1st post.... noob alert!

:wink:

Greetings all!
Very excited about what I am seeing here, and am in need of advice.

Been scouring this site for the last day or two, looking at the code, and the schematics... fun fun fun!

Specifically the project I am trying to accomplish is this:http://arduino.cc/en/Tutorial/Loop

I need a config that will not only run a loop, but I need that same set of instructions to be on an identical set of LED's. So, 12 LED's (2x6LEDs) running in an identical pattern.

Is it possible to hook 2 LED's to each hook up, so that the HIGH is sent to two LED's simultaneously? or is that a quick way to need to purchase another board? :slight_smile:

Also, a chase loop is not the only effect, I want to create a gentle, gradual "throb/pulse effect" from the LED's... oh yeah, and I want to use RGB LED's. Will likley incorporate a button to select with, and depending on how smoothly I pick this up, a pot may be used for speed control.

I've seen some videos of a long LED chase board that someone put together using RGB LED's, and they were using the "octocode" from this forum.... is that ringing any bells for anyone? (I've not found it yet)

So, in a nutshell, I need two groups of 6 LED's doing the exact same effect, weather I have it set for a chase, or a strobe, or a throb/pulse.

I'm looking to purchase my first board and get started on this thing soon, yes, because I am that excited, but would absolutely love any advice from the braintrust here that would keep me from wasting time on blind alleys and dead ends.

Much appreciated on any guidance that can be provided by you all.

Thank you for your patience while I work through this. I am a relative noob with electronics, but I have a good basic understanding of LED circuit requirements, as well as a healthy respect for electricity! :wink:

Looking forward to kicking this off, thanks again!
-=Tech-Daddy

Oh, and I know about this: http://arduino.cc/en/Tutorial/Loop

Actually had it in the original post.... but since it was my first post, it would not let me put a link in! (that is a creative policy you guys have there! Nice work!)

Is it possible to hook 2 LED's to each hook up, so that the HIGH is sent to two LED's simultaneously?

Yes but make sure each LED has it's own resistor and make sure you don't exceed the maximum current out of a pin. The limit is 40mA but I would stick to below 30mA if possible.

but since it was my first post, it would not let me put a link in! (that is a creative policy you guys have there! Nice work!)

This was implemented to cut back on spam postings and it is remarkably effective so don't knock it. :wink:

Thanks mike! Something I just thought of is that the RGB LED's have 3 legs plus a common. That's 18 legs per side to control.
32 legs total...

Hrmmmm .... guess I need to start looking at RGB multiple LED chase configs and see how they did those.
:wink:

32 ?

12 RGB leds

12 * 3 = 32 ?? are you sure .

Im making one to control 16 RGB leds and the way Im going to do it is via i2c and 6 * 16 bit (mcp23016) chips

Ohhhhhh my.... I'm climbing into bed now and pulling the covers over my head.... how embarrassing!

BWAHAHA!!!

My friends call it "Craig math", sorry about that.

But you get the drift of what I am talking about.
I may make my first one with blue LED's just to lower the complexity. Then after I get that one working right, I'll bump it up to an RBG LED set...

Looking at my success for math, I'm likley doing myself a huge favor by keeping it simple! :wink:

-=TD

Ok, looking at 3mm LED's, and the ones I have are rated 20mA, and if I try and put 2 per pin like I was asking about earlier, then I am pushing the 40mA per pin... I don't like that.

So now, let me downscale this from an RGB setup to a single color (blue) setup, driving 12 LED's, 5v/20mA configuration in a loop. My guess from reading, is that I will need an LED driver of some sort.

Another question that I was wondering about.

I've seen the posts that talk about the power supply. 5v - 12v is the rated range of these boards, and 7v is what is recommended.

My tinkering with a computer PSU for the past umpteen years shows me that there is indeed a 5v line and a 12v line. 5v is marginal supply, 12v will waste wattage. But I remember a trick that I read somewhere, where someone wanted 7v to a computer fan (to make it run slower, and they used a combination of the 12v line and the 5v line, like this: http://www.dslwebserver.com/main/fr_index.html?/main/5-7-adapter.html

Would this work on these boards to properly supply the optimal 7v without using a wall socket transformer? Computer PSU's are DC already, the supply is there.

What are the dangers? I've tied LED's together for years using the 5v rail of power supplies (properly resistored, of course), but I certainly dont want to blow up my new toy... :wink:

for the driver look up ULN2803A.

the computer p.s.u is a little over kill for 12 RGB leds, But just use the 5v rail .

Ok, looking at 3mm LED's, and the ones I have are rated 20mA,

They might be rated at 20mA but if you run them at 10mA they are nearly as bright and you can run two quite safely. In fact do a test I think you will be hard pushed to see the brightness difference between an LED running at 15mA and one running at 20mA.

What are the dangers?

You have a ground connection that is 5V above the ground of the power supply. This has the potential for causing hefty currents to flow if you accidentally connect things up wrong. I wouldn't do it myself.

Thanks you two! Much appreciated.
"yes", a computer PSU is overkill, however if I am putting the LED controller inside a computer, I certainly dont need an extra set of power lines and a transformer cable coming out. It should be an inclusive environment, needs to be an inclusive environment. Maybe an inline fuse of some sort to keep the amperage to <1A?

@ Mike -
I've always gone off of the manufacturer recommended amperage. I do have an LED tester that allows me to drop the LED in at various mA levels, didn't even think about the running the LED below the specs. Did not think it would work. WIll check it out tonight.

2@10-15mA seems much more tollerable! :wink:

I've always gone off of the manufacturer recommended amperage.

Using a component at less than the maximum rating is known a de-rating and is a technique that you use to make a design more reliable. De-rating at between 50% to 80% is standard commercial practice for maximising the reliability and component life.