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Topic: Help/ guidance with arduino LED project (Read 1 time) previous topic - next topic


I'm a industrial design student currently involved in a project that requires 2 sets of flashing LED's  (I refer to them as 'banks' of LED's, but I'm sure there's a more appropriate name for this)

I need to make a bank of 12 LED's and another bank of 12 LED's flash independently of each other. I would like each bank to flash at different frequencies per/sec and hopefully at different levels of brightness at some points.

I'm a total arduino novice, in fact I barely know anything about electronic engineering so it's proven a bit difficult to find the code and examples I need to make this happen.

The idea is that the banks of LED's will cycle through different flashing frequencies, changing every 30 seconds, or perhaps every minute. I would like to have them flash in unison a couple of times as well.
Overall the flashing loop needs to go for about 3 minutes. And I'm hoping that I might be able to add a button to begin the sequence, and if I can wrap my head around it, maybe even a reset button if the 3 minutes needs to be interrupted.

The project requires high intensity white LED's, I think they're 3volt 5000MLC. to be wired up 4x4 in each bank.

I have managed to use a breadboard to get 2 sets of 3x3 LED arrays (18 all up) to flash in unison running straight off pin 13. I had some help briefly from someone with arduino knowledge and he worked out that I could do this without resistors by chance. However I cannot separate the 2 banks this way as they never flash together because of the delay (I think)

I also had help to rig up sets of 3 LED's in parallel but must have misunderstood as I was using a 12 volt battery and had 330K ohm resistors but it doesn't appear I took the information down correctly.

I'm really stuck as I've wasted a lot of time trying to ask the right questions, learn arduino language and figure out how to adapt the limited things I have come across.

I wondering if I'm expecting too much, and whether I can make this happen (in the next 5 days..) given my level of experience..? any thoughts or help would be very much appreciated as I'm like a fish out of water...



You should be able to get that going in 5 days, but start with the one bank as you had it but first read


and  the sticky  http://arduino.cc/forum/index.php/topic,97455.0.html

You must have a resistor in series with every "string" of LEDs,  and 330K is much too high, the resistor will be below 1K,  start off with 330 ohms, and when you have everything working, calculate the final value for best brightness.

I dont know how you could get a 3x3 bank of 3 volt LEDs to work from an arduino pin, they would need 9 volts at least .

You will need a buffer to drive each string of  LEDS (transistor or ULN2003 which has 7 of them )

There are ways to multiplex the display, but you might not have time to master it.

Pin 13 is handy as it has its own indicator LED ( and resistor ) but rather use pins 11 and 12 as they can be pulse width modulated to change the brightness.

Start off with one LED with a 330 ohm resistor on pin 11, change the pin number on the blink-without-delay example from 13 to 11, and  then get it to do what you want by experimenting with similar "blink-without-delay" and "for "  type routines within that routine.

Once you have the one LED blinking in the pattern you need, try the pulse width modulation to vary the brightness ( with its own similar patterns but with different values or whatever you need )

Then connect another LED and resistor to pin 12 and do the same.

once you are happy connect the buffers and LED banks.

Good luck
45 years of editing projects with a knife and soldering iron, then I found Arduino !


Lachstock1, take a look at this video:

This is a setup consisting of several individual Arduino-clones running two LED strings each.  Basically it was a project that got repurposed for my window for christmas.  There's one master controller sending an RF signal every 30 seconds (I think) to all the rest, and the others will change their displayed sequence based on that signal.  (Each controller has an RF module on them to send/receive data, in this case only one was sending and the rest were receiving.)

Now, while this is not exactly what you're wanting to do, the initial idea is there.  The two "banks" of LEDs you're talking about can easily be translated to the individual strings in my setup.  One controller, two separate strings.  Each string gets data separate from each other.  At about 30 seconds in, you'll see a raindrop effect.  Each string behaves different from the other on the same controller.  The same applies to the color sparkles effect immediately thereafter, each string behaves separate from the other.  The effect at about 2:23 has both strings doing the same thing together.

Anyway, just thought I'd show you it's very possible to do what you're wanting to do.


Thanks for the pointers guys, I really appreciate it. I checked out the forum posts you shot me Boffin1 and you were right- the blink without delay has been the most applicable code to use.

I sorted out my led resistors and wiring so now too so it's just a matter of sorting the code. I've just posted again with my current predicament if either of you feel like having a look.

Again, thanks for taking the time to comment of my project!

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