I've recently redecorated my master bedroom and would like to have some stars above the bed. I'm thinking 5mm warm white LEDs controlled by Arduino may be the way to go, but have 0 experience. I'd like to have the 12 popular zodiac constellations and 19 others, totaling, if I counted right, 388 stars. I don't wish to control each individual LED, not even so much each constellation. I would like to single out the zodiac constellations, and all the rest grouped together. My plan thus far, is to use push buttons to select the zodiacs, and a single pot switch to control (fade in/out) the other 19. The largest constellation would have 27 LEDs, I'm hoping I can control the constellations one channel each. A local store has the Mega, which would give me more than enough channels. So much so, I'm thinking I can pick a few (3-5) large stars and have them be RGB LEDs. I'm sure I'll need some accessories, though I'm not sure what is the best route to go about this.
Safe pin current of an Arduino is about 20mA, but there is also a max VCC/ground current.
It might be better to use an Uno/Nano and external LED drivers.
Leo..
Look on youtube for arduino led cube then just arduino leds. See how they do it and what it takes to make, some show.
Leds not fully bright (eye hurt at 1m or less) can run on 6mA to 10mA each if you want to add up power to get a supply good for at least twice your max current load.
I had posted a sketch that would make leds "twinkle" for someone (last year IIRC, maybe was 2015) by sharing time, only 1 in so-many leds (configurable, 3 to 6 range) was actually ON at any one instant. He didn't need many to appear lit at once and was using battery power so the savings mattered a lot.
Last I recall he ran into wiring problems. He was using heavy-duty house power wire (16 ga) to connect over 100 leds and the wiring was getting too thick to fit in his display base. I guess he had something on time (for wedding decor) but not what he had planned on.
You have many, many options for this project. Smart thing is to take time investigating options before you start any definite plans or buy anything but a board to start learning and practicing code with including checking out those options.
My questions are how you will have the wiring up there and could projecting lights on the ceiling (home planetarium) work?
Wawa
Safe pin current of an Arduino is about 20mA, but there is also a max VCC/ground current.
It might be better to use an Uno/Nano and external LED drivers.
Leo..
Perhaps more important is the 200mA safe total current limit.
I've had many people suggest projecting the stars, however I don't have a convenient spot for a projector. I had come across a project that used cat5 for the wiring, the most LEDs on one channel would be 27 so I hope it's sufficient. I assumed I would need some other parts, transistors or LED drivers, with whichever board I get. Was looking at shift registers for a minute, but figured the mega would be proper with it's many I/Os.