Grind-by-Weight Grinder Plug for ESPHome

An ESPHome-based grind-by-weight controller for espresso grinders using:

• a cheap BLE coffee scale
• an ESP32 smart plug with relay output
• fully local, on-device dosing logic

This project lets you plug your grinder into an ESP32 smart plug, pair it with a BLE scale, and dose by target weight automatically.

• Connects to a BLE coffee scale
• Reads live weight updates
• Starts the grinder relay
• Estimates dispense rate in real time
• Predictively stops the grinder before the target is reached
• Learns grinder delay over time to improve accuracy
• Exposes a built-in local web UI
• Works with or without Home Assistant once flashed

This project was built against this very cheap BLE scale:

• Amazon AU: https://www.amazon.com.au/dp/B0FPQ6G6V1?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_2

At the time of writing it was roughly AUD $20.

This was built for the Athom ESPHome-compatible ESP32-C3 AU plug:

• Athom ESP32-C3 AU plug for ESPHome: https://www.athom.tech/blank-1/esp32-c3-au-plug-for-esphome

This project uses ESPHome as the firmware platform, but the actual grind-by-weight logic runs locally on the device.

That means:

• Home Assistant is optional
• Internet access is not required
• Dosing still works if Home Assistant is down
• The device exposes a built-in web interface via web_server
• BLE handling, relay switching, prediction, and delay learning all happen on-device

So while this is packaged as an ESPHome YAML config, operationally it behaves like a standalone local controller.

• Predictive grind-by-weight dosing
• BLE scale integration
• Optional tare before dose
• Learned grind-delay compensation
• Live dispense-rate estimation
• Physical button actions on the smart plug
• Local web interface
• Home Assistant support if you want it
• Fallback AP for recovery

The controller watches live weight notifications from the BLE scale and estimates current grind rate in grams per second.

While dosing:

1. the grinder relay turns on
2. the device watches the measured weight
3. it estimates the current dispense rate
4. it predicts where the final weight will land after grinder stop lag
5. it turns the grinder off before the target is physically reached
6. after settling, it learns from the final error and adjusts the delay parameter

This makes it much more accurate than a simple timed run.

The plug LED is used as a simple connection indicator:

• solid blue when the scale is connected
• blink pattern when not connected to the scale

This switches mains power to your grinder. Use appropriate caution.

A few notes:

• This config is designed for an Athom plug with the pinout used below
• BLE scale protocols vary; this config is written for the scale linked above - you may be able to change it for (for example) the BooKoo scale, but I haven't tried that.
• It will only work with other BLE scales with modification
• Always test with an empty grinder / safe setup first
• Grinder relay control is local, so treat it like any other mains-powered automation

Flash the YAML to a compatible Athom ESP32-C3 AU plug using ESPHome.

Create secrets for:

• Wi-Fi SSID
• Wi-Fi password
• BLE MAC address of your scale, which you can find with any BLE browser app on your phone. I vaguely suspect it's the same on all MY_SCALE devices, D0:4D:00:4F:FE:1A in my case.

Example:

wifi_ssid: "your-wifi"
wifi_password: "your-password"
my_scale_mac: "D0:4D:00:4F:FE:1A"
fallback_ap_password: "change-me"

After the device joins Wi-Fi, open its local IP or mDNS name in a browser.

The built-in web interface lets you:

• trigger doses
• stop the grinder
• tare the scale
• adjust parameters
• inspect live states

If you use Home Assistant, the device can also integrate through the ESPHome API.

But it is not required for normal operation.

The goal was a very cheap, very practical grind-by-weight setup.

Using:

• a ~$20 BLE scale
• an ESPHome-capable smart plug
• local logic on the microcontroller

…you can get a surprisingly capable dose-by-weight workflow for very little money.

Known working target hardware:

• Athom ESP32-C3 AU plug
• BLE scale linked above
• Works with my Sunbeam grinder with the dose switch bridged out (I used a piece of cardboard jammed into the grind switch!)

Other BLE scales may work if they use the same service/characteristic layout and packet format.

This repo is intentionally kept as a single ESPHome config for simplicity.

The dosing logic includes:

• rate gating
• smoothing
• predictive stop
• adaptive delay learning
• connection watchdog behaviour
• interlocks for invalid start weights

If you want to adapt it for another scale, the main things to change are:

• BLE MAC
• service/characteristic UUIDs
• payload parsing in myscale_grams

I'd welcome a PR that supports more types of bluetooth scale.

MIT.