Build the Circuit

The best way to start is to breadboard first. You can then transfer the circuit to a small perma-proto board when you are satisfied with your circuit and want to consider a permanent mount.

You may solder the headers supplied with Trinket to facilitate breadboarding. A small 3 pin header was placed on the microphone breakout board for breadboard connection. For a more permanent circuit, you could use a servo extension cable to extend the microphone or wire your own three wires from the microphone breakout to the Trinket, power, and ground lines.

The Adafruit Neopixel UberGuide shows the range of Neopixels available for your projects. The single Neopixels pictured have single header pins soldered on. The ring was placed over the middle single LED (pictured on the previous page). If you plan to build a permanent circuit, wiring to the pads would be a better choice.

A good 5 volt power supply is very important if powering more than three Neopixels. You can test the wiring with the USB power, just make sure its plugged directly into the computer USB port or a powered hub, not through the keyboard or monitor. If powering from a wall adapter, anything that can supply 5V and 1A or more should be fine. If you add additional Neopixels, more current may be needed to supply the power they need. Select a power supply (5 volt recommended) that can provide more than your anticipated maximum current. For large power-hungry strips, the Adafruit 5 volt, 4 amp or 10 amp supply could be required, although Trinket can only control approximately 100 pixels (to control more, consider using a larger Arduino with more memory).

Power for the microphone breakout is taken from the Trinket 5 volt regulated power pin. If you have a clean power supply, it can be wired to the 5 volt bus.

Trinket GPIO #2 is both an analog and digital pin. This circuit uses it as Analog Pin 1 to read the varying voltage from the microphone breakout.

Trinket GPIO #0 is used as the digital signal line out to the string of Neopixels.

If you would like to control the brightness of the pixels, you can add a potentiometer (nominal 10 kiloohms, larger than 1k to 1 megaohm should be fine). The center wiper is connected to GPIO #3 (Analog 3 in the Arduino IDE). The changing voltage is read from 0 to 255 which is exactly the range the Neopixel setBrightness function uses to set the pixel brightness. If not used, comment out the value POT_PIN and the code will use maximum brightness. If you have trouble loading programs after adding the potentiometer, temporarily remove it to load the program, then replace.

This leaves GPIO #1 and #4 free for your own use. #1 is also controls the red Trinket LED so it takes some care to use in some applications. #3 and #4 are shared with the USB port, so if you use them, disconnect wiring when programming to avoid signal line interference.

The wiring should also work for Gemma. The brightness control cannot be added to Gemma as pins 3 and 4 are not broken out.
This guide was first published on Oct 11, 2013. It was last updated on Oct 11, 2013. This page (Build the Circuit) was last updated on Sep 08, 2019.