How to make a large LED chase effect?

I am looking to make a Xmas jumper with an LED chase effect to mimmic the snow falling.  I am having difficulties in deciding which is the best way to do this.

Essentially Think of having 8 strings of 8 LED's (to make it simple) and each string will have its own chase effect running.  I want these to be independent of one another, I.E. I don't want a constant LED line running down the jumper.

Now I have thought of two ways of doing this via Arduino:-

1) Simple Method - Using the ATMEGA328 to run each string of 8, providing its own running time and speed.

2) Difficult Method - Use a grid where one ATMEGA328 can run a 8x8 matrix.  This would require some transistors at each row and column and fancy code to produce the right effect.

Disadvantages of 1&2

1) Lots of wiring, 8 ATMEGA chips and power supplies

2) Unsure if this is possible, obviously I can switch quickly but to the eye would this even be visible.  For example if I wanted to power column A and row 1 and simultaneously power column D and row 5... would this power said LED's and also column A row 5 and column D row 1, all at the same time?

Any help would be greatly appreciated.  If I have overlooked any other methods, please feel free to mention them.

Thanks
Mo

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iceng1 year ago

If you like to solder, here are some fun chase circuits.

1] Uses the fact that the 4017 can advance on a rise or fall clock giving you a smooth transition 18 LED chase.

2] Is a trivial light house ckt.

3] Bill shows how a long LED string is wired.

18Lighthouse.PNGLITHOUSE1.jpg4017seq.gif
mokhaddoumi (author) 1 year ago

Perfect, thanks very much guys, going to check all these out tonight!

By far the easiest method: Use NeoPixels !

+1

Why build what already exists, just tell NeoPixals what you want to see in Basic or 'C' very easy and you can easily run 8 independent strips from a single uP.

Wiring is extremely simple..

New 'Ible about NeoPixel Xmas trees coming soon.....

-max-1 year ago

Just some good old TTL logic is all one would need to make it happen! a simple decade counter like the 4017 CMOS device and 555 timer will do the job, and you can make a bunch of completly separate modules. I did a similar thing using a string of 8 white LEDs on a breadboard, and used a 555 timer for a clock signal into a 74LS164 shift register, and fed the output of the last LED through a transistor inverting amp, back into the serial data in. This creates a really cool effect!

271828-1 year ago

You can use shift registers like the 74HC595, example:

https://www.arduino.cc/en/Tutorial/ShiftOut

Combine with Charlieplexing and you have an led dot matrix driver.

I would use a ring counter with a delay between the strings of LEDs.

rickharris1 year ago

Check out CHARLIEPLEXING - it's a way to run many LEDs from few outputs.