Adafruit Neopixels Sound React Circuit Question

[Alysia Dynamik]

Hey Paul -

So I am trying some newish stuff, and I have run into a speedbump, and I'm hoping you can advise me! I recently purchased some Neopixel pieces from Adafruit, with the intention of using the circuit/code from this project: http://learn.adafruit.com/led-ampli-tie/overview in some of my own projects. I was hoping, however, to run off of a Teensy and not have to purchase a Flora.

So! I have the circuit assembled on my breadboard, with a 16-LED ring rather than a chain of individual LED units. I installed the Neopixel Arduino library, ran the strand test, everything seems to be working well. The project code is written for the Flora, but it says that for 5v (or thereabouts) Arduinos, to add in a line of code: "analogReference(EXTERNAL);", and connect the microphone breakout to the ARef pin. So I've done that, and there is some animation, but it's all crazy and not the smooth sound react it's supposed to be.

Well! I think I know what the problem is - the instructions say to connect the mic to the regulated 3.3v pin, rather than regular VCC, to cut down the noise. This seems logical to me... but there is no pin like that on the Teensy 2.0, right?

So here is the question! Do you think I am correct that this is my problem? And, if so, what can I do to modify the Teensy to work with this circuit? I'd really like to get it working well and produce multiple products with the same technology, and I'd rather use Teensies than Floras!

Thanks

 

[PaulStoffregen]

I looked but couldn't find a schematic for this breakout board on Adafruit's site. Is there one? I have a pretty good guess as to what's on that mic breakout board, but without a schematic I am guessing here a bit....

Connecting to the AREF pin probably isn't a good idea. If you use analogReference(EXTERNAL), that pin becomes an input, so it definitely won't work unless you connect the mic board AND some sort of power supply. Can you post a link to the place where that's recommended?

Here's the best way to connect it:


(click for larger)

If noise from the power is a problem, a 100 ohm resistor between VCC on the Teensy and the mic together with a big capacitor from the mic's VCC to GND will help give the mic low-noise power. Connect the capacitor's positive to VCC and negative to GND (forgot to put that on this quick sketch).

If you're powering this from a USB cable and a cheap PC, noise from the USB power might be an issue. Maybe? But even then, I would imagine it should not be a huge problem. If you're powering from a battery or regulated power supply (which isn't running other stuff than the Teensy and this mic), noise on the power line is probably not a problem and it's unlikely you'd need the resistor and capacitor. But they can only help, even if they're overkill.