Digital filament scale with RFID and MQTT (V3)

Digital filament scale with RFID and MQTT

(translated from german)

This filament scale recognizes the filament spool placed on it by the attached RFID tag. This tag contains information about the spool number and its empty weight.

If a spool with an “empty” RFID tag is placed on the scale, it can be written with the necessary data (number and empty weight). The values can be set accordingly in advance on the display.

If a spool with a valid RFID tag is placed on the scale, the RFID tag is read and the empty weight of the spool is taken into account in the weight display.

The “Transfer data” function transmits the information on the spool number, empty weight, and filament weight (total weight minus empty spool weight) to an MQTT server via MQTT.

If there is no spool on the scale or no RFID tag has been detected, the scale can be tared or the calibration value changed in the submenu.

The entire housing consists of several parts and was printed on my Bambu Lab P1S in PLA without support.

I am also providing the FreeCAD file in case anyone wants to make changes to the model. (I am not a FreeCAD specialist, so please bear with me if I have created the model in a way that is perhaps too cumbersome 😉).

 I am also not a professional in Arduino/C/C++ programming, but with a little AI support, I have created a perfectly usable piece of software in version 3 of the filament scale.

I used the following components for the scale (all from Amazon), but the parts are probably available elsewhere as well.

-       1x ESP32-WROOM-32 NodeMCU module with CP2102 (AZDelivery)
-       1x RFID reader RC522 13.56 MHz (AZDelivery)
-       1x 1.3" OLED display I2C SSH1106 chip 126x64 pixels with white characters (AZDelivery)
-       1x 5kg load cell
-       1x 24-bit analog-to-digital converter (HX711)
-       1x KY-040 rotary encoder module 360-degree rotary encoder with push button
-       3x 100nf capacitors (optional, if the KY-040 bounces)
-       1x toggle switch (power on/off) 7mm hole
-       1x USB-A built-in socket
-       4x M3x8 (front panel)
-       4x Threaded Inserts M3 (front panel)
-       10x M2x6 (for RFID reader, HX711, OLED display)
-       6x Threaded Inserts M2 (for RFID reader and HX711 A/D converter)
-       2x M5x20 (for load cell lower mounting)
-       2x M4x20 (for load cell upper mounting)
-       100 RFID NFC stickers MF Classic 1 K tags 13.56 MHz ISO 14443 A labels 25mm 

Have fun trying it out for yourself!

PS:

• Changes to the 3D model between versions 1 and 3 were made only to the front panel.
• Description with circuit diagram, Arduino program, and display/menu functions can be found in the attached ZIP file.