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Breathing LED Lamp - Need Help!

AndyLanderdahl

Sep 8, 2015
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So I'm making a lamp for a friend of mine for her dorm room. It's a log with some glowing mushrooms on it basically.
Now I have two problems, or maybe one, not sure. I need to find a way to power 20 LEDs (3V 20ma) off 120VAC. Now I do have a 12V power supply that I think should work, but that would mean putting them in some series. Which would conflict with the next problem. She'd like each of the individual lights to breath on its own, but all together would work too. Now my second power option was all 20 in series with a 3.3k ohm resistor (rated at 2W) which as far as I know should work ok to dim them all with a sufficiently rated circuit (the only simple one I found was based on a 555 chip to power 1 LED). The whole resistor is only dissipating ~1.3W so I think 2W should be ok? But that doesn't account for the individual breathing effect.

Basically the best solution I've come up with was to make a breathing circuit for each LED and power them all in parallel, but this would take up a lot of space. And space is definitely at a premium. I looked into using a microprocessor, but I really couldn't find anything, and I know very, very little about them.

SO in short, I guess what I'm trying to say is, can someone suggest a solution to power 20 LEDs (3V 20ma) off 120VAC so that they each breathe independently (timing and frequency)? I do have a 12VDC power supply that I think can handle 1A, so that should sufficiently power it, I think 12V is a lot more manageable for this project.

Sorry, this is my first post, and I have a weird amount of electronics knowledge (I inexplicably know things, as well as don't know things (mostly only with IC chips though).
 

AndyLanderdahl

Sep 8, 2015
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Ah, yes, sorry. You know when a light fades in and out? Similarly to how you would breathe in and out?
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
25,510
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25,510
if you apply 120V directly to a LED then it will expire. But you can only do it once :)

one option is to use addressable LEDs and a small microcontroller. The LEDs are all connected together and the microcontroller can program the court and brightness of each.

I'd go for the you're that have power, clock, and data pins as they are the simplest to drive.

these are available in strips, but you can also purchase the individual devices or cut the stood and solder wires to them so you can mount them wherever you like.
 

AndyLanderdahl

Sep 8, 2015
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if you apply 120V directly to a LED then it will expire. But you can only do it once :)
Yes, I fully understand that, which is why I said my idea was to wire 20 of them in series with a resistor.

one option is to use addressable LEDs and a small microcontroller. The LEDs are all connected together and the microcontroller can program the court and brightness of each.

I'd go for the you're that have power, clock, and data pins as they are the simplest to drive.

these are available in strips, but you can also purchase the individual devices or cut the stood and solder wires to them so you can mount them wherever you like.
Do you have any recommendations for a microcontroller that would be able to handle 20 outputs? Or I could use a couple to reach the required outputs.

I had originally thought it would be much easier to use an addressable LED strip, but I need the lights to be reasonably far apart from one another, since the lights are inside the caps of the mushrooms, and then they just have leads that go down the stem and through the wood and protrude out the back. I'll do a quick search and see if I can find single addressable LEDs? Then I can just run wire between them, and that should cover the spacing quite well.

EDIT*** I didn't find any single LEDs, but seems like it wouldn't be hard to cut them off a strip right?
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
25,510
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25,510
yep cutting them off a strip is possibly a viable option. You only need 2 outputs to drive a string of these, so you can possibly use something simple like a picaxe.
 

AndyLanderdahl

Sep 8, 2015
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Sep 8, 2015
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Awesome! That's what I was hoping for, since it sounds like it'll take up very little space. Thanks!

Unfortunately I don't have a clue how that accomplish it. I know a bit about addressable LEDs, very little about microcontrollers. After a quick Google, I didn't find anything unfortunately. Could you give a quick explanation on where to connect the the chip, as well as how to program it? I have zero experience coding (unless you count HTML, lol).
 
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