rgresume at gmail.com
Wed Aug 12 10:49:17 CDT 2015
WS2801 & APA102 are easier to control and are more tolerant to timing
issues since they use synchronous signal.
WS2811/WS2812 uses one wire and the timing must be precise.
For through hole applications, I suggest 5mm and 8mm APA-106
5V 4m high density (60+ LEDs/m) strip will require power injection on both
ends (possibly in the middle,) if you plan to light all LEDs at the same
time (due to voltage drop, LEDs farthest from power will turn pink.)
You can also adjust your PS's output to 5.5V, that will help with voltage
drop and may eliminate the need for power injection.
Buy WS2812, not WS2811 strips.
5V versions are better, 12V use resistors to drop voltage or have 3
discrete LEDs connected in series.
BTW, WS2811 pixels are not NeoPixels and I wish people would stop referring
to them as such. NeoPixel is Adafruit's brand name for their PCBs and other
products which incorporate WS2811 pixels. NeoPixel strips are nothing more
than generic WS2811 strips with 400% markup.
On Wed, Aug 12, 2015 at 10:17 AM, Adam Haile via TriEmbed <
triembed at triembed.org> wrote:
> You can absolutely do varying speeds.
> Check out the ColorChase animation here:
> That will run a single pixel down the strip. You can change the speed in
> two ways:
> - Modify the framerate: anim.run(fps=30) #Travel 30 pixels per second
> - Modify the amt parameter: anim.run(amt=2, fps=5) #5 steps per
> second, but light every second pixel
> I would use the first option, since you will light every pixel. You could
> also take the basic code in that animation out and run it manually and then
> specify your own delay between each step. The animation classes are there
> to provide very accurate timing, which you may not need.
> For the LED choice, there are a few things to consider:
> - Price
> - Speed
> - Density
> - Voltage
> NeoPixel (WS281x) and APA102 are the cheapest... NeoPixel is slow and
> APA102 is fast but slightly more expensive. But I don't think you need very
> high speed... APA102 is a better choice for high pixel counts requiring >
> 30FPS. But NeoPixel can keep up at low pixel counts.
> You can also get the typical strips or the "christmas light" style. That
> just depends on the aesthetic you are going for. But the christmas style
> are only generally available in NeoPixel or WS2801.
> Most strips are 5V but 12V is also an option, available in the WS2801 and
> LPD8806 chipsets. But with 12V you generally have a strip where 1 IC
> controls 3 RGB LEDs in series making 3-5" long "pixels", *or* you have
> half ping pong ball sized dome lights with 3-5 RGB LEDs in a cluster making
> one giant round pixel. Given you used to use incandescent lights, I think
> the dome LEDs might just be the ticket for you. Just note that with the
> AllPixel, you don't want to solder on that diode if using 12V. You can, and
> that's why it's there, but if you know you are doing 12V just leave it off.
> Then you can use the barrel jack to power the strip (up to 5A)
> On Wed, Aug 12, 2015 at 9:50 AM, Grawburg via TriEmbed <
> triembed at triembed.org> wrote:
>> Some general questions about the AllPixel.
>> I'm working on an exhibit that could easily use a 4 meter length of LEDs.
>> The exhibit is a racing game for little kids where they pick an
>> animal/insect to see if they can outrun it. (I already have a much larger
>> one that uses a PLC and 48 colored incandescent lights.)
>> Using the Allpixel and a Raspberry Pi can I program the lights to race
>> from start to finish at different rates (presuming, of course, I can write
>> good Python code)?
>> How do I pick the LED strip since there seem to be many choices?
>> What other things do I need to consider?
>> Brian Grawburg
>> Triangle, NC Embedded Computing mailing list
>> TriEmbed at triembed.org
>> TriEmbed web site: http://TriEmbed.org
> Triangle, NC Embedded Computing mailing list
> TriEmbed at triembed.org
> TriEmbed web site: http://TriEmbed.org
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