What Arduino to chose?

I want to make my first Arduino project what do you guys recommend. I have a choice between Arduino Mega AVR ATmega1280-16AU and the Arduino Duemilanove 2009 both are a similar price so what should i choose ??

I want to reuse the board in the future, but at the moment I want to make a set of 100 led's turn on when a button is pressed and turn on for x amount of time before turning off when a different button is pressed.

With the 100 leds.. do you want to be able to turn on and off each LED individually? Do you want to be able to fade them in and out?

Think you need to do a bit more research on what you want to do, and also some of the Arduino Examples (even before buying, to understand em.) If you just want to turn on 100 LEDs when you push a button, you just need 100 LEDs, their resistors.. a button, and that's it.

If you want them to stay on after you push the button, could use ... alot of different choices, but an Arduino included. The only time you'll need the ATmega1280 (Arduino MEGA) would be... well, only if you need some extra analog inputs, outputs, and don't feel like buying extra components. (The Duemilanove / 2009 can handle 100 LEDs with just a few extra chips, the HC595's will do)

Between Arduino Mega and Duemilanove, if they are the same price (which I don't think so) buy MEGA which has more ram and I/O than Duemilanove.

If you're just starting and you can't buy MEGA really cheap, get Uno which is newer. Duemilanove is being replaced by Uno. http://www.robotsimple.com/Arduino/Arduino_Uno

but first find out what do you want to do with LEDs. Are some going to turn on at the same time? (so you don't need to control all of them individually). Do you want to use a shift register or you'd like to keep it simple by controlling each set of LEDs using one I/O pin?

Think you need to do a bit more research on what you want to do, and also some of the Arduino Examples (even before buying, to understand em.) If you just want to turn on 100 LEDs when you push a button, you just need 100 LEDs, their resistors… a button, and that’s it.

The reason I don’t want to go with the resistors and a 555 timer for delay is because I want more complex lighting effects such as a breath effect (diming) and in the future implement some more complex lighting such as Christmas tree style flashing and commands. These are just some ideas that I want to do to learn.

Between Arduino Mega and Duemilanove, if they are the same price (which I don’t think so) buy MEGA which has more ram and I/O than Duemilanove.

Arduino Mega $27aud http://goo.gl/v7x2P
Arduino Duemilanove $26aud http://goo.gl/J8sQ4

I want to keep it as simple as possible, at first I just want them to come on for x amount of time when a trigger is activated so if that is possible from the single I/o pin that that is great.

I am asking this with little research because I am asking for one as present for Christmas and need to get my act together and say what i want ;).

I have done some research and from what I can find the max led lights I can have on on one pin is 25 (20 * 25 = 500) assuming that 500 mA is the most I can have on any one port. So what shields, chips resistors do I need to run 100 leds ?

my xmas list so far (i have wire snips solder solder gun…)

Arduino Uno- http://goo.gl/f5gpa
bread board - 2x http://goo.gl/zopCJ or 1x http://goo.gl/f5gpa
Arduino Wire Jumpers 70x m2m - http://goo.gl/GXNHF
100 led - http://goo.gl/xlQTx

have you searched for any LED shield to get an idea? like this shield: http://timewitharduino.blogspot.com/2010/02/dual-bi-color-led-matrix-shield.html

It seems like you don't have a good idea about Arduino capabilities and your project's needs; you should do a bit more research. Mega328 can supply 25mA on a single port, but the ground and VCC pins can't do more than 200mA (more restrictions apply), so if you want to draw 20mA per LED, then you can have at most 10 LEDs driven directly from Mega328.

You can do this project using series of shift registers. You should do a bit more research and post more details of how you want it done. What are the LEDs setup and arrangement going to be? do you want to have matrix addressing or direct connection (would need more shift registers)?

You should also get some transistors for driving more LEDs. Then you can use a higher supply voltage (12V, 15V) and have longer columns of LEDs in series turn on with one control pin.

Here's an example where I had a 12V supply & used it to drive 20 LEDs. One arduino pin turned on the transistor to turn on the 20 LEDs. 2 other arduino pins turned on 2 other transistors to turn on 2 other sets of LEDs. I needed 5V for the LEDs, so I used a 7805 to regulate the 12V down to 5V.

I also used the left hand transistor to invert a data signal that I needed to go to the arduino (vs using a logic chip).

An easy solution might be Displayduino and LEDMatrix.

http://www.mondomatrix.com/