LED Strip MOSFET?

Hello, I am planning to code my own library to create a sort of spectrum analyzer with extra features. I am going to use LED strips to display the data. I was looking at WS2811 or WS2812 strips (30LEDs/meter), because I've used them before, but does anyone know of a cost effective alternative? I really just need them to be addressable w/ no clock pin, and I don't care if it works with Neopixel.

Anyway, My question is regarding power. For a 12-13m strip, it takes more than the Arduino's 500 mA supply as far as amperage. I know the limit as far as processor memory is 500 LED's (~16'), so I know I'm okay in that department, but it looks like 60mA per trio of LEDs, 30 per meter, for 12m is about 7-8A max. Does this sound correct? Additionally, with such power requirements, will I need a MOSFET chip? I've seen others use them, but I'm not sure if I need one.

nateolson:
it looks like 60mA per trio of LEDs, 30 per meter, for 12m is about 7-8A max. Does this sound correct?

60 x 30 x 12 = 21600

It may not be quite 60 mA, but then again the power supply might also not be quite what it claims, so it’s probably reasonable to use that 21.6 A number.

nateolson:
will I need a MOSFET chip

No. The data line that’s connected to your Arduino is not drawing the 21.6 A. It’s only the power supply current. The current draw on the Arduino pin will be safe. You would only need a mosfet if you wanted to switch the power line. It’s likely the projects you saw using a mosfet were non-addressable LEDs, which were controlled by directly switching the power, rather than by sending data commands to the microprocessors in the addressable LEDs and letting them handle the switching.

Hello

pert:
60 x 30 x 12 = 21600

It may not be quite 60 mA, but then again the power supply might also not be quite what it claims, so it's probably reasonable to use that 21.6 A number.
No. The data line that's connected to your Arduino is not drawing the 21.6 A. It's only the power supply current. The current draw on the Arduino pin will be safe. You would only need a mosfet if you wanted to switch the power line. It's likely the projects you saw using a mosfet were non-addressable LEDs, which were controlled by directly switching the power, rather than by sending data commands to the microprocessors in the addressable LEDs and letting them handle the switching.

It looks like the WS2811 and 2812 actually draw 60mA per three LEDs, meaning 20mA per LED. At 30 LEDs per meter, it looks like it'll draw .6A per meter. I don't think I will need a 21.6A power supply, probably more like 7? Can you confirm this/have you worked with WS strips before?

The "LEDs" in "30 LEDs/m is talking about the RGB grouping. So it's actually 90 individual light emitting diodes per meter (30 red diodes, 30 green diodes, 30 blue diodes). It's standard practice to count RGB LEDs according to their packaged units in this way, rather than referring to the number of light sorces within that package.

nateolson:
have you worked with WS strips before?

Yes. I don't have a huge amount of experience, but I have certainly worked with them.

nateolson:
Hello
It looks like the WS2811 and 2812 actually draw 60mA per three LEDs, meaning 20mA per LED. At 30 LEDs per meter, it looks like it'll draw .6A per meter. I don't think I will need a 21.6A power supply, probably more like 7? Can you confirm this/have you worked with WS strips before?

I did some measurements. I came up with "60 LEDs @ 128 intensity one colour = 390mA" which means, I set for example, only the RED of each pixel, set to half intensity. Breaking that down, each individual LED is drawing 6.5mA. To extrapolate the maximum, all colours (x3) at full intensity (~13mA) = ~40 mA per pixel... 40mA * 60 = 2.4A. That's not a conservative estimation. I think some devices might draw up to 60mA per pixel. That would be 3.6A.

Consider though, if you really intend to operate them at full brightness. They are quite efficient, in a dim room they will leave spots in your eyes even at 10% brightness.

aarg:
I think some devices might draw up to 60mA per pixel.

I linked above to a report from Paul Stoffregen who found 33.5 mA from one sample of WS2812 and 52.5 mA from amother. So your finding certainly doesn't seem to be unusual.

I think when you find the lower price on the addressable LEDs, they are usually the SK6812 clone of the WS2812, even if they are sold as "WS2812". I remember even on Adafruit's website at one time they said that sometimes the NeoPixels they sell are one and sometimes the other (though that was some time ago, so that may not be true for the NeoPixels they are selling at this moment).

Yes, and the SK6812 outperforms the classic WS2812 or WS2812B in that the timing specifications are slightly more relaxed. I suspect that by now, some of the WS2812 from Asia are 100% clones. Also the genuine WS2812 specifications aren't complete. So you should always perform measurements.