Sanity check powering 5 x 12mm Diffused Flat Digital RGB LED

EL Wire/Tape/Panels, LEDs, pixels and strips, LCDs and TFTs, etc products from Adafruit

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PureWeen
 
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Sanity check powering 5 x 12mm Diffused Flat Digital RGB LED

Post by PureWeen »

I bought 5 strands of these for a wearable project
https://www.adafruit.com/products/738

I based my project on this project
https://learn.adafruit.com/flora-brakel ... k/overview

Reading through this
https://learn.adafruit.com/12mm-led-pixels/power
It seems like you'd need a good amount of power for 5 strands....
"a slightly modified ATX computer power supply can provide 30 Amps to power upwards of 500 pixels!"

I'm only using the color green.

Using the sample code to light up all 125 lights it's only drawing about 260 mA's. I used the 3 AA's in series for the power (like the backpack project) and it lasted about 5 hours before they died...

I was pretty surprised that 3xAA's could run that many lights for 5 hours especially since it seems like each pixel should be drawing about 20 mA.

I'm happy about how it's all working out but I'm just trying to understand my numbers and just sanity check if there's something silly I'm missing. Like only using 3xAA's will work fine but they might catch on fire and engulf the wearer in flames.

Thank you in advance

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adafruit_support_bill
 
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Re: Sanity check powering 5 x 12mm Diffused Flat Digital RGB

Post by adafruit_support_bill »

There are a couple factors there that contribute to the current limiting:
With 5 strands wired in series, the resistance of the wire in the strands will add-up.
Alkaline cells have significant internal resistance that increases with current draw, further limiting the current delivered to the leds.

As long as your battery pack is not getting hot to the touch (warm is OK) you should be fine.

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PureWeen
 
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Re: Sanity check powering 5 x 12mm Diffused Flat Digital RGB

Post by PureWeen »

Awesome thanks for the info... It doesn't become warm at all so feeling pretty good about it.

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