ELEC 242 Lab

Experiment 5.3

Electromechanical Dynamics

Components

We've looked at the step response of the DC motor, both electrical and mechanical, several times in past Labs. Finally we will quantitatively examine the dynamics of this behavior.


Step 1:

 Get two 18 V motors and a strobe test disk from the cart. Press the shaft of each motor half way into the hole on either end of the disk. One of these will be the "motor" and the other will be the "generator".


Step 2:

 Plug a phone plug patch cord into P5 on the interface board and another into P6. Connect the other end of the patch cords to the two motors.

Step 3:

 Ground one side of each motor (pins 35 and 37 on the interface board socket strip). Connect the other terminals of the motors to the scope (pin 34 to CH1 and pin 36 to CH2). Connect the function generator output to pin 34. You should have the following circuit, with on CH1 of the scope and on CH2.


Step 4:

 Set the function generator to produce a 1 Hz square wave. Turn the AMPLITUDE control to maximum.

Step 5:

 Observe the waveforms displayed on the oscilloscope. Do these look like what you have observed in the past?

Step 6:

 Using the technique from Part 2 of Experiment 5.1, measure the time constants of both and .

Step 7:

 Separate the two motors. Measure the time constant of .

Step 8:

 Rejoin the two motors. Disconnect the function generator from the motor (leaving the scope connections connected) and connect it to the input of the motor amplifier your built last week. Connect the output of the motor amplifier to the motor.

Step 9:

 Turn on the power supply and set the function generator output to maximum.

Step 10:

 Measure the time constant of .

Question 4:

 Explain the waveforms you have measured in this experiment. In particular, explain the changes in the time constants when the two motors were separated and when the function generator was replaced with the motor amplifier.