External Microphone

Hi all – this feels like a basic question, but haven’t found any good examples. My goal is to use sound-based patterns, with the ability to locate the sensor board, or an external microphone, separately from the PixelBlaze.

I have a PixelBlaze Standard XL with a Sensor Board attached by wire.

Path One: mount the sensor board externally, use a long cable to connect it. This has a couple of challenges, namely that there isn’t an obv. easy way to mount/protect the sensor board AND have the microphone exposed. I can come up with a few kludgy ideas, but nothing clean.

Is there a clean way to mount the Sensor Expansion board for use as a microphone?

Path Two: use an electret mic with some sort of amp – possibly this one from Adafruit - Electret Microphone Amplifier - MAX9814 with Auto Gain Control : ID 1713 : $7.95 : Adafruit Industries, Unique & fun DIY electronics and kits – this looks easier to mount into something, but still not finding a simple way to do it. I have a Sparkfun Sound Detector in the ‘parts’ bin – but not sure if this would actually work. https://www.sparkfun.com/products/12642

  • With either of these, where would I connect them? do I “piggyback” on the line in, or use one of the Analog ports? Do I need to alter the code in a pattern to see this?*

Path Three: use conventional audio gear (mic, preamp, etc.) to output audio at line level, and connect that by 1/8 min cable. This works functionally but creates a much bigger footprint than I want.

What kind of line level does that jack want? “consumer” or “pro”?

I don’t have an FDM printer but might have access to one, so custom case printing is an option.

thanks for your thoughts!


Hi Andy -

I think that electret with amp is a viable option to use it with the line in (use the blocking cap they recommend). Be sure to use a shielded cable for your audio signal.

Another option is to purchase another Pixelblaze and use it as a remote sync follower to the “leader” controller that’s connected to the Sensor Board. The one with the sensor board can be located where you want it closer to the audio (as well as it’s within WiFi range), perhaps powered off a simple USB cable or USB power pack. The just-released PB+SB case is a good solution if you can solder the sensor board below the Pixelblaze leader. The case barely attenuates the amplitude of the audio available to the onboard mic, though there may be some new cavity resonance introduced - we haven’t measured it yet.

As you said, a long wire between the controller and sensor board is another option, but you might need RS425 differential transceivers over CAT6 depending on how far away it is. I don’t have good experimental data for how long you can go directly before degrading the 2 Mbps serial connection.

Another option is to use a line-level wireless audio remote link. There are lots of options with various ranges and fidelity. I’ve looked at Alto gear for prosumer stuff, hacked a Shure DSLR mic link, used the audio link from a Rocketfish AV transmitter, used a cheap commercial FM transmitter, toy mic versions of that, and the cheap Bluetooth-receiver-to-line-out adapters if I’m just sending audio from my phone. There are so many options and prices that you’ll need to wade through them yourself.

The line-in jack accepts standard line-in, roughly 1 volt RMS (about 2-3 V peak-to-peak).

All solutions above wouldn’t require any code changes. Scaling a signal to an analog-in probably isn’t worth the fact that you lose the frequency data that many patterns use.