Previously the project plan included adding breadboard mounted potentionmeters and reading their analog signal to set the stepper speeds. This turns out to be a bad approach, as the potentiometers introduce inherent noise, and breadboard mounted components are not resiliant for long term use. Instead, we can interface with the arduino directly from the computer, and set the stepper motor speeds through a homebrewed command line interface (CLI).
| Part | Qty | Price ($) |
|---|---|---|
| Arduino Uno R3 (Atmega328 - assembled) | 1 | 24.95 |
| Adafruit Motor/Stepper/Servo Shield for Arduino v2 Kit - v2.3 | 2 | 39.90 |
| Stepper motor - NEMA-17 size - 200 steps/rev, 12V 350mA | 4 | 56.00 |
| WINOMO Nema 17 Stepper Motor Mounting Bracket w/ M3 Screws 2 Pack | 2 | 16.58 |
| Premium Male/Male Jumper Wires - 40 x 6" (150mm) | 1 | 3.95 |
| Shield stacking headers for Arduino (R3 Compatible) | 2 | 3.90 |
| Switch single pole double throw, breadboard mountable | 2 | ------ |
| Total: | -- | 119.89 |
To use the the Arduino with the command line (CLI) instead of the Java applet, first clone the latest repo (or download the stable source) to some directory:
git clone https://github.com/arduino/Arduino.git
Next, navigate to the library directory:
cd arduino-nightly/libraries
Clone the following three libraries into the library/ directory:
git clone https://github.com/adafruit/AccelStepper.git
git clone https://github.com/adafruit/Adafruit_Motor_Shield_V2_Library.git
Then you can compile, verify, and upload with a single command:
arduino-nightly/arduino --upload main.ino
Note that you may need to allow the current user access to the proper /dev/tty* device as specified by the ~./arduino/preferences.txt or ~./arduino15/preferences.txt file, with the serial.port= parameter.
To view messages printed using Serial.print() in the code, you can open the corresponding tty device with cu. Make sure that the baud rate matches the rate set in setup() using Serial.begin(57600). To exit cu, type ~.. This may end your SSH session if you are programming over SSH, in which case the escape character can also be ~~..
cu -l /dev/ttyACM0 -s 57600
If using a external power source for the stepper motors, you can increase the maximum speed (RPM) of the stepper. Modify arduino-src/hardware/arduino/avr/libraries/Wire/src/utility/twi.h:27:20 to read:
#define TWI_FREQ 400000L