Digital Readout for Eureka Mignon Coffee Grinders

Uses 10 turn potentiometer to allow Arduino to know where grind setting is. Allows user to switch easily between different roasts after dialing in without losing grind setting, or swap between different styles of brewing.

Materials:
1 10Turn Potentiometer: https://www.amazon.com/DAOKI-BG-US-1026632-P/dp/B085XCN3GF (note: Amazon sent me a version with larger shaft than requested-- make sure your timing pulley inner diameter fits, or you'll have to drill it out)
Timing Pullies + belt: https://www.amazon.com/Zeberoxyz-Synchronous-Aluminum-Timing-Pulley/dp/B09YYQH1CZ?th=1 (Ideally 3-1 ratio)
OLED screen: https://www.amazon.com/Self-Luminous-Display-Compatible-Arduino-Raspberry/dp/B09JWN8K99
Arduino nano: https://www.amazon.com/AITRIP-Arduino-ATmega328P-Controller-ArduinoIDE/dp/B08C9ZVF51/ref=sr_1_9?crid=1MS9EQFZTHXV3&keywords=arduino+nano&qid=1673797158&s=electronics&sprefix=arduino+nano%2Celectronics%2C144&sr=1-9
M3 heatserts: https://www.amazon.com/AIEX-Printing-Embedment-Automotive-4-6x5-7mm/dp/B09TNK8GD6
Screws M3x6mm
Wire
Double sided tape
USB Power brick & mini USB cable
1/4 inch aluminum rod (optional)

dro_box.stl should be printed with supports. All others print without

To assemble, connect Arduino A1 to pin 2 of potentiometer
Connect pin 1 of potentiometer to Arduino 5V ref
Connect pin 3 of potentiometer to Arduino Gnd

Connect SCL/SCK from display to Arduino A5
Connect SDA from display to Arduino A4
Connect Display power (5V) to Arduino 5V ref
Connect Display gnd to Arduino Gnd

Press heatserts into screw holes of dro_box.stl w/ soldering iron
Press heatserts into screw holes of knobadapter w/ soldering iron

Insert potentiometer, display, and arduino into dro_box.stl. Secure arduino to bottom cover (slot at back of box allows for power over usb) using double sided tape. Secure display to front of box using double sided tape.

Optional: Tap 1/4 inch aluminum rod and drill/tap larger timing pully off center of pulley for handle. Note: This works okay for turning grind adjuster, but I find myself just turning the whole pulley so it's only optional.

Friction fit larger timing pulley onto knob_adapter.stl. Set screws of timing pulley can be loosened to make fit tighter

Friction fit knob_adapter.stl onto eureka mignon dial

Turn potentiometer all the way clockwise. Turn grinder knob until burrs chirp to find true 0. Secure box to grinder using double sided tape in an area that allows belt to be as tight as possible. Potentiometer value 0 should now be the true zero for your machine.

Example code dro.ino can be compiled in Arduino IDE and loaded to bard. Code will "save" (volatile memory only) previous value if unchanged for 15 seconds, and display last 5 values. To compile code, you will need to import the Adafruit SSD1306 library, as well as the ArxContainer library. Arduino is powered off of USB