Hello... and I messed up! Help, anyone?

Hi all,
I recently bought and Arduino, and I’ve been having a little remedial fun so far. I’m actually an artist by trade, but my dear old Dad was an electrical engineer, and I’ve always had an interest in such things (entirely opposite to painting pictures, which is what I do for my ‘day job’!). I’ve always felt that there is every bit as much art and grace in electronics as there is in any picture you might paint. There’s a simple beauty to electronics and engineering which has always appealed to me… anyway, I digress, but great to be here!

The whole Aduino thing has fascinated me since it arrived, and I’ve signed up for a few online courses/classes.

Here’s the deal… I saw an LED cube, and wanted to make one!
I got straight onto Ebay and ordered 500 RGB LED’s! (I’ve always been a little overenthusiastic!). The LED’s arrived today, and I now discover the are Common Cathode RGB LED’s!
Here’s the question… is there anything I can use these for, as in something decorative like the cube I intended making… or are they useless to me? help please… tell me straight?

I’ve actually just finished constructing a 5x5x5 single colour LED cube ( at least constructing it physically), and will be playing with tat using the arduiono and Shift Registers… I know… too ambitious, but I’m really enjoying learning, and I’m currently experimenting with Shift Registers via Youtube tutorials.

So… these CC RGB LED’s… any projects I can sensibly use them for? A nice LED matrix, maybe?
Am I just being too enthusiastic too soon?

Help? And thanks for let me bend your ear.
Best to all,
Tim.

Lookup how to use a P channel MOSFET as a digital switch (high side switch).

I've always felt that there is every bit as much art and grace in electronics as there is in any picture you might paint.

Until you let the magic smoke out. No grace at THAT point...

I got straight onto Ebay and ordered 500 RGB LED's! (I've always been a little overenthusiastic!).

Did you give ANY thought as to how you would power 500 LEDs?

is there anything I can use these for, as in something decorative like the cube I intended making... or are they useless to me?

Depends on whether you intend to use the Arduino, or not.

The Arduino can control common cathode RGB LEDs as easily as common anode ones. The problem is that if you PWM the common cathode, all three colors will be the same intensity, as opposed to being able to PWM the cathodes individually in the common anode case.

Yeay, you can use them. But you need a NPN (BJT) or n-channel (MOSFET) transistor to drive it.

Let me explain for a 2D thing matrix.

Connect all the cathodes of each column to each other. Connect each column to the collector of a NPN. Connect the base of the NPN via a resistor to an Arduino (or shift register output).

Connect for each row the anodes of the row per color to each other. But a resistor in line per color per row. Connect that to an Arduino (or shift register).

For an 8x8 you now have:
8 times a column via a NPN. Make the base high to enable the column.
8 x 3 = 24 rows connected to drive each row and color. Make it high to enable the row.

Now scan the columns by making then high one by one. And per column set the 24 rows high for the pixels you want to turn on.

But, indeed, 500 led's is mad :stuck_out_tongue: Start with a 2x3x3 or something :stuck_out_tongue:

tim104:
I got straight onto Ebay and ordered 500 RGB LED's! (I've always been a little overenthusiastic!). The LED's arrived today, and I now discover the are Common Cathode RGB LED's!
Here's the question... is there anything I can use these for, as in something decorative like the cube I intended making... or are they useless to me? help please... tell me straight?

500 RGB LEDs?

I'd suggest that you use your LEDs to build something like the "Infinity Mirrored Room" made by Yayoi Kusama.

Hard to believe, but I read in the text that he just used 75 LEDs.

Perhaps you do it a little bit bigger than he did in his installation?

P.S.: You will also need a lot of mirrors, too.
:wink:

PaulS:
The Arduino can control common cathode RGB LEDs as easily as common anode ones. The problem is that if you PWM the common cathode, all three colors will be the same intensity, as opposed to being able to PWM the cathodes individually in the common anode case.

So just do the PWM on the anode then.