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### Topic: Any one willing to help out a DIY noob? (Read 2750 times)previous topic - next topic

#### Artomoz

##### Apr 06, 2011, 02:34 pm
I came on here to desperately ask for some guidance from experts or hobbyist like myself.

I'm new to this arduino (uno) coding (C++) and have minute knowledge on how to code anything.

Lets just get to the point.

I'm trying to implement 7-9 60mm 8x8 led RGB matrix screens to a helmet I'm constructing.

After doing some google "research" I stumbled upon a very simplistic looking thing known as the "rainbowduino" created by seeedstudio and wondered if it is really necessary to buy such item?

Can I achieve the same outcome with out having to spend money on expensive additions?

Now like stated before, I'm very new to this do forgive me if I'm very ignorant. I will give it my best to understand and do my own research on what you guys give me.

I just don't want to spend over \$200.00 + dollars and not be able to do a thing with the led matrix and the rainbowduino.

#### Grumpy_Mike

#1
##### Apr 06, 2011, 08:10 pm
Quote
I'm trying to implement 7-9 60mm 8x8 led RGB matrix screens

So that's 7 * 8 * 8 * 3 = 1344 LEDs - that is an quite a lot of LEDs to control.

The rainbowduino is just an arduino with built in drivers. It means you have one processor to handle the multiplexing (or refreshing) of each matrix. It is not a bad solution, you could probably make it cheaper if you made it yourself but it is a very big project for a beginner.

#### Artomoz

#2
##### Apr 07, 2011, 10:03 am
So that's 7 * 8 * 8 * 3 = 1344 LEDs - that is an quite a lot of LEDs to control.

The rainbowduino is just an arduino with built in drivers. It means you have one processor to handle the multiplexing (or refreshing) of each matrix. It is not a bad solution, you could probably make it cheaper if you made it yourself but it is a very big project for a beginner.
[/quote]

I believe it's only 448 LEDs. 8 * 8 * 7= 448 Unless I'm missing a few.

So you recommened to buy 7 rainbowduinos since it will be easier to work with, right?

#### Artomoz

#3
##### Apr 07, 2011, 10:09 am
You most likely know more than I do about this. What type of power do you recommend?

I'm inclined to use 2 lithium ion batteries for it to power up the whole thing but I'm sure it will need loads of energy to even survive for a few hours.

#### tomm

#4
##### Apr 07, 2011, 10:38 am
Technically each LED in the RGB array is 3 LEDs, that's why you have the 8*8*3.

#### Simpson_Jr

#5
##### Apr 07, 2011, 10:51 am
I'm afraid Mike's right....

To change the color/intensity of each led you'll need "special" ones with 4 legs. They may look like a single LED, but house 3. On of the legs is common and with the other three you can drive exactly the colour you want. Not turning on green while powering red and blue will give you purple light as long/short as you like.

There's also the RGB _flashing_ LED with just two pins, which changes colour by it self. Problem with this one is that you can't change colour on command. It also houses 3 Leds and... a small processing unit which runs a program by itself.

When it decides to turn purple while you would like to see green, there's unfortunately nothing you can do.

#### Artomoz

#6
##### Apr 07, 2011, 04:48 pm

Technically each LED in the RGB array is 3 LEDs, that's why you have the 8*8*3.

Ah, you're right! How can I be so stupid and not realize this?! haha. Thank you for the explanation.

#### Artomoz

#7
##### Apr 07, 2011, 05:09 pm

I'm afraid Mike's right....

To change the color/intensity of each led you'll need "special" ones with 4 legs. They may look like a single LED, but house 3. On of the legs is common and with the other three you can drive exactly the colour you want. Not turning on green while powering red and blue will give you purple light as long/short as you like.

There's also the RGB _flashing_ LED with just two pins, which changes colour by it self. Problem with this one is that you can't change colour on command. It also houses 3 Leds and... a small processing unit which runs a program by itself.

When it decides to turn purple while you would like to see green, there's unfortunately nothing you can do.

To be honest that was going to be my next question. Unfortunately I have 2 packs of 2 pin LEDS left over from my previous project one slow auto flashing RGB and a fast flashing RGB pack. I did notice what you stated it couldn't exactly be controlled since it flashed randomly. The only thing that could be controlled was the delay which sort of was a way for me to get a desired pattern going but unfortunately like you stated; if I wanted purple I got green. haha.

I will pay a visit to Radioshack and buy a 3 pin LED RGB light for an exaggerated price today and run some tests to get use to the coding.

As far as controlling the LED what codes do I need to send?

Now, what exactly is multiplexing? I kind of read a couple of articles about it and it basically was sending the code to the desired LEDs with out activating other LEDs on the same grid.

I'm guessing the rainbowduino makes multiplexing easier?

Thank-you for the response.

#### tomm

#8
##### Apr 07, 2011, 05:13 pm
Multiplexing uses persistence of vision to rapidly turn single LEDs or groups of LEDs on and off, but so fast that it looks like they are always on. It's useful when certain components in a project don't allow all the LEDs to be on at the same time. For example, if you were using your arduino to power a lot of LEDs, you would be limited to having a certain number on at any given time.

#### Artomoz

#9
##### Apr 07, 2011, 05:20 pm

Multiplexing uses persistence of vision to rapidly turn single LEDs or groups of LEDs on and off, but so fast that it looks like they are always on. It's useful when certain components in a project don't allow all the LEDs to be on at the same time. For example, if you were using your arduino to power a lot of LEDs, you would be limited to having a certain number on at any given time.

Ah, that makes sense. Do you believe it will be necessary if I use the rainbowduino though?

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