DIY Stepper Drives

Stepper drives can be emulated with available computers and hardware.

Stepper motors require a drive to operate. Different manufacturers offer a variety of costly stepper drives with numerous options. Despite the numbers of additional bells and whistles, drives serve a single essential function: they process a command signal and deliver the proper current and voltage to the stepper motor. This can be emulated with software and other equipment. A programming language such as LabVIEW has the versatility to interface with many devices, including analog signal outputs. Thus, a system already operating such a language can serve as a do-it-yourself stepper drive.

Things You'll Need

• LabVIEW basic software package or other programming language
• PCI slot communications card
• Analog output device
• BNC cable
• Stepper Motor
• Voltmeter or oscilloscope

Instructions

1. Connect the A/D Converter to the computer via the specific unit's instructions. Depending upon the programming language choice, this might require additional hardware. For example, National Instruments offers several cards, which plug into a PC motherboard PCI slot and allow the LabVIEW software to communicate with an analog output device.

2. Develop a simple pulse generation program with the programming language. Programs should command the analog output device to output a signal with the characteristics specified in the motor's documentation. This often requires specific amplitudes, frequencies, polarities or other signal elements. Be sure to include both the forward and reverse direction commands in the program. Test the output with a voltmeter or oscilloscope to verify the signal amplitude, frequency and shape. For example, using the LabVIEW graphical programming language, create a while loop with a start button, a stop button, a switch and the counter/pulse generation and output routines. This should generate a signal with a positive amplitude until the STOP button is depressed. Program the switch to change the amplitude's polarity from positive to negative, thus allowing two-directional movement. Run the program and use a voltmeter to check the voltage outputs.

3. Connect the analog output module to the stepper motor with a BNC cable. Depending upon motor model design, this might require cutting one end of the BNC cable off and soldering stripped signal and ground wires directly to the stepper motor's input terminals/wires.

4. Test the setup by running a series of ten pulses or square waves to the motor. This commands the motor to advance ten steps and then stop. If the motor does not follow this command, then return to Step 2 and adjust the program.

References

• Omega Engineering Technical Reference: Stepper Motors
• National Instruments: ComactDAQ Advisor