# WS2812b LED Strip and Arduino Nano.

Hello there

The WS2812b LED strip is gonna be a 5V 60LED/meter

I have a question about a upcomming project that i will be working on. im planning on doing some backlight on two displates. each plate is gonna need around 230cm of LED strip. and i wish to connect them to the same controller, would it be possible to buy a 5 meter LED strip, cut it to lenght and then solder wires between the two pictures, the length between them will be a max of 10cm.

As of the arduino Nano. im planning on running it with a 5V 2A powersupply. Will it be possible to power both the LED and the Arduino from the same powersupply, or do i need a seperate Power supply, and where would i have to connect the powersupply on the Arduino?

Yes. I don't see any problemâ€¦

A simple way to power the UNO is to cannibalise a USB cable and feed your 5 and GND into it using the USB connector.

You can use just one i/o pin and use logic to determine what data to feed to the entire strip all at once at whatever rate you require.

The dOUT of one section can be fed to the dIN of the other. If my metric system chops are right your distances are considered short, relatively and should neither be a problem.

Use a large capacitor as advised in tutorialsâ€¦ I'd put one on each strip maybe overkill. Feed the first strip through a 470 resistor, again as advised in tutorials.

You might detect that I think browsing tutorials or watching some YouTube won't be a waste of time.

I do animations and try to achieve 100 frames per second, a one meter strip is possible with plenty of leftover time to compute you LED contents.

a7

I do see a major problem: your power supply

Each WS2812 LED is made of 3 LEDs internally. Normally, we use 20mA figure for the maximum consuption of each LED.

2.3 m @ 60 LEDs per meter = 138 WS2812 per strip.

138 x 3 LEDs = 414 LEDs total

Worst case scenario (all LEDs at full brightness) 414 x 0.020 amp = 8.28 amps

This is for 1 strip, and you say you will have 2 strips..... We are talking he about 16+ amps. A 2 amps power supply won't do the job.

Plus, this mean that you PCB trace, at the beginning of the strip, will carry, potentially 8+ amps. Not sure they are designed for such a big current

You lights will serve as a heater at the same time ! You will need to interrupt the power bus and start a new one.

Of course, chances are that you will never let them all ON at full brightness, for minutes but proper design should plan for that !

Haha, yikes. The metric system is supposed to make things easy, it is clear I need coffee.

So yes, power a problem. @jasmino also correctly points out you might not need max current to every pixel all the timeâ€¦

And the LEDs are very bright.

So figure out how many how bright at once. To plan for max current to all LEDs at once is nice, but I have never come anywhere near needing that calculated curretn.

Best: use a power supply that can provide more than plenty of juice, do some experiments and then select the power supply for deployment.

If you havenâ€™t one, an adjustable power supply is a nice piece of equipment for the lab. You can DIY or get one all ready to go, depends on where you want to spend your time and money.

You can get the logic working with a wimpy power supply simply by using low brightness or shorter strips. Write the code having this in mind will make that approach easier.

a7 / 10.

Thank you very much for your responses.

I am aware that they will be very bright when on full brightness. I was planning on running less than 50% brightness or perhaps even less than that. i will have to do some testing with this before final assembly.

As a second question. Would it be possible to cut the LED strip and then solder them together with some wires and they will still be working properly or is that simply a no go. so i use the same pins on the arduino

OK being careful here or tryingâ€¦

See reply #1: Yes you can split a strip and use wires to re-create the connections you severed in order to have a wide gap.

They can all run off one pin, or use two strip objects if you think it would simplify your software. I use one pin always and figure it out in the logic.

10cm no problem. That is 4 inches, right?

a7

Yes, that's 4 inches

I have done projects with 1 m no problem

If you want to go like 5, 10 m or even more, capacitance might become a problem

alto777:
OK being careful here or tryingâ€¦

See reply #1: Yes you can split a strip and use wires to re-create the connections you severed in order to have a wide gap.

They can all run off one pin, or use two strip objects if you think it would simplify your software. I use one pin always and figure it out in the logic.

10cm no problem. That is 4 inches, right?

a7

alto777:
A simple way to power the UNO is to cannibalise a USB cable and feed your 5 and GND into it using the USB connector.

a7

:o :o :o :o :o :o :o
Just connect the 5V power supply to the gnd and 5V pins on the NANO board.
No cannibalization required.
Tom...

You need a power supply that can handle all LEDs at full brightness. Mind that an LED running at 50% brightness is fully on 50% of the time, and fully off 50% of the time. That's how those things are dimmed. Your eyes do the averaging of the brightness. A 5V 20A supply is cheap, no reason to skimp on that.

You need wiring that can handle that current - the strips themselves are not up to the job. You have to connect your main power wires to both ends, and make one or even two connections in between (for each 2.6m section!). This way the main current will run through the power wires, not the thin traces in the strip. A strip 2m long powered from one side will have markedly lower brightness on the far end.

A power supply point every 1m is best; in your case one halfway would give 1.3m sections between power points. That limits the local currents in the strip to about 2A, where the mid point would feed up to 4A into the strip (2A in each direction). Size your wires accordingly.

The strips are designed to be cut between every LED, you see the solder pads. Of course you can connect those together with wires again, just keep the currents in mind: the split between the two sections is a perfect point for additional power.

The same 5V supply can also power the Arduino; I'd put a Pi filter in between to get rid of the switching noise of all those LEDs.

"You need a power supply that can handle all LEDs at full brightness. "

Not if you aren't going to run them all at full brightness for any significant time. There's a crap-ton of devices around here running perfectly fine with a power supply selected for the current measured when the device is running off a higher capacity supply.

Perhaps it does make sense to use a brick-sized power supply just in case you ever do want to. Handle all LEDs at full brightness. In the meantime, that's one of the functions of capacitors. To let you handle something that does draw large currents in between times of drawing no current.

a7

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