I am working on a Christmas gift for my boyfriend who is a computer engineer, and also likes to tinker with the Arduino, and has built a DIY 3d printer, so for me, the work involved in making this is just as much of the gift as what will be going in the shadow box.
I want to wire 48 LEDs around the inside on the box.
16 along the top and bottom, and 8 along each side

I've been doing a lot of research, and picking his brain as much as I can without giving away too much, and while I understand a lot of what I should do, im struggling a bit to envision exactly how it should be laid out

I intend to use a 12v power supply, and will run the Arduino using a battery pack.
I have looked into running both off the 12v power supply, with a tipp120 transistor as a gate, but have been advised that may not be the best option, although this would allow me to run them all in series which I would greatly prefer.

So besides wanting to know if my vision for how the wiring of the leds will work, or if it wont, why? but also how do I integrate the switch between the Arduino and the power supply to the leds to turn them on, and be able to run on/off sequences.

From my research. the most viable way to wire them is in sets of 3 or 4, in series, and then running multiple sets of series in parallel.

The leds I intend to use are white 3mm 2.8-3.2v and 20mah

Any input, advice or help would really be appreciated as i'd like to not only figure out the exact layout prior to ordering everything, but also want to do it right the first time.

If any of my thoughts or understandings at this point are completely wrong please let me know, this is a world I am just learning and have very little experience in, and most of my knowledge has come from researching.

I've attached a schematic I've put together for me to better visualize how the leds should be wired. hope that helps

Thank you

 

Welcome to AAC!

Since you want to be able to sequence the LEDs, my suggestion is to wire them as a matrix (e.g. 6x8) and only turn one of them on at a time (but multiplexing fast enough so they all look like they're on). You'll want to operate at a higher peak current so that the average is around 20mA. That would allow you to have the Arduino and LEDs operate from the same power supply. Multiplexing will also save power because you won't have all 48 on at the same time.

You can vary brightness by controlling the duty cycle of the signal that turns on the LEDs.

I'm currently playing around with a 4x4x4 LED cube. I'm controlling the LEDs with 8 I/O's; but I allow up to 4 LEDs to be on at the same time.

Can the I/O's on your Arduino source/sink enough current to drive an LED directly? That would simplify the circuitry.

 

Welcome to AAC!

Since you want to be able to sequence the LEDs, my suggestion is to wire them as a matrix (e.g. 6x8) and only turn one of them on at a time (but multiplexing fast enough so they all look like they're on). You'll want to operate at a higher peak current so that the average is around 20mA. That would allow you to have the Arduino and LEDs operate from the same power supply. Multiplexing will also save power because you won't have all 48 on at the same time.

You can vary brightness by controlling the duty cycle of the signal that turns on the LEDs.

I'm currently playing around with a 4x4x4 LED cube. I'm controlling the LEDs with 8 I/O's; but I allow up to 4 LEDs to be on at the same time.

Can the I/O's on your Arduino source/sink enough current to drive an LED directly? That would simplify the circuitry.

Thank you for all the suggestions and help.
The idea of running it on a matrix intrigues me as it would allow for more customization as well.
Would each set essentially be it's own circut?

I have the Kumon uno board, which can output up to 5v so yes it could light up a single led.
In terms of power sourcing, I'd really prefer to only have one necessary power source, rather than driving power to the Arduino board and LEDs separately.

 

Thank you for all the suggestions and help.
The idea of running it on a matrix intrigues me as it would allow for more customization as well.
Would each set essentially be it's own circut?

You have the option of being able to operate each LED individually. But the wiring will be more complicated.

I have the Kumon uno board, which can output up to 5v so yes it could light up a single led.
In terms of power sourcing, I'd really prefer to only have one necessary power source, rather than driving power to the Arduino board and LEDs separately.

Operating at 5V and being able to sink/source 100mA are two different things. Some microcontrollers will sink or source 20-ish mA. When you multiplex, you want the average current to be around 20mA. The LEDs I'm using can be driven at 500mA (very briefly). I chose around 75mA. My I/O's can only sink/source a few mA, so I need to use external transistors.

 

You have the option of being able to operate each LED individually. But the wiring will be more complicated.
Operating at 5V and being able to sink/source 100mA are two different things. Some microcontrollers will sink or source 20-ish mA. When you multiplex, you want the average current to be around 20mA. The LEDs I'm using can be driven at 500mA (very briefly). I chose around 75mA. My I/O's can only sink/source a few mA, so I need to use external transistors.

Forget individual LEDs and use a neopixel strip. Much less wiring involved but a bit more programming, however a myriad of special effects are possible. Lots of info out there on the internet but here is a good place to start;

https://learn.adafruit.com/adafruit-neopixel-uberguide

 

Forget individual LEDs and use a neopixel strip.

That's not how I work. When someone asks for help, I offer it using their ideas. After all, it's their project, not mine or yours.

 

Forget individual LEDs and use a neopixel strip. Much less wiring involved but a bit more programming, however a myriad of special effects are possible. Lots of info out there on the internet but here is a good place to start;

https://learn.adafruit.com/adafruit-neopixel-uberguide

Thank you, and while I realize using a led strip would be much easier and less complicated, the effort put into the wiring and engineering of it is just as much of the gift as the shadow box itself.
This is my backup plan, if I end up running out of time to do the more complex build.
Thanks

 

You have the option of being able to operate each LED individually. But the wiring will be more complicated.
Operating at 5V and being able to sink/source 100mA are two different things. Some microcontrollers will sink or source 20-ish mA. When you multiplex, you want the average current to be around 20mA. The LEDs I'm using can be driven at 500mA (very briefly). I chose around 75mA. My I/O's can only sink/source a few mA, so I need to use external transistors.

Thank you, you've given me some things to think about and research!
I may be back to pick your brain a bit more on this.
Appreciate your help.
Once I research and have a better understanding of of this process hopefully will become clear if this is the route I'd like to take!!