[SOLVED] Looking for creative ideas to get 16 LEDs to flicker at "random" rates

[forrest_holleman]

Hi all,

I'm completely new to this forum, so I hope I am asking in the right area.

I'm working on building a toy for my 3 year old boy. What I am trying to do is to get 16 LEDs in a circuit to all flash independent of one another at seemingly random rates (probably in the 50-250 ms range) - to give a flickering/shimmering effect. In addition, I want to use a radial potentiometer to vary the brightness of the LEDs (as a collective) as well (i.e. as he turns the dial, the set of flickering LEDs all get brighter / dimmer together).

And to complicate matters - I want four sets of these (each with 16 LEDs and its own pot).

I'm assuming I'll need to use something like 555 timer circuit in conjunction with something.

Does anyone out there have any bright ideas as to how I might accomplish such a thing?

Thanks for any useful suggestions you might have.

This is just for a toy - it has no commercial use.

Thanks,

Forrest

 

[betwixt]

By far the simplest and cheapest approach is a small microcontroller with 16 output pins. These are very inexpensive. Generate either one 16-bit random number or two 8-bit numbers, whichever is easiest and send the number to the output pins. Connect the cathode (+) end of the LEDs to the output pins through current limiting resistors and join the anodes of all the LEDs together and to the output of an adjustable regulator (LM317 or similar). The regulator voltage will set the brightness.

Not sure where you are but total cost should be around $10 US.

You can do it with 555 timers but you need 16 of them and associated components, the cost would be much higher.

Brian.

 

[forrest_holleman]

"By far the simplest and cheapest approach is a small microcontroller with 16 output pins. These are very inexpensive. Generate either one 16-bit random number or two 8-bit numbers, whichever is easiest and send the number to the output pins. Connect the cathode (+) end of the LEDs to the output pins through current limiting resistors and join the anodes of all the LEDs together and to the output of an adjustable regulator (LM317 or similar). The regulator voltage will set the brightness."​

Hi Brian - Many thanks for the info - that definitely points me in the right direction. I'll start researching your recommended approach.

Kind Regards,

Forrest

 

[BradtheRad]

There are several creative circuits for yielding quasi-random flashes. Most start with a pulse generator, often a 555.

Several led flashers are at this link. Such as using a 4017 decade counter (scroll down to '10 Channel LED Sequencer'). Or 18 Stage LED Sequencer.

LED Sequencers, Flashers, Clocks, Faders

Example of taking different count pulses from pins of a 4020 or 4060 divider IC:

8 Random Flashing Leds Circuit

Driving led's from outputs of a 7-segment driver:

Random Blinking (Flashing) LED | Circuit Diagram

 

[mister_rf]

Also for a very simple solution you may use some specials RGB LED ( with only two pins).
Datasheet:
https://www.elektronik.ropla.eu/pdf/stock/ops/ostb5131a.pdf
This LEDs will automatically scroll through the RGB colors and fade into each color. You just need to supply it with 4-5V . There is an internal oscillator that controls the color change and the color sequences and the fade into a different color is slow (approximately 15-20 seconds for a change in color).
See the test I have made:

 

[forrest_holleman]

Thanks guys for your input and suggestions.

I found a simple solution - although it doesn't give me a different pseudo-random for each of the 16 LEDs as I had originally desired, it certainly provides enough variation to give the desired effect (and with 18 LEDS instead of 16).

I used this circuit - Christmas Decoration Project - but used all blue LEDs. The application is a toy stove for my little one who loves to "cook".... so I wanted to simulate four gas burners with flickering blue LEDs. This circuit uses a 4060B CMOS binary counter driving 3 sets of 6 LEDs - each set running at a different flash rate and at any given time, half of each set is in the on state, the other half in the off state. I put a pot on each to vary the intensity and voila - the wee one now has a pretty realistic 4-burner stove.

Next time I'll be a bit more specific regarding the application when posting for advice/ideas.

Anyway, thanks again for taking the time to reply.