5mm Neopixel jitter

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davidl13
 
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Re: 5mm Neopixel jitter

Post by davidl13 »

The bypass caps are clearly shown in each of the WS2812B, WS2812, and WS2811 Data Sheets. As the WS2811 Data Sheet is linked directly from 1938's product page one would think it would have been the first point of reference. But the library/lab observation is noted once again... ;-)

As the WS2811 Data Sheet also recommends series terms (whereas the WS2812 and WS2812B do not) it'll be "interesting" to see how this goes when a larger number (> 32) of these are strung together with a weak power supply.

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jensa
 
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Re: 5mm Neopixel jitter

Post by jensa »

The caps does the job and they are indeed required. I posted some images at my Tumblr. Really fiddly stuff...
http://jcprojects.tumblr.com/post/10671 ... he-legs-of

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bcochran1
 
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Re: 5mm Neopixel jitter

Post by bcochran1 »

Jens, those pictures are amazing! Your skill with the iron is awesome. Soldering 0603 caps like that makes me shake with fear because I know my hands are unsteady. And you bought 0402 size caps? Those must be like grains of sand. I'd enjoy seeing photos of those, too!

I'm very happy your project is succeeding well. I just purchased a Teensy 3.1 and the Adafruit 5mm diffused NeoPixels, product #1938. I wonder if you could kindly post your code so I can modify it for my tiny NeoPixel project? I'm assuming the Teensy needs special coding conventions.

Happy New Year!

Thanks

Bob


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jensa
 
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Re: 5mm Neopixel jitter

Post by jensa »

Well, yeah. The 0402's were definitely a bummer. We'll see how that goes ;-)

As for Teensy 3.1 and NeoPixels, use the OctoWs library (https://www.pjrc.com/teensy/td_libs_OctoWS2811.html) by Paul Stoffregren and the examples that come with it. It's a great library paired with great hardware, so that a single Teensy can drive 4000+ pixels at rates well above TV refresh rates. Not just that you can even chain them up to make massive displays. They do of course also work great for smaller projects.

Make sure you have a level shifter like the 74LVC245 (https://www.adafruit.com/products/735) as the NeoPixels can't be driven directly. You'll need it to shift the 3.3V output signals of the Teensy to 5V. Enclosed is a pic of how I've assembled mine next to the Teensy. This PCB is connected to an upper PCP that holds a tiny OLED screen and the CC3000 wifi chip.
Teensy, 74LVC245, CC300, 1.3" OLED
Teensy, 74LVC245, CC300, 1.3" OLED
assembly.jpg (129.88 KiB) Viewed 640 times
Happy New 2015!

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bcochran1
 
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Re: 5mm Neopixel jitter

Post by bcochran1 »

Thank you, Jens! I will see if my 74AHCT125 chip can do level shifting duties for the Teensy and the NeoPixels, and I'll try to post some photos over the next few days.

Bob

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bcochran1
 
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Re: 5mm Neopixel jitter

Post by bcochran1 »

I followed your advice and the Teensy with the OctoWS2811 library is great! Initially I want to start with a small project, just to get familiar with another type of NeoPixel and work with it a bit. The 1938 product id is the most labor-intensive of my NeoPixel collection so far. Here is a photo of my progress to date:
teensy_with_adafruit_neopixels_edited_small.jpg
teensy_with_adafruit_neopixels_edited_small.jpg (203.42 KiB) Viewed 614 times
I've stopped at 3 NeoPixels for tonight because I ran out of 0.1 uF capacitors. I will get more tomorrow when my local electronics store opens.

With that said, the 3 pixels are very bright! I will have to bung down the brightness some.

Bob
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jensa
 
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Re: 5mm Neopixel jitter

Post by jensa »

Looking nice! And you have a local electronics store? Lucky you! Last one in my city closed three years ago. Their boss all of a sudden said that they would become an online only store. Really missing to have that and not having to buy online & wait :-/

Since last post I've managed to get the CC3000 stable. It will need to boot every now and then (when it hangs) but it has run happily for many days. I've also picked up my 5V/10A power supply (also from Adafruit https://www.adafruit.com/product/658). Just like @davidl13 suggested - when I added the fourth letter (the M with 21 LEDs), the cheap 2A power supply failed. The addition of 21 new LEDs made voltage fall down to 4.75V and the flicker became uncontrollable.

With the 5V/10A supply, I see no flickering any more. Here's a pic from soldering the M & how the WiFi/MCU assembly looks: https://twitter.com/jenschr/status/550676026771406850

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davidl13
 
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Re: 5mm Neopixel jitter

Post by davidl13 »

Looks very nice and overall I hope you've learned some valuable lessons - a double win!

