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Topic: RGB LED Strip external power source (Read 4296 times) previous topic - next topic

MrDankYT

I am planning on putting RGB Lights on my electronic scooter, the WS2812b kind, dont worry i already got everything planned except the use of the power source and stuffs, i got a battery and a 12A 15v-5v DC step down, but will the ATmega328P Nano V3 Arduino be able to hold up to around 5A of current in 5v? im guessing no? So since the LED strip has +, -, and data, will it be enough to plug up the arduino into a 5v power bank outlet and let the data wire from the led strip go into the arduino while the + and - goes into the actual battery?

Summary: Can i put the data wire from an LED strip to an arduino while the actual + and - is to another power source?

THANKS FOR ANY RESPONSES!!!! I AM NEW TO PROGRAMMING AND WORKING WITH ARDUINOS!

Paul__B

None of the 5 A of current ever passes through the Nano.

The step-down converter connects directly to (both ends of) the LED strip.  Three wires - 5V, ground and the control wire - come back from the connection to the LED strip, to the Nano, supplying power to the Nano 5V ("Vcc") terminal and taking the control signal to the LED strip.  The control wire has a 470 Ohm resistor in series where it connects to the LED strip.

MrDankYT

So putting the output from the step down converter directly into the led strip then putting a normal 5v 1a usb wire from a power bank to power the nano, then you connect the data wire to the data pin that is specified in the programming? Im asking because i saw someone in a video put a usb from his computer into the nano then the output to the led strips would be from the nano itself, along with the data wire, and i was kinda skeptical about that actually working

Paul__B

And you certainly should be sceptical.

Connect to the Vcc, ground and a data pin.  Forget the USB - it is for programming (or if you have a real-time connection to a PC).  Keep all wires running together.


MrDankYT

Ok had some fun in a circuit builder program and is this correct then?

Paul__B


Almost, but you have omitted the wire from the 5 V terminal on the LED strip back to the 5 V terminal on the Nano, the 470 Ohm resistor at the data input terminal on the LED strip and the 100 µF capacitor between 5 V and ground at the LED strip itself.

Grumpy_Mike

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is this correct then?
No.
The LEDs in the strip are drawn upside down.
You have no seriese resistor in the data line, 220 to 510R is needed.
You have no large capacitor across the input to the strip.
You have no power going to the Nano so it will only work when plugged into a computer.

MrDankYT

Sure the LED is upside down but i got it from a library from a random person online, so what do you expect, and im only trying to put out a + and - input, if i wouldn't have had that sketch of a led strip i would just draw a box and have 3 wires sticking out of it and label it as a led strip, and you care alot about the leds being upside down but not about the data wire just disapearing?

And i thought that the nano would be plugged in was kinda obvious?? i wasn't gonna bother with drawing in a cable.

However about the Resistor i understand, i just forgot to draw that in, but why is a capacitor needed??

MrDankYT


Almost, but you have omitted the wire from the 5 V terminal on the LED strip back to the 5 V terminal on the Nano, the 470 Ohm resistor at the data input terminal on the LED strip and the 100 µF capacitor between 5 V and ground at the LED strip itself.
I dont really understand where you're supposed to put the capacitor? by connecting it 1 wire from the capacitor to the 5v going into the led strip then the other wire going into the ground that is also going into the led strip?

Paul__B

I don't really understand where you're supposed to put the capacitor? by connecting it 1 wire from the capacitor to the 5v going into the led strip then the other wire going into the ground that is also going into the led strip?
Yes, the capacitor goes in parallel with the 5 V and ground wires at the LED strip.

You may say that there is a capacitor already in the output of the step down converter, but these LEDs are touchy and you really need to provide a bypass at the very input with as short wires as possible.

And I thought that the Nano would be plugged in was kinda obvious?? I wasn't gonna bother with drawing in a cable.
Plugged in to what?  When we answer questions here, believe me, nothing is obvious, "bothering" is absolutely critical; many problems people have relate to a simple detail that is obvious - at least to the person who has done it many times and got it right but ...

I am always keen to reinforce the concept that the three wires carrying power back from the LED strip connection and signal forward to the LED strip run together as a bundle and are not separated.

Grumpy_Mike

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Sure the LED is upside down but i got it from a library from a random person online, so what do you expect, and im only trying to put out a + and - input, if i wouldn't have had that sketch of a led strip i would just draw a box and have 3 wires sticking out of it and label it as a led strip, and you care alot about the leds being upside down but not about the data wire just disapearing?
Thing is if you draw something and it is wrong, it is wrong no matter what your excuse. How are we to know you don't cair?

These sorts of things raise alarm bells when you know what you are doing. Yes just a box would have been better.

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However about the Resistor i understand, i just forgot to draw that in
And

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but why is a capacitor needed??
So how can we tell what you just forgot and what you do not know, we are not mind readers.

Deva_Rishi

The Capacitor isn't really needed, since there should be  a big enough one in the stepdown 15v-5v  if it's a good one.
To 'Correct' you have to be Correct. (and not be condescending..)

MrDankYT

Ok i redrew it is this fine now?

Paul__B

The Capacitor isn't really needed, since there should be  a big enough one in the stepdown 15v-5v  if it's a good one.
So, you either failed to read, or simply did not understand my previous post then?

OK i redrew it is this fine now?
Let's see:


Well, a very poor diagram which does not covey a sense of order in the project.

I personally do not care a fig about which way up the diodes are in the box.  Since they are not diodes anyway but actual ASIC ICs, better to simply have three wires stuck out the side of the box which do not pretend to attach to the diode wires.

A diagram which confuses the direction of signal and/ or power flow makes it difficult to follow, and somewhat worse is one which muddles the polarities.  Almost always now, ground is the negative supply and your supply feed is the positive.  It is expected that ground is at the bottom and VCC - positive is at the top.  Swapping them over in the step down converter is a source of confusion and having the ground wire make a "home run" to connect is not only confusing, but visually works against my admonition to keep all the wires closely together.

And given that you have a 5 V regulated supply, it makes no sense whatsoever to supply the Nano with a power bank; just wire it from the LED strip as I explain in every previous post here.

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