# WS2812B issues

• Good point on the data sheet. I guess that makes the most sense. The issue applied on both with USB + battery and just battery pack. The working version does not use pinMode(B15,"af_opendrain").

My programming background is basically VB in HS, some random C/C++/C# and excel macros, so hardly a pro. Just a baseline knowledge to make things happen.

Either way, after overcoming the issue above, I have actually completely finished (the electronics part anyways) my project, and a aside from a brief flash at startup as it conducts onInit() and blacks everything out, which ultimately confirms that its turning on, it works perfectly.

Now for the frigging 100 hours of 3d printing the pieces its going into.

• Mon 2018.08.13

@AdaMan82 to add to what @allObjects points out in above #14, and before your foray into 100+ hours of 3d printing, have you considered the following for the power supply. As you haven't indicated the number of pixels in the strip length, I'm making the following observation based on the following 1 meter strip - Total pixels, 32:

to @Gordon 's point in #15

"You must use a 5V DC power supply to power these strips; do not use
higher than 6V
, or you will destroy the entire strip. Yikes!"

Using four Alkaline batteries might be a bit much (4 x 1.5V =6V), but rechargebles are lesser capacity (4 x 1.2V = 4.8V)

References:
https://en.wikipedia.org/wiki/AA_battery­

https://sciencing.com/energizer-watthour­-battery-specs-7425932.html

http://www.techlib.com/reference/batteri­es.html

E = I x R
volt = current x resistance
P = I x E
watt = amp x volt

So, how many LED's can we safely handle with 4 AA's? How long will those batteries last?

We'll be conservative, pick an easy math value and use 2000mAh at 3.0W
We then may calculate the current at 3.0W / 1.5V = 2A This checks with the datasheet then

We also note that capacity drops as immediate power demands increase.
http://data.energizer.com/pdfs/e91.pdf
I'm seeking a maximum discharge continuous rating suggested, . . . not 'infinite' as some will suggest ;-)

Insert:
Did find this:

Max Discharge Rate 2.0A continuous, 3.0A pulse (2sec on / 8 sec off)

https://www.batteryspace.com/primary-lit­hium-battery-energizer-aa-1-5v-3000mah-u­ltra-capacity-l91vp-non-rechargeable-4-5­wh-2-0a-rate---un-38-3-passed.aspx

A discharge rate of 500mA would provide 4 hrs at 0.75W, which could power 25 LEDs

500mA / 20mA(eaLED) = 25 LEDs

Check: If max cap is 3W then how many 3/4W for how long?

3W / 0.75W/hr = 4hr

Could a battery supply 2A continuous?

2A x 1.5V = 3W

That would be a drain for 100 LEDs at 3W Getting warm, aren't we!

2000mA / 20mA(eaLED) = 100 LEDs

Under ideal conditions at room temperature a single AA cell could power 25 LEDs for four hours.
Note that at least two cells are needed in series to exceed forward voltage drop

This means that, when the LEDs are full on, a four AA cell battery pack could supply 100 LEDs for four hours.

2000mA x 4 x 1.5V = 12W max output

Check: 4 AA x 3W = 12W
Easy analysis shows that this is also 40 LEDs for 10 hr

Then for the Neopixel strip above,
Demand 32 x 20mA = 640mA

2000mA / 640mA = 3.125hr

4 cells x 3.125 = 12.5hr

Check: This is close to our 40 LEDs for 10 hr calculation

The Pico usage is negligible at 32mA/hr
https://www.espruino.com/Power+Consumpti­on

Make sure your conceptual project guidelines allow for this battery holder design before firing up the 3D printer. :-0
Otherwise as allObjects suggests a 5V Regulated supply would be the best alternative. . . .

EDIT:
Thr 2018.08.16
Clarification - The Neopixel calculation above is for a single LED color. When displaying pure white however,

``````require("neopixel").write(B15, [255,255,255]);
``````

all three LED diodes are on, thus trippling the current demand.
Demand 32 x (3 x 20mA) = 1920mA

2000mA / 1920mA = 1.04hr

4 cells x 1.04 = 4.17hr