I am using an Arduino Due to temporarily control a tensile testing frame. The motor is driven by an Advanced Motion Controls 20a14 Analog Servo Drive (http://www.a-m-c.com/download/datasheet/20a14.pdf
). From what I gather from the datasheet, the +REF and -REF voltage input with respect to REF ground proportionally controls the current going to the motor. So I wrote some code to use a joystick to control the DACs on the due, buffered them through an op amp, then connected the first DAC to the +REF and the second DAC to the -REF and the REF ground to the Arduino ground.
When nothing is connected, an oscilloscope shows that the voltage reading from +REF to -REF coming out of the op amp ranges from +3.3v to -3.3v, depending on the position of the joystick. However when I connect the buffer to the Servo Drive, the motors randomly speed up and slow down with little regard to my input with the joystick. An oscilloscope reading from +REF to -REF shows the voltage is randomly fluctuating.
Any ideas on how I can rectify this? I can provide code and/or circuit diagrams (if needed) once I get back to my apartment after the holiday weekend.