Lab 6

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Banana C and D on the breadboard. Attach the mini-hooks to the VCURR+ and AGND test points on the Power Amplifier. Finally, connect the tachometer to Banana A and B using banana leads. 3. Make the following jumpers on the Elvis prototyping board: • DAC0→BNC1+ GND→BNC1- • DAC1→Oscilloscope - Trigger • Banana A→ACH0+ Banana B→ACH0- • Banana C→ACH1+ Banana D→ACH1- Current Sensor Tachometer Elvis BNC 1 Banana C Banana D Banana A Banana B BNC Cable Banana Leads VIN Test Points VCURR AGND Figure 2: Electrical connections. 4. Lock the motor shaft so that you can measure the electrical time constant. Use the screw provided to lock the shaft in place. 5. Create test and triggering waveforms as illustrated below using the Waveform Editor. The triggering waveform will be used to trigger the oscilloscope slightly before the rising-edge on the test waveform, which will be applied to the motor through the power amplifier. The test waveform amplitude is 0.5 V in order to produce a 1 V output from the power amplifier. Triggering waveform, 5V amplitude 1 s a. Open the Arbitrary Waveform Generator SFP in ELVIS, then select the Waveform Editor key and make the following settings on the Waveform Editor: • Units: Hz • Sample Rate: 10000.0 • Segment duration to 2 sec. b. First create a test waveform that has peak amplitude of 0.5V. Select the New Component key to add a component. Make the following settings for this component: • Function Library: Square. • Amplitude: 0.25 V • Offset: 0.25 V 10 Power Amplifier Banana Leads Screw Terminals VOUT AGND Test waveform, 0.2V amplitude t Motor Wires DC Motor Jacks Red Black
• Frequency (Hz): 0.5 c. Click on FILE>>Save As and save the waveform to a waveform data file (.wdt format). d. Repeat for a triggering waveform. Select the New Component key to add a component. Make the following settings for this component: • Function Library: Square • Amplitude: 2.5 V • Offset: 2.5 V • Frequency (Hz): 0.5 • Phase: 4.0 • Duty Cycle (%): 1.0000 e. Click on FILE>>Save As and save the waveform to a waveform data file (.wdt format). 6. You will run three tests of the motor response using input amplitudes of 3V, 4V, and 5V. In the Arbitrary Waveform Generator SFP adjust the update rate to be 10,000 S/s. Load the test waveform into DAC0 and adjust the Gain to 3. Load the trigger waveform into DAC1. Press the Play All soft key. 7. Turn on the Prototyping Board Power and the power amplifier. 8. Start Oscilloscope SFP. Set the source for channel A to ACH1. Select the Display ON softkey. Adjust the timebase to 2 ms/div and set the Vertical Scale to 200 mV/div. Set the trigger source to TRIGGER and the slope to descending. 9. Press the single key and press the log key. Save the data as (.txt). 10. Press the Stop All soft key in the Arbitrary Waveform Generator, increase the gain to 4 and press the play all key then repeat step 11. Adjust the gain to 5 and repeat. 11. Open the 3 files in excel. Convert the current sensor voltage into current in Amperes. Plot the current versus time for the three input voltages on the same plot. Make sure to label your axes. Hand in the plot with your lab write-up. 12. Compute the 63% rise time (τ) and the steady-state current for each plot and record them in the table below. Calculate the armature resistance (Ra) from the steady-state current and the input voltage. Average for the three voltages. Given that τ = La/Ra compute La and average for the 3 voltages. B. Determine the system time constant τ In this part of the lab you will measure the system time constant and use it to calculate the motor’s moment of inertia. 1. Remove the screw and allow the output shaft to rotate freely. 2. Now, you will test the motor time response with three input amplitudes: 4V, 5V, and 6V. Set the DAC0 gain in the Arbitrary Waveform Generator to 4 and press play. 3. View the Oscilloscope SFP in ELVIS. Set the source for channel A to ACH0. Adjust the timebase to 200 ms/div and set the Vertical Scale to 1 V/div. 4. Press the Single key and press the Log key. Save the data as (.txt). 11
Page 1: EME 107B - SPRING 2007 Week of May
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Page 9: Then we can find the motor torque b
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Page 15: C. Measuring the Motor Steady State

Lab 6

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