Neopixels only flashing for a brief second

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

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Neopixels only flashing for a brief second

Post by rel »

I bought some neopixels (low density, 30 leds/meter) and i haven't been able to get them to work. Once the arduino is on, the strip does nothing, but when i connect power to the strip, they leds flash for a brief moment and then turn off. If i strobe the power, the leds will just turn on for a brief second, and then turn on for a brief moment again once i power cycle. I've followed the uberguide both on an arduino uno and with an arduino micro. I'm using 4 rechargable AA batteries (couldn't attach the picture since 3 image maximum) to power the arduino which in turn would power the pixels. I've tried using the battery pack to power both the strip and the arduino, but still the same problem. I cut off the first pixel in the line, still the same issue. Used a 1000uf 16v capacitor along the battery pack, still nothing. I bought the resistor to go across the dataline, nothing. I've resoldered the joins on the pads so that they wouldn't be "cold", nothing.

Sorry that i sound disgruntled but it's pretty frustrating. Any advice would be extremely helpful as my project is hindering on these LEDs.
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Re: Neopixels only flashing for a brief second

Post by adafruit_support_bill »

Can you post an overall shot including the power supply so we can see where all the wires are going?

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Re: Neopixels only flashing for a brief second

Post by rel »

I've kept things "vanilla" in my latest attempt
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Re: Neopixels only flashing for a brief second

Post by adafruit_support_bill »

It looks like you are supplying 4.8v to the VIN pin of the Micro and trying to power the pixels from the 5v pin. The voltage regulator on the Micro needs about 2 volts of headroom to properly regulate, so the minimum voltage for powering it via the VIN pin is 7v. With only 4.8v, the regulator won't regulate.

Fortunately, battery power is pretty stable and 4.8v is close enough to 5v for both the Micro and the Pixels. So you should be able to bypass the regulator and just supply 4.8v to both the 5v pin and the pixels.

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Re: Neopixels only flashing for a brief second

Post by rel »

So what can we chalk this one up to?
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Re: Neopixels only flashing for a brief second

Post by adafruit_support_bill »

Hmmm What kind of rechargeables are those? Most NIMH cells are 1.2v each. They might get as high as 1.4 when fresh from the charger.

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Re: Neopixels only flashing for a brief second

Post by rel »


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Re: Neopixels only flashing for a brief second

Post by adafruit_support_bill »

Check the batteries in your meter. Some meters read high when the batteries start to get low.

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Re: Neopixels only flashing for a brief second

Post by rel »

each battery shows around 1.7-1.8v

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Re: Neopixels only flashing for a brief second

Post by adafruit_support_bill »

What kind of batteries are in the meter?

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Re: Neopixels only flashing for a brief second

Post by rel »

One 9v

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Re: Neopixels only flashing for a brief second

Post by adafruit_support_bill »

Is the 9v battery fresh? As I said earlier, some meters will read too high if the batteries are running low. I don't think it is possible for a NiMH or NiCd rechargeable to put out 1.7v.

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Re: Neopixels only flashing for a brief second

Post by rel »

Changed out the battery in the meter and now i'm reading 5.4v on the entire pack of 4 AA. What should I do now?

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Re: Neopixels only flashing for a brief second

Post by adafruit_support_bill »

5.4v is a little more believable. Have the cells been freshly charged? They usually settle down to 1.2v pretty quickly, but 5.4v is pushing the limit for the Neopixels. They can be damaged by anything more than 5.5v. If you havre a diode handy, you can wire it in series to drop the voltage by about 0.7v as described here http://learn.adafruit.com/battery-power ... rips/diode

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Re: Neopixels only flashing for a brief second

Post by rel »

Got the diode and still getting the same issue. Occasionally they will flash, but nothing else

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