Hello all, I have a request for advice on a power management strategy for a project I’m working on. I am new to the world of electronics, this being my first project, and I’m a little unclear on some concepts that are probably very simple.
I’m still in the experimental/learning stage, and have found this website and other resources so incredibly helpful. Want to say thank you up front to everyone who takes the time to help newcomers like myself.
So, it may help to understand the project itself. It is somewhat of an architectural model that I intend to light up… It has 9 floors requiring internal lighting for the rooms: Ground floor requires 2 LEDs, then six floors above that with 8 LEDs per floor, above that two floors that require 7 LEDs each. It’s a total fluke this adds up to a convenient 64 floor lights btw, and these are all standard 5V20mA LEDs that I’m going to run at nominal (I bought a buttload of 100Ω 1/8W resistors for them).
Beyond these, the project will also require an LED for the building aerial strobe, 15 RGB SMDs and 2 RBG LEDs for internal/external seasonal lighting, perhaps a half dozen ‘flood light’ LEDs to simulate perimeter security, and a handful of other one-off LEDs for other effects plus whatever else I may decide to throw in because it’s fun!
These lights may, at times, be all or mostly all on, and I will need to address most of them individually, certainly so for the interior lighting. I’m going to try to simulate day/night hours when many or few room lights would be on (controlled at random in the code), lobby lights and outside lights always on, other lights being triggered manually, that kind of thing.
Long story short, I came to understand I cannot expect to power the entire system, all LEDs on at nominal power, through the Arduino (or can I?) and the shift registers I have (I bought 10 74HC595s) and needed to begin consider how to manage the power supply, and I came up with this experiment (forgive how crude this schematic is, it’s my first):
This is basically straight from the ShiftOut tutorial, except my goal was to split the power between the two sides of the transistors (npn2222’s). This is exactly what I’m looking at next to my laptop here, and it works. It took several iterations ironing out flickering and dimming, seems a well placed resistor always solved these issues.
Now, my questions!
Is this doing what I think it’s doing? Are the LEDs drawing the current they need and the Arduino/595 drawing what it needs, separate from one another but sharing a common ground?
If so, would it now be safe to place more LEDs in series through each transistor (ie, right now I have 2 LEDs per, but could I put 5 or 10 in each series for example?) My instinct is yes, based on I think (1) is true.
My intention is to continue to pursue the strategy in this schematic, add a second 595 to create an 8x8 matrix to light/control the 64 interior rooms, and then add a third 595 (and perhaps a fourth, fifth, etc) to begin controlling the rest of the lighting.
- Being that the first two 595s are operating as a matrix, is it even possible to add further shift registers that:
[ a ] Operate outside this matrix (Normal shift register behavior)?, or
[ b ] Constitute a completely new matrix (a third and fourth 595, a fifth and sixth, etc)?
- Am I even on the right track here? Or did I go off the rails long before any of my questions are even valid lol?
Anyways. Sorry for being so long winded here! I felt like I wanted to be thorough. Thanks in advance for your patience and any advice/criticism you may have!
ps. The schematic isn’t showing up in the preview, so I attached it as well.