Audio reactive LED baseball cap
Some disclaimers:
This is not all my own work. The bulk of the code came from the official Adafruit VU Meter Baseball Hat tutorial. It's been modified to add detection for bass frequencies, while ignoring (mostly) mids and highs, allowing for a more "reactive" LED strip. The additional audio processing code came from this project by Joao_Claro. Please check both of them out as they're excellent resources and there was no way this would have worked without them.
The projects above use various Arduino-based controllers, but we're using the Adafruit Gemma M0 platform which requires a bit more setup to make it work with the Arduino editor.
Quick demo
Parts bill
I'm based in the UK, so the links are to a UK-based parts supplier, but you can replace them with Amazon or whatever your preferred vendor is. Obviously, Adafruit sell everything other than baseball caps so that might be a natural choice for US-based folks 🤷♂️
| Amount | Part Name | Link |
|---|---|---|
| 1 | WS2812B NeoPixel Strip (60 or 144/m) | https://shop.pimoroni.com/products/flexible-rgb-led-strip-neopixel-ws2812-sk6812-compatible |
| 1 | Adafruit Gemma M0 | https://shop.pimoroni.com/products/adafruit-gemma-m0-miniature-wearable-electronic-platform |
| 1 | Adafruit MAX4466 Electret Mic Amplifier | https://shop.pimoroni.com/products/adafruit-electret-microphone-amplifier |
| 1 | NeoPixel Jewel (Optional) | https://shop.pimoroni.com/products/adafruit-neopixel-jewel-7-x-ws2812-5050-rgb-led-with-integrated-drivers |
| 1 | LiPo Battery Pack (500-650mAh) | https://shop.pimoroni.com/products/lipo-battery-pack?variant=20429082055 |
| 1 | Baseball Cap | Your favourite baseball cap provider |
LiPo considerations
A standard NeoPixel will draw approximately 60mA at full power with all 3 subpixels running at full brightness. There are 30 pixels in the 144/m strip running across the top of the sun visor, which would result in an 1800mA draw at peak power. However, if you do that, you will straight up blind anyone who is looking at your hat, which is why we're running them at less than 5% of their peak power (about 20mA)
At that output, a 500mAh battery will last you over 20 hours. This is because the pixels are only on when sound is detected, so the total power draw is much lower. A 650mAh cell, like the ones used in RC vehicles is a bit more compact and will give you even more time. You may have to make your own JST connector as RC cells ship with a different type of connector.
Prototyping
While developing, I used a Trinket M0 with its header pins soldered in. Plugged into a breadboard, it was much easier to work out kinks in the circuit and try different options. The Trinket uses the same microcontroller and has the same pins as the Gemma M0, plus some extras, making it ideal for the job.
Arduino setup
This build uses the Adafruit Gemma M0 (docs here) microcontroller. It's a much smaller form factor than the Flora used in the tutorial and is much better suited for wearable applications because of its tiny form factor.
As standard, it comes with firmware that runs CircuitPython, allowing you to quickly write Python code for running your wearables. The downside is that because it's having to run a Python interpreter, the maths involved in processing real-time audio signals makes it absolutely crawl. During initial testing, I found that the refresh rate for the beat detection loop was less than 2/second, which was completely impossible to work with.
This is why this project uses C++ rather than Python. In testing, the C++ version performed ~1000x faster, which is exactly what we need for real-time audio analysis.
Before getting started, be sure to run through the following guides:
Once you've set all that up, you should be able to connect to the Gemma/Trinket and flash your code to the microcontroller.
Be aware that if you ever want to go back to using your Trinket/Gemma with Python, you will need to download and flash the stock firmware to the controller
Wiring
Note: I'm using purple for V++ in order to make this diagram more accessible to colour-blind folks
I've modified the original design for the VU Meter Hat to make it more symmetrical. Instead of the "meter" only running side-to side across the width of the strip, it grows from the center of the hat to the outside edges. As a result, there are two physical NeoPixel strips. However, they are both controlled by the same DATA line, resulting in an identical effect on both. The code below sets how many pixels are on each side of the strip.
#define N_PIXELS 15 // Number of pixels in *ONE* pixel strip.Even though the NeoPixels want about 5V, they will happily run off 3.2V, which is what the 3Vo pin on the Gemma provides. Do not be tempted to use the Vout pad, even though it's connected directly to the battery. Doing so will generate a lot of electrical noise on the common GND line and make your mic's readings worthless.
The Gemma's 3Vo pad provides a much cleaner power supply as it will have been filtered by the Gemma's power delivery circuitry.
All the components can share a single power and ground line without interference.
- Connect the In pin on the Jewel to D2 on the Gemma
- Connect the In pin on each NeoPixel Strip to D0 on the Gemma.
- It is better to run 6 individual cables (3 for each strip) through a slit in the center of the hat than try to bridge the positive and GND pins on the strips. You run less risk of snapping a wire that way.
- Pay attention to the fact that the GND and Vin pads will be reversed on one of the strips.
- Also pay attention to the direction arrows on the strips. They only work one way. If you solder to the wrong end of the strip, you'll get nothing.
- Once you've run all the cables through, you can join them inside the headband wherever feels convenient.
- Connect the OUT pin of the mic to D1 on the Gemma.
- Connect all the GND pads on the Gemma, mic and LEDs together however you like
- Do the same for the positive (VCC/Vin/PWR) pads. Remember to use the 3Vo pad on the Gemma.
Flash the code
Once everything is wired in (test using a breadboard or something similarly non-permanent if unsure), you can connect your Gemma to your computer. If you've set everything up right, you should be able to copy the code from this repository into the Arduino IDE and upload straight to the controller.
Lines 78-79 contain some serial output statements so that you can monitor what's happening. Opening the Serial Plotter in the IDE will give you a real-time chart of how the audio detection is working.
Serial.println(n);
Serial.print(" ");To test it, just play some music and see what happens!
Good luck