To control interface is consisting of four main parts: 

• Rotary encoder with push button
• Opto-isolated relay
• 128x32 oled display
• Arduino Nano

The encoder is used to select the different presets. As of now, there are two presets for aeropress and 7 for drip coffee. A curcuit from a mobile charger is providing supply voltage to the arduino from mains. 

I had some problems with noice on the encoder signal. I used two 0.1uf caps and 10k resistors to do a hardware debounce, which worked great. 

I needed to figure out the rate of coffee ground pr second. To do this i simply grind for a specified time interval and measure the mass of ground coffee. Calculating backwards i get a rate of:

Now it is easy to convert the amount of coffee from grams to seconds of grinding. 

Further work: 

• Shrink in size, so it will fit inside the enclosure
• 3D print and enclosure for the display that fits neatly on the outside of the grinder
• Make a fancy splash screen :)