I’m hacking my coffee maker. I routinely set it up for the morning so that I can just get up and hit the button, but I want to take that further. The goal here is to utilize an ESP8266 to connect to the internet and when given a signal, turn the coffee maker on. The signal can either be Alexa or set to a specific time.
The first step is to figure out how the coffee maker works, and where I run into our first problem. For some reason they used a pair of triangular drive screws?! Who has a triangular screwdriver? But… after some thinking… what’s a hexagon if not a triangle with its corners cut off? And everyone has a set of hex keys! So I got the bottom off after a little fussing.
The next puzzle is to figure out how the existing circuitry controls the coffee maker; the 110V AC wall power is converted to a 5V DC which controls the logic circuitry. The coffee maker does turn itself off when the all the water is gone so an initial “turn on” signal on the 5V line in parallel with the switch should suffice.
Here’s the schematic of the circuit currently functioning on my coffee maker.
Alexa enabled coffee maker circuitry (red=5V, blue=3.3V, black=Gnd made with circuit-diagram.org)
To create our Alexa-controlled switch I can use an ESP8266. These devices connect to WiFi and can be loaded with simple programs called sketches that control, in this case, the HIGH/LOW status of some 3.3V output pins. Since the 3.3V output of the pins is not enough to trigger the 5V switch directly, we use the output pin to control the gate of an N-channel MOSFET. With the drain connected to the coffee’s 5V line and the source to the grounded side of the switch, when the ESP sends the 3.3V signal to the gate the MOSFET conducts and the 5V side of the switch is pulled to ground, triggering the coffee maker. I use a 220Ω series resistor to limit any current spikes when the output pin is triggered, and a 10kΩ resistor to ground so that when not enabled the gate doesn’t float but is pulled to ground.
I had originally planned on powering the ESP directly from the 5V line, but initial testing showed that the ESP drew too much current causing the voltage to drop, preventing the circuit from functioning as intended. It is far less elegant, but I’ll have to power the ESP independently. I already have a micro-usb cable used to load the sketch onto the board, so plugging that into an outlet gives a stable 5V line, and offers an easy way to update or change the sketch on the ESP in the future if necessary. I soldered wires onto the 5V and Ground side of the switch and pulled them out of the coffee maker, connected the circuit as shown in the schematic onto a breadboard, and the circuit was ready to go.
Last thing to put in place was to have the ESP listen for commands from Alexa. For this I use the fauxmoESP.h library. This makes the device discoverable by Alexa by having it mimic a WiFi power plug so Alexa can send it On/Off commands (and nothing more complicated- more on that later). Here’s the sketch I uploaded:
#include <fauxmoESP.h>
#include <ESP8266WiFi.h>
#define WIFI_SSID <wifi network name>
#define WIFI_PASSWORD <wifi password>
#define RELAY_PIN D1 // GPIO pin controlling the MOSFET
fauxmoESP fauxmo;
unsigned long lastTriggerTime = 0;
unsigned long pulseStartTime = 0;
bool pulseActive = false;
const unsigned long cooldownPeriod = 10000; // 10 seconds
const unsigned long pulseDuration = 3000; // pulse duration
void setupWiFi() {
WiFi.mode(WIFI_STA);
WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
Serial.print("Connecting to WiFi");
while (WiFi.status() != WL_CONNECTED) {
Serial.print(".");
delay(500);
}
Serial.println("\nWiFi connected. IP: " + WiFi.localIP().toString());
}
void setup() {
Serial.begin(115200);
pinMode(RELAY_PIN, OUTPUT);
digitalWrite(RELAY_PIN, LOW);
setupWiFi();
fauxmo.createServer(true); // Required for gen3+ Echo devices
fauxmo.setPort(80); // Set to 80 for Echo discovery
fauxmo.enable(true);
fauxmo.addDevice("coffee maker");
fauxmo.onSetState([](unsigned char id, const char *name, bool state, unsigned char value) {
if (strcmp(name, "coffee maker") == 0 && state) {
pulseStartTime = millis();
if (pulseStartTime - lastTriggerTime >= cooldownPeriod) {
Serial.println("Coffee Maker: Triggering HIGH pulse");
digitalWrite(RELAY_PIN, HIGH);
pulseActive = true;
lastTriggerTime = pulseStartTime;
} else {
Serial.println("Coffee Maker: Ignored trigger (cooldown active)");
}
}
});
}
void loop() {
fauxmo.handle();
if (pulseActive) {
if (millis() - pulseStartTime >= pulseDuration) {
digitalWrite(RELAY_PIN, LOW);
pulseActive = false;
}
}
}
When powered, the void setup() sets the relay pin as an output, sets it to low (to ensure the gate is not being triggered), then connects to WiFi. Then fauxmo gets to work creating the device “coffee maker” and setting the “on-state” condition. This is where, when getting the “turn-on” signal from Alexa, I execute a 3 second HIGH pulse to the output pin. I also insituted some code to set a cooldown period of 10 seconds to prevent any multi-trigger events. After loading this sketch onto the ESP and plugging in the external 5V power source, I can talk to Alexa and ask her to discover new devices. She then finds “coffee maker,” after which it appears in my connected devices list (note it shows up as a Royal Phillips Electronics device since it “looks” like a smart home wall plug or bulb because of what fauxmo is doing). Then I can simply ask Alexa to turn on “coffee maker.” Here I took it one simple step further and created a routine, that way I can give it a custom command. In my case, I say “Alexa, make me coffee” and she triggers the ESP and responds “Mmmm… the best part of waking up.”
Prototyped and tested, I can now make coffee from bed! (Provided I’d set it up the night before!) Next up, put all this onto a PCB and hide it internally both to clean up the exterior and prevent spillage onto the electronics.
Also next step: As mentioned, the fauxmo library enables this smart-home automation, but is limited to On/Off commands since we’re emulating a smart wall plug. I’d like to move into using Home Assistant, hosted on something like a Raspberry Pi, as the hub of smart-home devices, then connect the ESP to the hub by installing ESPHome on the ESP board. With this setup, I’d connect any smart devices to the Home Assistant, then manage that online via a dashboard. The plus sides are both that I can connect as many devices in the future as I want without having to connect each of them to Alexa individually, but more importantly because each of those devices can handle much more complex instructions. In the coffee maker’s case, I’d like to make the coffee maker into a true smart device. If I implement a water-level sensor, the coffee maker could receive the turn-on command from the hub, then run logic checks to ensure there’s actually water in the tank- if yes, turn on and have Alexa respond with my Folger’s line, or if not, it could tell the hub there’s no water, and the hub could trigger Alexa to reprimand me for not setting up the coffee the night before! Much more responsive, and a true smart-home device.
But at least for now, I can turn on my coffee maker anywhere in the house that Alexa can hear me!