Help Solar powered Neopixel

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Cuzzi23
 
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Joined: Mon Jan 12, 2015 3:25 pm

Help Solar powered Neopixel

Post by Cuzzi23 »

Hi all,
I would like to drive a single neopixel ( or maybe two) with two solar cells like this one: https://www.adafruit.com/products/700
and control it with an Adafruit feather https://www.adafruit.com/products/2829.
Is it possible?
Would anybody be so kind as to offer guidance?
Thanks in advance

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adafruit_support_mike
 
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Joined: Thu Feb 11, 2010 2:51 pm

Re: Help Solar powered Neopixel

Post by adafruit_support_mike »

You'd need a couple of them, and good light.

Each LED in a NeoPixel uses about 20mA, so the maximum load for a single NeoPixel is 60mA. The pin-panels are rated for 40mA under bright sun, so you'd need two of them to meet the maximum load requirements. Very few NeoPixel projects use them at full load, but solar panels usually don't produce their best-case output current. To a first approximation those would cancel each other, and you could expect a couple of the panels to run a NeoPixel without putting too many limits on what you can do with it.

Our Feather boards only draw about 10mA, so running one of those wouldn't be too much of a challenge.

It would be a good idea to add a small LiPo for more efficient use of the solar panel's output though. Even at 50mA to 100mA, a LiPo will store excess charge when it's available, and will release that charge to cover dips in the panel's output.

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Cuzzi23
 
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Joined: Mon Jan 12, 2015 3:25 pm

Re: Help Solar powered Neopixel

Post by Cuzzi23 »

Thanks Mike,
So I could wire two pin-panels in parallel to the V-Bus pin on the Feather
and connect a Lipo battery and also use the mini usb when needed, correct?
Thanks again

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adafruit_support_mike
 
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Re: Help Solar powered Neopixel

Post by adafruit_support_mike »

Generally correct.

If you put the solar panels in parallel, you'll want to connect a diode to each one's output, then connect the diodes to the load. A solar panel's output voltage depends on the amount of light it's getting and some internal factors in the silicon crystals, so the two panels will almost never have the same output voltage. The diodes will keep the one whose voltage is higher from trying to push current backwards through the one whose voltage is lower.

Small-signal diodes like the 1N4148 will work, but you'll lose less voltage if you use Schottky diodes.

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