I am trying to control stepper motors for a 3D printer with a RAMPS 1.4 shield connected to an Arduino Mega 2560. I have uploaded Marlin firmware to the board and am currently using Pronterface to test the board's components.
At first, the stepper motors would not move at all when commanded. They would just slightly twitch and them hum, but not rotate. Then, I checked the wiring connections and ensured they were correct, but the problem persisted. Then, I measured the Vref of the stepper drivers, which was 0.79 Volts.
Based on my stepper motors, NEMA 17, the maximum Vref I calculated was 1.36 Volts. After adjusting the potentiometer screw the maximum amount, Vref is 1.19 Volts. Now, the motors WILL rotate when given the 0.1 and 1 command in Pronterface, but return to the twitch and whine behavior when given the 10 or 100 command. What is the cause of this?