Hi Hans,
I don't think i will be buying that program anytime soon! but it looks pretty sweet!

Can you tell me more about the ICs you used in your sample? Specifically the last one that combines them all together. Even if you just provide a few sample part numbers i can lookup the pinouts and then i will put it together in a new schematic.
Thanks again!
Nate

 

Hi Nate,

I would like to send you the entire schematic and a layout as well. Since the files are Eagle format with suffixes .sch and .brd they are not accepted as an attachment in posts.

The board is pretty small and has only one layer with the exception of a single jumper.

Forward your email-address in a PM and you'll receive the files right away.

In the meanwhile you might want to look where to purchase NE556 and CD4017 (ST-name HCF4017). The prefixes are different depending on the manufacturer. The numeric name is unchanged.

These are the only two ICs involved in the circuits. Different from audioguru's statement you don't need many parts for a random number generator.

All you need for a complete circuit:

four resistors, five capacitors and two ICs

Regards

Hans

 

Hi hans,
your random number generator turns on one LED at random. I don't know if the time between each LED lighting will also be random.

I thought that 30 LEDs were going to be used. Wouldn't they look more random if a different quantity of them lighted each time?

__________________
Uncle $crooge

 

Hi audioguru,

the LEDs of course stay on the same time since the 4017 is positive edge triggered. However the pattern is unpredictable because of the very much unequal frequencies of both astable multivibrators. (850Hz and 180Hz) If you just use one counter with 30 LEDs connected to 10 outputs the pattern won't look boring if the LEDs connected to same output are not mounted adjacent.

I watched the LEDs for a while and it might even happen, that 9 of 10 are omitted within one full cycle to have the same LED twinkle twice in a sequence.

I'll go one more step and try to find the best way to cascade counters, either using the highest count output to clock the next stage or use the carry out as a clock signal and probably use a separate astable for the count inhibit of each counter.

I'll tell you about the result when finished.

I already have a good idea for practical use. Mount the LEDs on the ceiling of your wife's bedroom. So she'll have twinkling "stars" even if the sky is overcast and it's raining cats and dogs. (Maybe it will be a good reason for divorce too. I don't know.)

Hans

 

LOL.. thats just about what i am trying to do! LOL

I really appreciate the back and forth too. Its helpful to see different perspectives.

I think If i set this circuit up I will have it power a set of 10 LEDs, and setup 2 completely separate circuits for the other 20 LEDs. That way each of the 10 LEDs are random, and each set of 10 LEDs is controlled separately. The way i see it, the most LEDs that could possibly be lit at once moment is 3. And that is only if each separate circuit happens to trigger an LED at the same exact time....

as for the timing of how long each LED is lit, and how long in between each light... i will have to consider that later....

Thanks again guys!
Nate

 

I have Eagle Light now, and I am ready to start playing with it. Send over the files whenever you can.
Thanks!
Nate

 

I've got one of these stars from Gooligum Electronics, it's got a tiny 8 pin PIC and 20 Charlieplexed LEDs. You'll want to use very bright LEDs as it's got a 1:20 duty for each LED.

__________________
Bill
Smart Kits build Smart People
http://www.blueroomelectronics.com

 

LOL What the heck is charlieplexing??? sounds like a wrestling move...

Is it similar to multiplexing?

 

It's really fancy multiplexing, but only one led on at a time. Great for the pin frugal among us. A matrix display is much easier to drive.

__________________
Bill
Smart Kits build Smart People
http://www.blueroomelectronics.com

 

What's so bad about charlieplexing? It helps saving copper.

 

Nothing. Works like a charm.

__________________
Bill
Smart Kits build Smart People
http://www.blueroomelectronics.com

 

This is a really nice project. I was thinking about doing something like this as well but wasn't sure where to start. I was intending to use it for lighting in a fish tank to simulate the lighting effect you get from a pool thats inside.

 

Hi all interested in the circuit,

I've played a little with the circuit for more LEDs. Using the CARRY output of the preceeding stage the next counter will count in logical sequence: BACKWARDS!

Using the same high clock signal for all stages the count inhibit inputs must have different frequencies. Otherwise the same light pattern applies to every stage. The frequencies used are: 850Hz for main clock, 180Hz for the first count inhibit input and 126Hz for the second count inhibit. (126Hz due to standard value parts used).

The same main clock signal takes care of equal on time for the LEDs. With 20 LEDs the circuit already looks pretty confusing.

Trevors, I guess this circuit is just right for your application. The twinkling is very short though, but the effect will be the same as looking at water waves reflecting the sun.

Another good application idea: Carve a wooden diamond and use the LEDs on it. Your wife will love you for the hugest diamond in the world.

Here is a screenshot of 20 LEDs.

Hans

 

Nothing at all, apart from it's obvious limitations.

Not with only two LED's it doesn't!

I think that was Bill's point, why use two I/O pins to charlieplex two LED's, when you could just use the two pins to feed an LED each?.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

Can you send a full-resolution image? I am trying to reproduce your schematic in Eagle, and I think i almost have it.
I cannot seem to find the section to test the circuit out (animate it)

Thanks for your time!!
Nate