NeoPixel WS2812 LED strip questions

Projects General Guidance
1

Hi,

I want to use NeoPixel LED strips in my projects, but I am having a hard time getting clear answers from the documentation. The data sheet for WS2812, for example, has some typos. And the documentation lists several conflicting thresholds for supported voltages.

First, what is the minimum voltage to power the LED strip (5V, 3.7V, 4.2V, 6V)?

Do I need a 1000 uF capacitor?

Do I need a resistor for the DIN connection (300 Ohm, 470 Ohm, 500 Ohm)?

Are resistors reversible?

I am interested in controlling the strip from a 3.3V microcontroller without using a leveller. There are reports of this working online, in a few different ways.

Some people describe using the first LED on the strip as a voltage leveler. But doesn't that still require something to level the signal to the first LED?

Some mention a "diode" can be used instead of a leveller. What kind of diode exactly?

If I power an Arduino Pro Mini 3.3V microcontroller with 4.2V to the RAW pin, does that raise the high bit voltage output on the GPIO pins enough to communicate effectively with WS2812 family LED strips without requiring logic level controllers?

The same question asked another way: Is GPIO high bit voltage out constant with respect to the the built-in RAW voltage regulator?

As we raise RAW voltage input, which threshold arrives first: breaking 3.3V communication with peripherals, or smoking the MCU from RAW voltage?

Does the MCU RAW voltage trick work well with other peripherals? Or should I give in and get a leveller?

What kind of leveller exactly for a NeoPixel strip? Because someone online said I was choosing the wrong levellers.

2

-jim lee

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3

Way to go!

Maybe, maybe not. Just use it! Same for the series resistor, connected at the actual input to the strip.

Look, the capacitor is advised if there is a significant distance between the 5 V power supply itself, and the LED strip. Similarly the resistor is advised if there is a significant distance between the microcontroller driver and the LED strip.

What is a significant distance? Well, 5 cm is probably insignificant and a meter probably significant!

And many reports of it not working. :roll_eyes: Use a 74HCT14 with two of its gates cascaded, as a level converter. You can find a use for the other four gates. i will not be drawn into the alternatives.

Just don't use the "Raw" pin. That is always a bad idea. If you are using a Pro Mini 3.3V, it operates perfectly fine from 4.2 V or 5 V. But the WS2812 strip may not work properly at 4.2 V, so you need 5 V.

Are you proposing to operate from a battery? You are going to need a serious battery!

4

OP is trying to make a solar-powered light in a jar.
Several of the answers can already be found in OP's cross-posts.
Leo..

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6

CLOSED AS A CROSS POST

Please do NOT cross post / duplicate as it wastes peoples time and efforts to have more than one post for a single topic.

Continued cross posting could result in a time out from the forum.

Could you also take a few moments to Learn How To Use The Forum.

Other general help and troubleshooting advice can be found here.
It will help you get the best out of the forum in the future.

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