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Gemma M0 Powering Flickering LEDs
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Gemma M0 Powering Flickering LEDs

by sba124 on Wed Nov 11, 2020 5:47 pm

I have been creating these little embroidery/LED constellation pieces and to date have been using the Lilymini protoboard to power them. I use pins 1-4 to power sewable LEDs through PWM to make them flicker like stars. I just went to order some more boards, but Sparkfun is backordered. These boards are also pretty finicky and aren't the most reliable, so I'm looking for something more solid. I started looking into Adafruit's Gemma M0 board as a replacement and was wondering if you could give me some pointers on it. Would I be able to connect about 5-7 LEDs to this board and make them all "flicker" using PWM? If so, how many pins can I use to do this? Would it be possible to connect up to 15 LEDs? For each instance, if they're possible, what battery do you recommend be used to power my piece?

Here's a link to the piece's I've been selling in case you'd like more context: https://www.etsy.com/shop/StarAndStitch

Thank you!:)

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Re: Gemma M0 Powering Flickering LEDs

by adafruit_support_carter on Wed Nov 11, 2020 7:27 pm

In general, it seems like a Gemma M0 and some of these (other colors available):
https://www.adafruit.com/product/1758
would be very similar to your current arrangement.

Here's an example usage:
https://learn.adafruit.com/adafruit-led-sequins

Do you need to control each LED individually?

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Re: Gemma M0 Powering Flickering LEDs

by sba124 on Wed Nov 11, 2020 8:19 pm

Thank you! I would like at least 3 separate pins to control my LEDs so the LEDs are not all flickering in sync.

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Re: Gemma M0 Powering Flickering LEDs

by adafruit_support_carter on Thu Nov 12, 2020 2:20 pm

The Gemma M0 is limited to PWM on 2 of its 3 pins:
https://learn.adafruit.com/adafruit-gem ... -2912362-4
so that may be a limit for your use.

How do you power things with your current setup?

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Re: Gemma M0 Powering Flickering LEDs

by sba124 on Thu Nov 12, 2020 2:33 pm

Okay, that's good to know. I currently use a coin cell CR2032. What is your recommendation for the best way to power the Gemma?

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Re: Gemma M0 Powering Flickering LEDs

by adafruit_support_carter on Thu Nov 12, 2020 2:44 pm

There are various options. See here:
https://learn.adafruit.com/adafruit-gem ... -2912360-2

A single CR2032 may not be enough, but 2x would work:
https://www.adafruit.com/product/783

Just to point out other options that exists - do you know about NeoPixels? Example:
https://www.adafruit.com/product/1260
There's a cost difference. But they would allow you to chain multiple LEDs and control them from a single pin. And as a bonus - RGB color.

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Re: Gemma M0 Powering Flickering LEDs

by sba124 on Thu Nov 12, 2020 4:02 pm

Since the 2x coin cell battery is sold out, what lipoly battery would you recommend? i.e. how much power would you estimate is needed to safely power 5 LEDs and also 15 LEDs?

I have used neopixels before but haven't used them in this project due to their price. Can I make neopixels individually flicker?

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Re: Gemma M0 Powering Flickering LEDs

by adafruit_support_carter on Thu Nov 12, 2020 4:07 pm

Can I make neopixels individually flicker?

You probably could, but it would be worth playing around with some first to make sure you can get exactly what you want. My guess is they would work fine though.

For the LiPos, any would work. The difference would be in how long they would last, with larger capacity LiPos lasting longer.

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Re: Gemma M0 Powering Flickering LEDs

by sba124 on Thu Nov 12, 2020 4:51 pm

Could I use these as a cheaper option with the same ability as the flora neopixel?: https://www.adafruit.com/product/1655

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Re: Gemma M0 Powering Flickering LEDs

by adafruit_support_carter on Thu Nov 12, 2020 5:09 pm

Those are the same thing, just not mounted on a PCB. So you could use the them in the same fashion - but actually attaching to their pins might be a bit tricky. Note the quarter for scale in the product photos. So it's sort of up to your skill / comfort level in dealing with that size of package. It's doable, but definitely not a beginner level thing.

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