WS2812B - Strip length and powering

Hey all. I’ve been working with ws2812b’s for a little bit. Got the main addressing and simple powering under control. I have one question about wiring larger strips up.
I am using an arduino mega.
If my Powersupply is having voltage sag over a 150 LED length.

Would it be possible to split the strips into x2 75 LED strips and connecting like so

Please explain why this wouldnt work…

Well, it might be an improvement, but the proper way to do it it to run a decent cable alongside the strip to bring 5 V and ground to each end and tap in every 75 LEDs.

Also, do not power the Arduino with 9 V via the "barrel jack" or "Vin". The board runs on 5 V - you have 5 V - so connect the 5 V along with the data and ground connections as a bundle from the start of the strip back to the Arduino "5V" pin.

Paul__B:
Well, it might be an improvement, but the proper way to do it it to run a decent cable alongside the strip to bring 5 V and ground to each end and tap in every 75 LEDs.
Also, do not power the Arduino with 9 V via the “barrel jack” or “Vin”. The board runs on 5 V - you have 5 V - so connect the 5 V along with the data and ground connections as a bundle from the start of the strip back to the Arduino “5V” pin.

Thanks for the quick reply!

Sorry i am using an Arduino Mega so the 9v is needed. From what i’ve read its a pain to run a mega off of 5v. Thats the reason for my thought of running the 5v supply from the center of the two strips.

pathogenex:
From what I've read its a pain to run a mega off of 5v.

Rubbish! :roll_eyes: What utter nonsense! :astonished:

Running either a Mega or a UNO or Nano from the internal regulator is a really bad idea! It will work as long as you do not connect anything to the "5V" pin that requires significant current or power many things from the I/O pins because that current is of course, also drawn from the 5 V line.

I repeat - the Arduino runs of 5 V. Providing a regulated 5 V supply is the most sensible way.

And there is a particular concern that powering the controller from a different 5 V supply than the LED strips risks damage to the first LED if the controller is driving it but the LED strip power supply fails. That is the main reason why you should have a 330 (or 470) Ohm series resistor in the data line at the LED strip. As well as the 470 µF or 1 mF capacitor across the 5 V power at the same point.

Paul__B:
Rubbish! :roll_eyes: What utter nonsense! :astonished:

Running either a Mega or a UNO or Nano from the internal regulator is a really bad idea! It will work as long as you do not connect anything to the "5V" pin that requires significant current or power many things from the I/O pins because that current is of course, also drawn from the 5 V line.

I repeat - the Arduino runs of 5 V. Providing a regulated 5 V supply is the most sensible way.

Are we talking about the same mega? I'm using the Mega 2560 which the store page states
Input Voltage (recommended) 7-12V
Input Voltage (limit) 6-20V
EDIT - Even though the store page suggests this I have managed to get it powered up and running both strips from the single PSU.

https://store.arduino.cc/arduino-mega-2560-rev3

Paul__B:
And there is a particular concern that powering the controller from a different 5 V supply than the LED strips risks damage to the first LED if the controller is driving it but the LED strip power supply fails. That is the main reason why you should have a 330 (or 470) Ohm series resistor in the data line at the LED strip. As well as the 470 µF or 1 mF capacitor across the 5 V power at the same point.

Would you suggest wiring the arduino from the start (left side) of the first strip? I want to avoid extra power cables if i can.

Thanks again for your help +1 karma

pathogenex:
Are we talking about the same mega? I’m using the Mega 2560 which the store page states
Input Voltage (recommended) 7-12V
Input Voltage (limit) 6-20V

And indeed it does say that.

This is a perennial problem. :roll_eyes:

A very real danger is that the obsolete tutorials on the Arduino site and others misleadingly imply that the largely ornamental “barrel jack” and “Vin” connections to the on-board regulator allow a usable source of 5 V power. This is absolutely not the case. It is essentially only for demonstration use of the bare board back in the very beginning of the Arduino project when “9V” transformer-rectifier-capacitor power packs were common and this was a practical way to power a lone Arduino board for initial demonstration purposes. And even then it was limited because an unloaded 9 V transformer-rectifier-capacitor supply would generally provide over 12 V which the regulator could barely handle.

If you are asking this question, it is highly likely that you will wish to connect something else. In which case, the answer is regulated 5 V.

This is because the on-board regulator is essentially capable of powering only the microcontroller itself and no more than a couple of indicator LEDs. The on-board regulator might be able to power a few other things if it had a heatsink, but on the (older) Arduinos, it does not.

Powering via the “barrel jack” or “Vin” connections is asking for trouble. The “5V” pin is not by any means an output pin, if anything a “reference” pin but most certainly the preferred pin to which to supply a regulated 5 V.

pathogenex:
Would you suggest wiring the Arduino from the start (left side) of the first strip? I want to avoid extra power cables if i can.

And that is exactly what I advised in the first reply. :grinning:

Are we talking about the same mega? I'm using the Mega 2560 which the store page states
Input Voltage (recommended) 7-12V
Input Voltage (limit) 6-20V

You are confusing the Mega board with the processor on the board which runs at 5V.
The board provides regulation for the processor, nothing much else apart from the USB interface, which is powered by the USB cable.

It is nonsense to suggest you can’t run a Mega processor off 5V, it fact you will destroy it if you try and run the processor at 6V or over.

After every 50 LEDs, you need to increase the power supply if you want the same LED lighting. These LEDs take 30-60 milli amperes. So after 50 ice is already 3 amps.

Paul__B:

pathogenex:
Are we talking about the same mega? I'm using the Mega 2560 which the store page states
Input Voltage (recommended) 7-12V
Input Voltage (limit) 6-20V

And indeed it does say that.

This is a perennial problem. :roll_eyes:

There is a good reason for it being a perennial problem - the product page also states:

5V. This pin outputs a regulated 5V from the regulator on the board. The board can be supplied with power either from the DC power jack (7 - 12V), the USB connector (5V), or the VIN pin of the board (7-12V). Supplying voltage via the 5V or 3.3V pins bypasses the regulator, and can damage your board. We don't advise it.

Indeed it does.

Unfortunately, whoever is responsible for the product page has no apparent interest in updating or correcting it in any way. :roll_eyes:

This is indeed, a perennial problem with the information in many places on the Arduino site.

Nowhere near as bad as "information" on the "instructables" site however. :grinning:

atilka25:
After every 50 LEDs, you need to increase the power supply if you want the same LED lighting. These LEDs take 30-60 milli amperes. So after 50 ice is already 3 amps.

No you no not need to increase the power supply, what ever that means.

The power supply needs to be able to supply sufficient current for the LEDs, use 60mA per LED as a guide. Also the voltage drop across the high resistance PCB traces needs mitigating by wiring the power supply to both ends of the strip, and with a longer strip even to the middle as well.