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https://github.com/beeb/coffee-scale-app

Firmware and Progressive Web App to connect to a DIY bluetooth enabled coffee and espresso scale.
https://github.com/beeb/coffee-scale-app

coffee coffee-scale esp32 js micropython vuejs

Last synced: 5 days ago
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Firmware and Progressive Web App to connect to a DIY bluetooth enabled coffee and espresso scale.

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README 

        
![alt text](./screenshot.jpg)



# DIY Smart Coffee and Espresso Scale



This project contains all the necessary software to program the

[ESP32 microcontroller](https://learn.sparkfun.com/tutorials/esp32-thing-hookup-guide) and interface with it through a

Bluetooth API-enabled web browser (Chrome, Opera).



The `rs` folder contains the source code for the Rust firmware that need to be flashed onto the ESP32. See the

[README](rs/README.md) for instructions.



The `src` folder contains the source for the Progressive Web App that allows to retrieve the scale's reading in real

time as well as the battery level.



The application is hosted at [coffee.beeb.li](https://coffee.beeb.li) for convenience of users desiring building the

scale.



## Settings



The app works as a timer to achieve the desired extraction in the desired time. A reference curve is displayed, taking

into account the user parameters:



- **Coffee Weight**: how much coffee grounds were put in the basket (the "Read" button puts the current scale value into

  this field)

- **Target Ratio**: the ratio of "coffee out" to "grounds in". The expected output weight is displayed next to the

  field.

- **Pre-infusion Time**: this is an amount of time that is added to the timer as soon as >0.5g are detected in the cup.

  This allows to indicate the desired total brew time including pre-infusion. It's the user responsibility to perform

  the pre-infusion with this amount of time.

- **Total Time**: the total brew time, including any pre-infusion.



## Workflow



- The basket or portafilter is put on the scale and tared with the scale's button.

- The desired amount of coffee grounds is put inside the basket

- the basket or portafilter is put back on the scales, thereby measuring the weight of the coffee grounds

- In the Settings pane, the "Read" button next to the "Coffee Weight" input is clicked to read the current value into it

- The cup is placed on the scale and it is tared with the button

- The "Start recording" button is pressed (only available when the scale reads 0g). The app now waits for an increase in

  weight.

- As soon as the weight exceeds 0.5g, the timer starts counting from the pre-infusion time (default 5s).

- The extraction can be followed in real time and should match the grey reference curve (in a direct drive lever machine

  , the user would adjust the pressure to match the curve)

- When the extraction is finished, the cup is lifted from the scale, thus stopping the recording.



## Features



- Dual-core microcontroller allows for fast sampling rate of the load cell and fast refresh rate of the 128x32 OLED

  display

- Load cell input is filtered with a Kalman filter for fast response and good smoothing

- The weight is communicated through Bluetooth Low Energy every 200ms

- The microcontroller can charge a LiPo or Li-ion battery and report its charge level

- The web-app persists user settings in the browser's local storage

- Can be added to the home screen of smartphones (_e.g._ with Chrome on Android, look almost like a native app)



## Design files



The 3D printable parts are available from the

[prusaprinters page of this project](https://www.prusaprinters.org/prints/36112-diy-bluetooth-coffeeespresso-scale).



## Forked version for ESP32 Feather breakout



User Nkawu forked part of this repo at the following location: https://github.com/Nkawu/coffee-scale-firmware



This alternative version uses a different microcontroller board and doesn't have any power button, as well as two

tactile function buttons.



## Acknowledgments



This project was made possible by the following projects and people (amongst others). Thanks to them!



- [esp-rs](https://github.com/esp-rs/)

- [signalo](https://github.com/signalo/signalo)

- [hx711](https://github.com/DaneSlattery/hx711) by DaneSlattery

- [esp32-nimble](https://github.com/taks/esp32-nimble/) by taks

- [ssd1306](https://github.com/jamwaffles/ssd1306) by jamwawaffles

- [chart.js](https://www.chartjs.org/)



## License



Distributed under the MIT License