Electric Motor
==============

In this example code, the motor speed is ramps up for 5 seconds and down for 5 seconds,
as the PWM output is ramped linearly from 0 to 100 % and then back to 0. 


.. code-block:: python

    """ lj_motor.py 

    Uses PWM output to set the speed of DC electric motor.

    This example shows how to use the PWM output to change the speed of a DC motor.
    The PWM output is ramped up to 100% and then back down to 0%.

    Setup:
        You will need:
        - Electric motor (I used a CQRobot DC 6V-183RPM/12V-366RPM)
        - An H-Bridge (I used a DROK L298 Dual H Bridge Motor Speed Controller)
        - A 12V power supply
        Connect DAC0 to the bridge DIR1 (or IN1)
        Connect DAC1 to the bridge DIR2 (or IN2)
        On a U3, connect FIO4 to the bridge PWM IN (or ENA)
        On a U6, connect FIO0 to the bridge PWM IN (or ENA)
        On a T7, connect FIO0 to the bridge PWM IN (or ENA)
        Connect the bridge Vcc and GND to the LabJack VS and GND respectively

    The LabJack methods in this example are:
        set_PWM .......... Sets LabJack configuration for PWM output
        set_dutycycle .... Sets duty cycle of PWM output (-100 to 100)
        close ............ Closes the LabJack device 

    """
    import time
    import numpy as np
    from labjack_unified.utils import plot_line
    from labjack_unified.devices import LabJackU3, LabJackU6, LabJackT7

    # To use a LabJack U6 or a T7, change the device name
    # from LabJackU3 below to either LabJackU6 or LabJackT7
    lj = LabJackU3()

    # Assigning parameters
    tramp = 5 # PWM ramp up/down time (s)
    t = [] # Output time array
    pwm = [] # Output pwm signal array

    # Configuring PWM putput
    lj.set_pwm(dirport1='DAC')

    # Initializing timers and starting main clock
    tcurr = 0
    tstart = time.perf_counter()
    # Executing acquisition loop
    print('Running code for ' + str(2*tramp) + ' seconds ...')
    while tcurr <= 2*tramp:
        # Calculating pwm output
        if tcurr < tramp:
            # Ramping up to 100% for the first `tramp` seconds
            pwmcurr = 100/tramp*tcurr
        else:
            # Ramping down to 0% for the last `tramp` seconds
            pwmcurr = 100-100/tramp*(tcurr-tramp)
        # Updating PWM output
        lj.set_dutycycle(value1=pwmcurr)
        # Updating previous time and getting current time (s)
        tcurr = time.perf_counter() - tstart
        # Appending values to output arrays
        t.append(tcurr)
        pwm.append(pwmcurr)
    lj.set_dutycycle(value1=0)    
    print('Done.')
    # Closing the device
    lj.close()
    del lj

    # Plotting results 
    plot_line([t], [pwm], yname=['PWM Output (%)'])
    plot_line([t[1::]], [1000*np.diff(t)], yname=['Sampling Period (ms)'])