Is My Project Feasible?

Hi, I'm looking to build my first big Arduino project. What I'm planning on doing is basically upping the scale on some very simple circuits and code. My main concern is whether or not this project would work, mainly in the sense of a power supply...

I would like to have 512 buttons, 512 leds, 64 74HC595's (shift out), and 64 74HC165N's (shift in). Basically it would be an array of 512 buttons being brought into Arduino then corresponding LEDs lighting up when buttons are pressed.

What I'm concerned about is my power supply, and whether or not at 5V power supply can adequately light up 512 leds. (I have no electronics background)


What I'm concerned about is my power supply, and whether or not at 5V power supply can adequately light up 512 leds. (I have no electronics background)

5vdc power supplies come in all sizes of current. How big you need kind of depends on how you use your leds as if you want to be able to have them all powered on at the same time then that's over 10 amp just for the leds, at another couple of amps for those chips then you might want a 15amp 5vdc power supply for all that. The good news is that doesn't have to be very expensive, as between older PC power supplies, E-bay, and 'surplus dealers' finding a supply should not be all that difficult. I would look into converting an older PC power supply as those things can be found for almost nothing.


you might also want to brush up on multiplexing

That's an ambitious project for a self-reported newbie at electronics! Are you sure you don't want to start with something like 32 LED's? 64 LED's?

retrolefty is right, you will need a power supply in the >10A range which begins to raise questions about how you're going to efficiently wire things. If you try to pass 10A through regular 24AWG hookup wire you're going to lose a lot of power.

I'd recommend breaking things up into modules: each module capable of handling N switches and N LED's (N=8 might make a nice start) and then slowly growing the system to see at what point things start breaking down (if you've done the design well then it won't break down at all!)

The Gadget Shield: accelerometer, RGB LED, IR transmit/receive, speaker, microphone, light sensor, potentiometer, pushbuttons

I'd do what RC said. Make a small board with one input SR and one output SR, thus 8 IOs. Organize the board so the data in and data out pins on the SRs come in from one side and go out on the other. When you have that working make more boards and start daisy-chaining them.

Eventually you will need 64 boards, if you do it like this they are all connected in series and you don't have to worry about driving 64 clock and data lines but it will be slow(ish). But if it's just for people to press a button and see a LED then that's OK.


Where are you guys coming up with that much current?

74HC595 is only good to 6mA x 512 = 3A.
QA?QH, IOH = ?6 mA @ VCC = 4.5V
QA?QH, IOL = 6 mA

Can get a load of buttons here pretty cheap
Non-Illuminated Pushbutton Switches - Surplus Sales of Nebraska, 17 cents each

Superbright LEDs like these don't need 20mA,, 18 cents each
They are really bright on much less!
Current limit resistor,
330 Ohm 1/4W Resistor ±1% 330R 331 - dipmicro electronics 1 cents each

I 2nd (3rd?) the recommendation to do it as modules.
Can get ten 100cmx100cm boards for $25 from itead studios, $29.90 with shipping, takes 3 weeks
design a board or two (you haven't spoken to organization yet),
maybe using SPI (3 pins,Clock, Dataout (MOSI), Datain (MISO)) and 8 SS lines to quickly shift in/out of each board (vs software shiftIn/shiftOut, much slower).

Alright, thank you all for your replies! I now have a much better idea of what direction to go in. I'll definitely build some test modules, and will have to learn about multiplexing! Thanks