How many strips per output pin?

Hi,

Just a quick question.

Is it possible to link more than 1 led strip to 1 Arduino output pin?

For example, I wish to make a fan of led strips connected to just 1 output pin.

The idea is that all the strips would operate in harmony with each other at the same time.

So each strip would light up at the same time and in the same manner.

Would that work please?

Martin

Yes. That works fine. As you are already aware, you can't control each strip individually in this manner, but you can control them all in parallel.

Just make sure that your power supply for all those strips is up to the task.

I assume you are using NeoPixels (WS2812) or something similar? These addressable RGB LEDs have a driver chips built-in. They just need a "little" (low power) data connection from the Arduino (and a common ground) and that can be shared.

Hi,

Thanks for the replies!

Yes, I am using ws2812b strips, they are only going to be about 8" long, so a total length of about 56".

The power supply will be used to power some other fairly short strips but is 10 amp so that will be enough.

Martin

BTW, Adafruit says...
https://learn.adafruit.com/adafruit-neopixel-uberguide/arduino-library-use#faq-2894547

image

Hi,

Thanks for the information.

Is 4 a set limit or does it depend on the number of leds on each strip as I hope to use 7 strips with 25 leds per strip.

As that is only 175 leds do you think that would work?

Martin

No, the number of LEDs following the strip doesn't matter.
It is judged only by the number of branches.

I think 4 is considered to be a fairly safety value.
You can test it to see what number of branches works fine.

Hi,

OK, thanks I'll do that.8-))

Martin

I've never tried it but I'd expect you could drive many-many more... The datasheet lists input current at 1 microamp and the Arduino can put-out up-to 40 milliamps.

Input capacitance isn't specified and that could be the limiting factor, but I'd guess you can control more than 4 strips.

I also would have thought that the fan in would mean you could drive many strips from one I/O pin.

In these very fora, however, have been presented problems with doing.

While I never argue with success, I also never argue with failure. I assume Adadfruit publishes its advisory for a good reason.

This is not the time for uninformed advice or guesswork. There are real solutions.

a7

Thanks for the replies. :smiley:

The other option is to use 7 pins which gives a lot more options to control the strips in many different ways which could be the better option.

I will think about it and decide which way to go.

Martin

You could also just run 7 * 25 = 175 LEDs on one strip and take care in software to just duplicate the pattern of the first 25 to subsequent groups of 25.

There is no advantage to running 7 pins to 7 strips unless you have a time issue and would need to update only a small strip of 25. Updating 175 LEDs should still allow a decent frame rate for any effects you program.

The real advantage to not sharing 1 data to 7 strips is the gain in flexibility, as has been observed.

a7

Hi,

Brilliant idea. :grinning:

I'll go with that as it will make wiring up much easier.

Thanks,

Martin