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Neopixels not powering with
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Neopixels not powering with

by 8bitzilla on Fri May 22, 2020 10:03 pm

I am trying to power 37 neopixels and FLORA in a very close proximity with a USB power bank and barrel jack to 2pin JST. I tested each pixel and they are working fine, but once I plug in the power bank I don't get anything. I tried a different power bank and same situation.

Previously, I was using a lipo battery and receiving an error message "Unplug the accessory using too much power to re-enable USB devices," but now I don't get anything at all. A lipo battery would be best, as this is meant to be a wearable, but I can't seem to figure out what the problem is.

Any suggestions on what could be preventing me from powering up? I appreciate your time and support!

8bitzilla
 
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Re: Neopixels not powering with

by dastels on Fri May 22, 2020 11:20 pm

How are you powering the NeoPixels? I.e. what is the power line of the pixel strand/strip connected to?

That error was on your PC? You may have to restart to get the USB back. A typical USB port can only supply 500mA. They get unhappy if you ask for more.

37 NeoPixels, in the worst case (all bright white), will require 2.22A. See https://learn.adafruit.com/adafruit-neopixel-uberguide for all the information on NeoPixels. How much current can your powerbanks provide?

Dave

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Re: Neopixels not powering with

by 8bitzilla on Sat May 23, 2020 5:01 pm

dastels wrote:How are you powering the NeoPixels? I.e. what is the power line of the pixel strand/strip connected to?

I'm sorry, I don't know if you are asking what kind of wire I am using to connect to the FLORA or how the FLORA is connecting to the power source. If its the later, I am using these connectors from the FLORA to the power bank.
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dastels wrote:That error was on your PC? You may have to restart to get the USB back. A typical USB port can only supply 500mA. They get unhappy if you ask for more.

Yes the error was from my macbook, should I try plugging it into a wall or something? I don't know how to do this otherwise.

dastels wrote:How much current can your powerbanks provide?

I was attempting to use a lipo 3.7v @ 2500mAh (https://www.adafruit.com/product/328), but now am using a 5V 2.1A USB power bank. I clearly didn't do the math correctly to get 2.22A as you mentioned. I will get a new one in the meantime.
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I hope this helps, thanks for your support. I am really excited to figure out how to get this powered up!

8bitzilla
 
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Re: Neopixels not powering with

by dastels on Sat May 23, 2020 6:03 pm

2.1A is probably fine unless you have them on all white at high brightness a lot.

What I'm wondering is how you have the neopixels connected to teh Flora.

Each NeoPixel has 3 LEDs, each takes nominally 20mA at full brightness. Hence 37 pixels * 3 LEDs per pixel * 20mA per LED = 2200mA = 2.2A

With the Flora connect3d to the powerbank is there any sign of life? If not, verify the polarity of the JST wiring.

Dave

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Re: Neopixels not powering with

by 8bitzilla on Sun May 24, 2020 3:28 am

Thanks for your help Dave, you're an electric wizard! I would have never checked the JST connecter for polarity (or have known some companies have them swapped). I am so stoked to get back on track with this project, I appreciate your support!
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I have another followup about the level shifter and capacitor for the neopixels from the uber guide:

1. Before connecting NeoPixels to any large power source (DC “wall wart” or even a large battery), add a capacitor (1000 µF, 6.3V or higher) across the + and – terminals as shown above. The capacitor buffers sudden changes in the current drawn by the strip.

Since I am using a power bank, does this still apply? I don't know where the capacitor would go.

2. NeoPixels powered by 5v require a 5V data signal. If using a 3.3V microcontroller you must use a logic level shifter such as a 74AHCT125 or 74HCT245. (If you are powering your NeoPixels with 3.7v like from a LiPoly, a 3.3v data signal is OK)

I managed to power one pixel so far as seen in the image above, so am not sure if this is actually required. I'm also not actually sure where I would attach this to the FLORA. Would it be a problem if I didn't use one?

Thanks again!

8bitzilla
 
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Re: Neopixels not powering with

by dastels on Sun May 24, 2020 11:49 am

Awesome news!

You really have to watch polarities. The Flora power JST has protection against reversed polarity, but not everything do.

Yes, I advise adding a capacitor to the long string of NeoPixels. It would be connected between the power and ground of the NeoPixel string (pay attention to the capacitor polarity). I'm guessing that's the black and red wires in your photo. The purpose is to prevent a sudden surge of current from the power source. Flattening the curve, as it were.

You might be ok without a level shifter. If you start seeing erratic behavior as you add pixels, you'll need one. It's sometimes hit or miss. If you do need one and use https://www.adafruit.com/product/1787 the most basic approach is to use a small perma-proto (https://www.adafruit.com/product/1608) and possibly mount it on the back of the Flora with some double sided foam tape or have it next to it, depending on how you plan to mount things. That would give you a solid way to solder on the NeoPixel wiring. If you wanted to get fancy you could use a JST-3 breakout (https://www.adafruit.com/product/2566) to make the NeoPixels pluginable.

Vbatt should be used to power the NeoPixels. That lets their power also be controlled by the on/off switch. It looks like the power switch FET can handle the demands of the number of NeoPixels you'll have.

Dave

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Re: Neopixels not powering with

by 8bitzilla on Sun May 24, 2020 7:35 pm

Thanks again for the help Dave, I have to clarify a question I have about the capacitor.

dastels wrote: Yes, I advise adding a capacitor to the long string of NeoPixels. It would be connected between the power and ground of the NeoPixel string (pay attention to the capacitor polarity). I'm guessing that's the black and red wires in your photo.

IMG_1149.png
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The capacitor would connect to the red/black wires coming off the FLORA to the first NeoPixels (like the image above) not the JST, correct? I am assuming it would be similar to the way the resistor is added to the dataline to the first NeoPixels.

dastels wrote:Vbatt should be used to power the NeoPixels. That lets their power also be controlled by the on/off switch. It looks like the power switch FET can handle the demands of the number of NeoPixels you'll have.


You gave me a bit more than I asked with the Vbatt point as well, thanks for clarifying so I can actually use the on/off switch!

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Re: Neopixels not powering with

by dastels on Sun May 24, 2020 9:26 pm

You are correct about the placement of the capacitor.

Dave

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Please be positive and constructive with your questions and comments.