Hamish’s Media Controller

Working on building a small media controller using a rotary encoder and key switches with plans to add rgb indicators. Currently working with a cardboard prototype running a Pro Micro.

Using the following packages in Arduino IDE 1.8.13:

SimpleRotary github
HID-Project arduino reference
NeoPixel arduino reference

Blog

First test

Using an arduino pro micro with a rotary encoder I started playing around with encoder libraries and the HID-Project for volume control. I settled on SimpleRotary for its ease of use and straightforewards debouncing. Pictured below is the micro connected to the rotary encoder on a breadboard.

Prototype 1: Pro Micro and rotary encoder on breadboard Apr 30 2021

Prototype begins

With the basic concept started, I made a base and knob for my enocder out of cardboard with room for two pushbuttons for previous/next track (the end goal would be to replace these with keyswitches).

Prototype 2: Rotary encoder and buttons on cardboard body, cardboard knob

With the controls set up and working to control volume up/down, mute, pause/play, and next/previous track, I worked on the LED lights. I chose some NeoPixel rings with 12 LED’s as they were easily accesible and were the right size. The Adafruit_NeoPixel library let me initialize to a standby colour and react to controls being adjusted. I had originaly hoped to use it to indicate my computers volume, however, this would require setting up code/drivers on my computer to send this information to the micro istelf which I do not currently feel interested in doing.

Figure: Showing Adafruit NeoPixel ring on base with and without knob

Gif: Showing LED ring changing colour under various actions

I also threw in a third button to the Micro’s reset pin for debugging. There is currently a bug where after time has passed, the micro’s communication to the computer slows down to only update about 5 times per second. Opening the serial monitor fixes this, and so does reseting the board. May 04 2021

Making the knob

My next step was to find a satisfying rotary knob of the size I was thinking of (no luck so far) or make my own. So I tried drawing up an idea in AutoCAD that I based on my cardboard prototype. I made the knob have an exterior radius of 26mm, and made sure to include a 6mm diameter hole in the middle. My goal is ultimately to have something made out of metal but for now 3D printing allows for rapid prototyping.

Figure: First CAD drawing of rotary encoder knob. Gif: Printing of the first knob.

The printed knob’s domensions were a little bit off so I used a 15/64 in drill to bring the center hole to the correct size and open the exterior hole wide enough to bring a screwdriver through. This worked very well as a temporary version but turning a screw through the plastic is not a permanent fix. Overall I found this model works very well, the white plastic walls allow more light than I was expecting through. In the meantime I updated some smother colour transitions, added highlights for skipping through tracks, and a green flash for pause and play.

Figure: Photo of both prototype knobs side by side followed by gif showing the LED colours under various actions. May 08 2021

Adding Keyswitches

I ordered some Cherry MX brown switches to take the place of my pushbuttons as I want to feel a little ‘bump’ as I press them. Once soldered they are just as simple as the pushbuttons but much more satisfying. I made a new section of the cardboard prototype to hold the keys at the right height, I plan to replace the bottom-most buttons keycap with a 2u wide one.

Figure: Testing the Cherry MX brown keyswitches and adding them to the prototype.

I am holding off on developing a more solid prototype while I learn how to program an esp32 using the esp-idf. I will transfer this code onto the new device using the built in bluetooth capability instead of a wired connection. I havent decided if I want to add a rechargeable battery or keep it wired. June 11 2021

Hamish Johnson

June 2021