Brew Command

Difficulty

Beginner

BYOB Kit

$10

Build Time

1 Weekend

Arena

Utility · Demo

Overview

Your morning coffee maker already has a heating element, a pump, and a water reservoir. It just lacks a brain. Wire a relay module to the brew button, connect it to an ESP32, and trigger it from your phone, a schedule, or your morning alarm. The coffee starts before your feet hit the floor.

This build teaches relay control — the fundamental skill behind controlling any high-power appliance with a microcontroller. Same principle powers the Chow Bot, Solar Shade, and half the ambitious builds in the corral.

The Build

You're wiring a relay in parallel with the coffee maker's brew button. When the relay closes, it's electrically identical to pressing the button. The ESP32 controls the relay over WiFi, and you control the ESP32 from anywhere.

Unplug the coffee maker. Remove the bottom panel or back cover to access the control board. Find the brew button — trace its wires to the PCB. You're looking for two solder points or wire connections that the button bridges when pressed.

Take photos before disconnecting anything. Most drip makers have simple momentary switches; Keurigs have more complex logic but the principle is the same — you're simulating a button press.

Solder or clip the wire tap connectors to both sides of the brew switch. Route these two wires out of the case to your relay module. When the relay closes, it completes the same circuit as pressing the button.

Test with a multimeter: touch the two wires together — the coffee maker should start brewing (make sure water and a cup are ready). If it works manually, the relay will work identically.

Connect the relay module's signal pin to GPIO5 on the ESP32. Connect the relay's COM and NO (normally open) terminals to the two wires from the brew switch. Power the relay module from the ESP32's 5V pin.

# ESPHome relay config
switch:
  - platform: gpio
    pin: GPIO5
    name: "Coffee Brew"
    icon: "mdi:coffee"
# ... full config in project files
  

With ESPHome, integrate into Home Assistant for scheduling, or use the built-in time component. Set a daily brew time, link it to your phone's alarm via IFTTT, or trigger it with a voice assistant. The project files include configs for all three approaches.

Add a safety timeout — the relay should disengage after 30 seconds regardless. You're simulating a button press, not holding it down forever.

Secure the relay board inside the 3D-printed enclosure. Mount it to the back of the coffee maker with adhesive strips. Route the USB-C power cable alongside the coffee maker's power cord. Close up the coffee maker case.

Fill the reservoir and load the filter the night before. When your alarm fires in the morning, the coffee is ready by the time you walk to the kitchen.