Forum, I need some help in how to power some LED segments in a safe manner being driven from a Arduino Nano. Attached is a drawing of what everything I could think of. And just to also let you know I am very new to this stuff so by all means not an expert. I would be in the beginner category. The LEDs will change color scenes with a button (not pictured). Would like to have a button for each scene but that is a question for some other time. I have read up on power injection and things like that but I wanted to hear from the forum your expert advice on how to do this safely. I would also like to know what minimum gauge wire I can use to make this work. I would like to use these power adapters if at all possible (web link below) but I will let you guys guide me. One other thing to note is each LED will be lit to white (highest intensity) so my calculations use 60mA per LED. I appreciate your time and help! Alitove 5V power supply
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The sum total of your currents exceeds 20 Amps, though actually the maximum draw of each WS2812 is generally quoted as 55 mA. You would need at least two of those rather expensive adapters. I don't like the look of the output cable on that adapter for 10 Amps either.
There are difficulties using multiple adapters in parallel, some concern they may be unstable if connected together and if you divide up your strips into groups with separate 5 V connection (but of course, common ground) there are concerns about connections between potentially powered and unpowered sections under odd circumstances. A single power supply (30 A) would be a better choice, mounted in a reasonably large protective enclosure.
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Now the strips as you gather, cannot carry anywhere near the necessary current, you do need to provide a main power cable all the way along the display, I would think you really should use 2 mm2 wire - such as used to wire to mains power outlets - for this purpose and cross-connect this to the start and end of each strip.
While it might not actually be necessary to connect to the end of each strip as well in terms of power, it is important that the data and ground line always travel together so you have to have data and ground connect at the end of one strip and go to the start of the next, so you may as well use the main cable to connect at that point and run the data wire alongside it. Because you have some length between the strips, as well as the 470 Ohm resistor in series with the data input to the first strip, you should have the same resistor in series with the data input at each strip section.
Connect the power supply to the main cable wherever it is convenient, but probably best not at the Nano. The Nano can be fed power back from the start of the first strip along with the data wire, this bundle of three wires need not be particularly heavy.
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Paul__B, thanks for the response and information! I have a lot to absorb on what you posted with. Let me edit the drawing (in png format ) to see if I understand you correctly. I will post it for you to review when I have it completed. Thanks again!
Paul__B, I updated the drawing to what I think you are describing to me. Not totally sure, but attached is rev 2. Also, when you say 2 mm2 I am assuming that 14 gauge strand is good. I looked at a wire chart and 14 gauge is equal to 2.08 mm2 conductor cross section. Also, can the data wires (green) between LED segments and the 3 wires going back to the nano be 20 or 22 gauge wire (mm2 equivalent .032 and .0253 respectively)?
That's not good for the V- wire; connect it up the same as V+. Otherwise, ever increasing amounts of ground current go thru the strips from the lower right to the upper left.
Now, a classic "newbie" mistake there regarding understanding electricity.
Electricity travels around a circuit and somebody's "law" from long ago is that the current is the same in all parts of the circuit - you cannot have electrons piling up in one part and being depleted in another.
So you have to understand that the current in the ground wires is the same as the current in the "supply" - 5 V wires. Whatever you do for the supply, you must do exactly the same for the ground. As I said, they must run together as a pair, generally using twin or "figure-8" cable.
And the data line which indeed does not need to be anywhere as heavy, 22 gauge sounds just fine as the current in these is minuscule, but it must again, travel alongside the ground so where you show power connected to the end of one row, back to the main cable and up to the start of the next row, the data wire must also follow that path, tied to the power cable. There must be no wires following separate paths.
No. Connect V- in between each pair of strips at a minimum, which is basically what the red V+ wires are doing.
Even better would be a black wire with each red wire.
Thank you and Paul__B for the help!! Are there special 3 way connectors I need to use for all those 3 way connections? And this one power supply will power the arduino nano to with no issues? Just seems strange with all this current going around the circuit, the Nano won't blow up. I really don't understand electrical circuits that much at all but just want to make sure this is a safe circuit I am building.
Almost right, but you show red and black going separate ways.
It makes little difference where you actually feed the power supply into the strips, given that you have the heavy "backbone" cable, but the 5 V and ground go everywhere together, never separate. And the data wire just tags along with them.
The only concern regarding the Nano is that you will have a very substantial power supply feeding this all. The Nano will only draw what it needs, which is not very much, but should something short out in or near the Nano, you just might set its wiring on fire. You could put a 1 Amp fuse in series with (only) the 5 V line where it branches away from the LED strips to feed the Nano.
I see what what you mean about separate ways. Let me redraw one more time and resubmit to you guys. Want to make sure its right because I will need to submit the drawing to the drumline director with a bill of materials.
I think I have this right. Added in the 1 amp fuse. Would you put a fuse on the +V power supply line (30 amp fuse)? I know the power supply has built in safety features. These LEDs will be on a drumline prop with kids around it. Just want to make sure it is as safe as possible. Thanks again for the help guys!
) to see if I understand you correctly. I will post it for you to review when I have it completed. Thanks again!
