This device is designed to plot the relationship between torque and the number of turns in a rubber band. It has been tested using a rubber motor intended for an F1M class model aircraft and can also be used with rubber bands for F1D class models. With some additional adjustments, the device can support experiments on rubber bands of other sizes for educational or research purposes.
The main mechanical components of the device are produced using 3D printing. All necessary parts can be found on Thingiverse, as well as in this repository.
The following components were used to build the electronic circuit of the device:
Controller Nano Atmega 328P
Stepper motor NEMA 17 17HS4023
A4988 Stepper Motor Driver
100 g Load Cell
HX711 Amplifier board
0.96" OLED Display Screen Module 128x64
12 mm Button module
70x50 Prototype Circuit Board
Several photos of the assembled circuit board:
The file torque.ino contains the program used to operate the device. For the sake of brevity, the process of obtaining the calibration factor for the load cell has been omitted (the value used in the code is -7492.035156).
The pcb folder contains the device’s printed circuit board files — thanks to Rick Diaz. It includes both the original KiCad files and the Gerber files. There is also an archive of Gerber files ready to be sent to a PCB manufacturer.