And now for the obligatory spritz of cold water: how easy do you think it would have been to instead use something like http://www.world-semi.com/en/Lighting/s ... ht_string/ or http://www.world-semi.com/en/Lighting/_ ... string_bo/ ?

We wouldn't have gotten to witness your mad soldering skilz but in general it might have been ever-so-slightly easier!

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bcochran1
 
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Re: 5mm Neopixel jitter

Post by bcochran1 »

This thread is a win for me, too! I too have that same 5v 10A supply, and bought it from Adafruit. If I buy their recommended parts things seem to work. Interesting NeoPixel strings you show there, David! Jens, I wonder about one more thing -- could you post more pictures of your Teensy set up including any project box you will house it with?

Thanks a lot!

Bob

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davidl13
 
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Re: 5mm Neopixel jitter

Post by davidl13 »

Be careful that it's not just the recommended parts - it's the recommended homework, study, design, and applying the lessons from experience (good and especially the bad) that ultimately makes the difference between actually working and maybe-working-if-I-stand-right-here-and-squint-like-this. Kids (of all ages) get into trouble when they believe they can just slap stuff together - far too many "successes" are "temporally constrained". They're actually "new posts for help just waiting to happen", as you see often here when a non-design gets stretched even just a little. The fundamentals do matter, despite the 'duino babies' shiny, glittery, ooo-it's-never-been-done-before! stuff.

That's why I keep pounding the Data Sheet drum with these guys: Data Sheets, even though they sometimes have wildly varying quality, are kinda like the B-i-b-l-e: provided by the creator to help keep you out of the ditch.

Yeah, I thought I saw once that Adafruit actually sold one of those Worldsemi strings that would have been perfect for jensa's project but I can't find it in the store now and guess I just don't remember correctly. Worldsemi has some neat stuff (if marginal Data Sheet quality... ;-) and from the looks of them I believe that Adafruit sources their 30, 60, and 144-length strips (and probably some other stuff I haven't stared at enough) directly from Worldsemi.

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bcochran1
 
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Re: 5mm Neopixel jitter

Post by bcochran1 »

Thank you, David! I know what you mean, and I agree that datasheets are lovely things.

Bob

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chemdoc77
 
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Re: 5mm Neopixel jitter

Post by chemdoc77 »

Hi Davidl13:

The Adafruit product that you are looking for is:

12mm Diffused Thin Digital RGB LED Pixels (Strand of 25) - WS2801 - Product: 322

http://www.adafruit.com/products/322

A previous forum post of mine shows how to mount similar RGB LEDS in a PIR foam board to make a 5X5 matrix.

Best Regards,
Chemdoc77

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davidl13
 
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Re: 5mm Neopixel jitter

Post by davidl13 »

Ah, yes, that's them! Until you look a little closer...it seems that 322 and 738 both are WS2801-based while the links to the ones I showed are both WS2811-based. As they say: subtle, yet subtle... ;-)

It might be nice for Adafruit to do a product retire/refresh/replace with the WS2811-based ones, if only to save young jensa from having to solder 100-something bypass caps! ;-)

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jensa
 
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Re: 5mm Neopixel jitter

Post by jensa »

Hehe. Well @davidl13 I don't mind soldering a few hundred LEDs. It's like meditation to me, much like knitting is to others :-)

As for the pre-made strands, I have one of those (or similar?) and they don't give the look I'm after. The pre-made cables stuck out the back of the letters (too long) and it looked really unprofessional. Another thing was that the "bezel" didn't allow the LED to protrude the inner surface properly like Marquee lights should. It just didn't look good.

As for datasheet - sure. Like I said before - the datasheet still isn't posted for 1938 and they don't contain a ws2811 like Adafruit says. They're based on the PD9823 clone-chip and I mistakenly thought that these came with cap's included. Bummer. But sure - I would have read the datasheet if it was available :-)

This blog entry has a good writeup on the differences:
https://cpldcpu.BANNED.com/2014/06/1 ... 2-clones-/ (It's basically a ws2811 "clone") Like Paul mentioned earlier, the timing is a little different and may need some tweaks.

@bcochran1 Sure. I'm out travelling just now, but I'll post more pictures when I get home. I don't have an enclosure for the electronics yet, but I'll 3D print one as soon I have a 100% stable setup.

The electronics will eventually be hidden behind the letters and I'll model/print a cable-duct-thingie that will also hold the letters in place and lift them up a little. This tiny "lift" will improve the reflection a tiny bit as the letters will be standing on a white, semi-matte surface :-)

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davidl13
 
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Re: 5mm Neopixel jitter

Post by davidl13 »

Interesting. So would you think http://www.world-semi.com/en/Lighting/3 ... ht_source/ might give an "authentic marquee" look?

How about http://www.world-semi.com/en/Lighting/s ... ht_string/ combined with an additional translucent diffusion dome?

Just curious...

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