited:

Thread Starter

craigfoo

Joined May 16, 2013
22
Thanks Gerty, these are cool!

Bernard, doing a little more research, I was thinking of something similar. How about two 555 timers each at a 30 sec clock and two 4017s. The first 555/4017 set would run the "odd" LEDs (LED1, LED3, etc.) and the second 555/4017 would start 15 secs later and run the "even" ones.
 

Bernard

Joined Aug 7, 2008
5,357
absf, your statememt is exactly what I was going to say this morning, except you had the full schematic to go with it. Only question now is this a continuous operation or does it start & stop?
 

absf

Joined Dec 29, 2010
1,942
absf, your statememt is exactly what I was going to say this morning, except you had the full schematic to go with it. Only question now is this a continuous operation or does it start & stop?
It is continuously running once the sequence ends, it would start all over again. If it should stop after running one cycle, I would put a NAND gate at the output of the 555.

But I agree with Bob that using a uC is the best solution.

Allen
 

Thread Starter

craigfoo

Joined May 16, 2013
22
Great feedback! Thanks!

A uC does seem like the right solution but how would that affect the cost of getting a circuit like this manufactured? I would think that dealing with programming a part would be a much greater cost than just having an open loop, no software solution. Does anyone have experience with this?
 
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