Schorschi
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Driving a single WS2811/WS2812 SMD, not a strip

Fri Mar 30, 2018 6:42 pm

Has any one had any success driving a single WS2811/WS2812 SMD LED breakout module? I was able to get a 8 LED bar I already had, to work using rpi_ws281x as available on GitHub. https://github.com/jgarff/rpi_ws281x

But driving a single LED module does not seem to work. I set the number of LEDs to 1, tested with 8 LED bar I already had, only 1 LED lights up. But when I use the single LED breakout module, it does not light up.

I have tried to use the following single WS281x break modules:

The FC-100 type https://www.ebay.com/itm/2811-WS2812-50 ... SwLnBat-ud

And this one, https://www.ebay.com/itm/WS2811-WS2812- ... SwmfhX5uSv

Any help greatly appreciate!

Schorschi
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Re: Driving a single WS2811/WS2812 SMD, not a strip

Sun Apr 15, 2018 10:43 pm

No has ever tried to use these WS2811 based FC-100 modules? Please, anyone, really stuck on how to get these working!

mosespi
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Re: Driving a single WS2811/WS2812 SMD, not a strip

Mon Apr 16, 2018 6:48 am

You power these with 5v and drive them with the Pi GPIO at 3.3v right? If so.. I seem to remember the high/low transition of these modules needs to be a fraction of the input voltage.. and it was really close to not detecting the 3.3v of the Pi as a data 'high'. If that is your problem you were likely pulling down the 5v to something like 4.5v when you were using more modules, at which point the 3.3v of the data line was being 'read' correctly. Does this make sense?

I'm not sure if it will work.. but try one LED with the power and data line driven by 3.3v... or if the module doesn't like that.. drop your 5v to 4.5v or lower for the LED. If it's starts working you know the problem and can come up with a more permanent solution. A regulator would be best or maybe a simple drop resistor might work for testing.

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joan
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Re: Driving a single WS2811/WS2812 SMD, not a strip

Mon Apr 16, 2018 7:10 am

I think you can use an ordinary LED in series on the 5V power line to drop the voltage. Or perhaps I should say diode.

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davidcoton
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Re: Driving a single WS2811/WS2812 SMD, not a strip

Mon Apr 16, 2018 8:20 am

joan wrote:
Mon Apr 16, 2018 7:10 am
I think you can use an ordinary LED in series on the 5V power line to drop the voltage. Or perhaps I should say diode.
Definitely a diode (with a high enough current rating). An LED will drop too much.
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rhildinger
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Re: Driving a single WS2811/WS2812 SMD, not a strip

Mon Apr 16, 2018 2:58 pm

Honestly, if you want these 5V addressable LED's to work reliably and consistently, you're going to have to use a level converter to bump the GPIO output from 3.3V to 5V. It's a pain I know, but every other method is essentially a work around that will work for some LEDs but not for others.

Schorschi
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Re: Driving a single WS2811/WS2812 SMD, not a strip

Sat Apr 21, 2018 2:54 am

I will try driving the control signal at 5v. I have a Arduino UNO Rev3 arriving in a few days, yeah, I know been using Pi for years, well, it was about time to expand my range of controllers. :) Since the Arduino drives logic at 5v, seems perfect time to test this.

The odd thing is, I have an older, about 2 years old strip of 8, that works perfectly with 3.3v logic, and powered at 5v (external). And since it works fine, surprised that the single diode modules don't work with 3.3v logic as well. Will update thread with results once I can test with the Arduino.

Will not be the first time I have had to bump the control logic to 5v using a Pi, if that turns out to be the issue. Also think the timing sensitivity is an issue with these newer components. Should be able determine if that is the issue was well with the Arduino, since it avoids the classic Linux interrupt issue.

Schorschi
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Re: Driving a single WS2811/WS2812 SMD, not a strip

Fri May 04, 2018 4:11 pm

I contacted the vendor to confirm as well, how they did their demo, they used an Arduino. So I grabbed the Adafruit NeoPixel library as well for Arduino. Using my brand new Arduino driving the 8 pixel stick, works with GRB, and 800KHz.

As do the FC-100 labelled single SMD 5050s, I had purchased recently. What is really odd is the very same 8 pixel stick I purchased over a year ago works with 3.3v control logic. But the newer ones single and 8 pixel sticks seem to only like 5v control logic.

I tried again with a Pi, with a voltage leveler to push the control logic to 5v level, but still no success, using a Pi. At least I know the components work, are solder sufficiently to work, so I can focus on the Pi scenario, to resolve it. The Adafruit NeoPixel library for Pi did not work, hence why I think it is now a timing issue on Pi.

Forris
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Re: Driving a single WS2811/WS2812 SMD, not a strip

Fri May 04, 2018 5:11 pm

AIUI the data voltage needs to be at least 70% of the supply voltage.

Try using the control signal straight from the gpio at 3v3, but power the LED using a separate 4v5 (3xAAA batteries) supply. Not forgetting to link the grounds, of course.

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