Thankyou for the response.
I am relatively new to electronics, hardware and Arduino however I've worked as a software engineer and have plenty of programming experience.
In hindsight, I can see that I haven't provided an adequate amount of detail. I think I've incorrectly assumed that almost all ws8212b LED strips are the same. I'll do my best to go into detail of my findings and understanding here, however if I misuse some technical terminology please understand that the electronics concepts are all relatively new to me.
The ws8212b LED strips are black, non-waterproof and come in rolls of 5 meters, where there are 60 LEDs per meter (Thus 300 LEDs per roll). I have two of these rolls, thus 600 LEDs or 10 meters. You can cut these strips into smaller strips, which is what I intend to do for this project (20 strips of 20 LEDs for a 20x20 matrix). They also operate at the 4.5 - 5.5 volt range.
According to the manufacturer, Each LED is made up of three(Red, Green, Blue) smaller LEDs that at full brightness draw 20mA each. This means that a LED showing white at full brightness would draw 60mA.
When you consider a chain of 300 LEDs or 5 meters in series at full white brightness, this would draw an enormous 18,000mA or 18 amps (60 * 300 / 1000). If I were to chain 400 LEDs or 6.67 meters in series at full white brightness, this would draw an even larger 24,000mA. This of course, isn't even considering the current draw of the other components in the circuit.
It is to my understanding, that by putting the label "The LED strips must not exceed 5 meters, when used in a DC series circuit", the manufacturer is noting that the max current draw of 5 meters worth of all white, full brightness LEDs should not be exceeded. Either this, or that the voltage drop will be so significant at 5m that they should not be wired this way.
The actual project, is that I wish to make a few small arcade-style games where the RGB LED matrix serves as a screen and each LED serves as a pixel. With this considered, I feel that I must note that:
- Only around 25% to 40% of the lights will be on at any one time during a game.
- I will be using a brightness of around 50% for all lights.
50% of 24 amps is 12 amps, and 25% to 40% of this gives a range of 3 to 4.8 amps.
With all of this considered along with the other components in the project and so that I have ample room to adjust the brightness up, I have elected to start with a 5v 10 amp power supply.
I understand that at this point, I've possibly answered my own question because if the strips aren't going to draw more than 18 amps anyway, then surely there's no sense worrying about voiding that 5m warning. I've figured this as the warning most likely has to do with going over a maximum current of 18 amps and the LEDs / strips wire not being able to deal with it.
Even though I never intend to do this, I would still like to wire my circuit under the ideology that I could connect a 24 amp power supply instead and set all lights as white at full brightness without issues because my matrix was wired to support it.
With that all out of the way, now onto my question...
Due to my lack of understanding of electronics, I'm not 100% sure if the way I wish to wire my matrix qualifies as a "DC series circuit" and will void the manufacturers 5m rule. Obviously in a literal sense I'm using 400 LEDs or 6.67 meters WORTH of ws2182b strip which if wired in one long line would clearly void the manufacturers rule.
I may be misunderstanding this, but I've come across this diagram and and link...
https://ledstripstudio.com/hardware-connections-examples/
By using something called "power injection" or "voltage injection" I should, theoretically be able to chain 20 rows of 20 LEDs with the same data pin, without the entire strip's massive current draw going through every row.
For example, if the matrix was to display red at every pixel at 50% brightness, I would expect it to draw 4,000mA in total (20mA / 2 * 400). If I were to measure the current on any given row however, I would wish to find a reading of 200mA which is 1/20th of the total current of 4000mA. For this to work, one thing I have noted is that the wire I'd use for my "power lines" would have to be thicker than others as the total current of each row would indeed flow through these.
My most pending question is, is this possible? Is it possible to wire a 20x20 ws2812b matrix in such a way with 1 data pin, but many intermittent power injections to ensure that the current remains reasonable and doesn't void the 5m warning for "DC series circuit"? Is the circuit I've described even qualify as a "DC series circuit"?
Thankyou for your time.
You do not want to run the data back from the end of one row to the "start" of the next. You arrange the rows in alternate data directions so that the end of the first row on the right, feeds directly to the start of the second row on the right in a zig-zag pattern. Now the libraries which are written to control matrices deliberately allow for such an arrangement because it is the only practical way to do it. In particular,it is important that wherever the data flows from one part to the next, the ground must accompany it.