Flashing LED design feasibility, help

Projects General Guidance
1

Hey guys,

I am currently brainstorming ideas to create a handmade Christmas present for my girlfriend. I would like to create a sign with three words that light up sequentially ( think " I love you" for future examples, although the message is more personal than that).

Referring to the "I love you" example I want the "I" to light up then the "love" and finally the "you" in sequence. I was thinking of making these each with a decent amount of LEDs put into a wood board. It would probably end in me using somewhere around 75 LEDs for the whole board to be the size I would like. I would essentially like to have each section connected to one port, but it can be split if needed.

I also would like to include a dip switch or some setting control on the back she could press to change the blinking pattern or control the lights in certain ways.

I have done a decent amount of work with the Arduino Mega 2560 and i am comfortable with writing the code. My questions would be these:

Is this best to do with arduino? If so, which board ( I was thinking nano)?

Can any of the boards source enough current to power these LEDs or am i looking at an external power supply? I would really like her to only have to plug in one thing.

Thank you for any help in advance

2

Your first problem will be that a Nano does not have enough pins to control 75 leds directly. You will have to look at multiplexing (software or hardware) or port expanders / shift registers.

A Nano can't deliver enough current through its 5V output to drive all 75 leds at the same time. So you will need another power supply; if you limit the current per led to 10mA and have all leds on at the same time, you need at least 750mA and to play it safe add a 20% margin. Add the power for the Nano and I would think that a 1A power supply would be the minimum.

The other limitations of the Nano's processor are 20mA per pin, 100mA per port and 200mA through the processor's Vcc and Gnd.

If you use additional hardware, you will need to look at the current limitations of that.

3

I have seen some people mention WS2812 strips and i think i could manage the project using this instead of individual LEDS, but I am not familiar with them. My biggest goal is for her to only have to plug in one thing for it. Do you think the project would be more feasible this way?