In one of our designs, we used 13 NeoPixels. With none of the NeoPixels "on", the current draw
was about 10 mA. To eliminate this current consumption, from our battery operated Teensy 3 design,
we had to use a 2N3904 NPN driver transistor on the ground return leg. You could have also used a 2N3906 PNP transistor
on the +5 VDC supply. In both cases the 10 ma. current did not disappear due to a "backfeeding return" through
the NeoPixel driver pin from the Teensy 3. We also installed a series diode, with the cathode pointing to the NeoPixel, and with both the diode and the transistor driver fixed the 10 mA. backfeeding problem.
Hope this helps anyone using WS2812 NeoPixels in a battery operated design.
On another design note ... Sparkfun has a sealed 1 meter IP65 waterproof WS2812 NeoPixel strip.
Add a Teensy 3 and some special interface "drivers" and you could have the coolest and best bicycle
night-time lighting and warning indicators. Since the Teensy 3 can now be put to sleep
at around 250 uA then the only design issues would be the 60 mA "off current" of the NeoPixels
and the heavy duty power pack to drive them.
https://www.sparkfun.com/products/12027
was about 10 mA. To eliminate this current consumption, from our battery operated Teensy 3 design,
we had to use a 2N3904 NPN driver transistor on the ground return leg. You could have also used a 2N3906 PNP transistor
on the +5 VDC supply. In both cases the 10 ma. current did not disappear due to a "backfeeding return" through
the NeoPixel driver pin from the Teensy 3. We also installed a series diode, with the cathode pointing to the NeoPixel, and with both the diode and the transistor driver fixed the 10 mA. backfeeding problem.
Hope this helps anyone using WS2812 NeoPixels in a battery operated design.
On another design note ... Sparkfun has a sealed 1 meter IP65 waterproof WS2812 NeoPixel strip.
Add a Teensy 3 and some special interface "drivers" and you could have the coolest and best bicycle
night-time lighting and warning indicators. Since the Teensy 3 can now be put to sleep
at around 250 uA then the only design issues would be the 60 mA "off current" of the NeoPixels
and the heavy duty power pack to drive them.
https://www.sparkfun.com/products/12027
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