04-05-2024 10:26 AM - edited 04-05-2024 11:04 AM
Hello,
I'm currently working on a project involving the control of a stepper motor via the NI USB 6009 data acquisition device. My goal is to drive the stepper motor using either digital or analog outputs, requiring a pulse frequency in the range of 100 Hz to 1000 Hz for optimal control. I've been implementing the control logic using Python to generate the necessary pulses.
However, I've encountered a limitation where the maximum output frequency I've been able to achieve is only around 500 Hz (even if I set to 2000Hz or above), which is insufficient for the desired performance of my stepper motor. This frequency limit is posing a significant challenge to achieving smooth and precise motor control. I have tried both analog output and digital output. None of them reach the frequency
I'm reaching out to see if anyone has faced a similar issue or has suggestions on how to improve the output frequency using the NI USB 6009 with Python. Any advice on alternative approaches, configuration settings, or optimization techniques that could help bypass this frequency limitation would be greatly appreciated.
Thank you in advance for your insights and help.
import nidaqmx
from nidaqmx.constants import LineGrouping
import time
import threading
def simulate_pwm_on_analog_output(frequency_hz, duty_cycle, channel, high_voltage, duration_sec):
period_sec = 1.0 / frequency_hz
high_time = period_sec * duty_cycle
low_time = period_sec - high_time
with nidaqmx.Task() as task:
# Ensure the high_voltage parameter does not exceed the channel's maximum voltage
task.ao_channels.add_ao_voltage_chan(channel, min_val=0, max_val=5) # Adjust max_val based on your device specifications
end_time = time.time() + duration_sec
while time.time() < end_time:
# Write the high voltage for the high part of the cycle
task.write(high_voltage)
time.sleep(high_time)
# Write 0V for the low part of the cycle
task.write(0)
time.sleep(low_time)
if __name__ == "__main__":
# Configuration
frequency_hz = 1000 # Target frequency
duty_cycle = 0.5 # 50% duty
channel = "Dev1/ao0" # Use an analog output channel
high_voltage = 5 # High voltage level for the PWM signal, adjusted not to exceed device limits
duration_sec = 100 # Duration to run the PWM simulation
pwm_thread = threading.Thread(target=simulate_pwm_on_analog_output, args=(frequency_hz, duty_cycle, channel, high_voltage, duration_sec))
pwm_thread.start()
04-05-2024 06:42 PM
You are using software-timed analog output. Python is an interpreter language and performs 10 times slower than LabVIEW or C programming.
If you want to send PWM of 1kHz, here are a few different options: