M.E. 401 – Mechatronics
Laboratory Four
Waveform Generation and Analysis, Fourier
Seires
Required Materials
Hardware
P.C.
Multi-Function data acquisition board
Speaker and Microphone
Software
Measurement and Automation eXplorer (MAX)
LabVIEW
Study Material
Course Text
LabVIEW Manual
Purpose
Be able to generate a certain functions. Understand Fourier Seires. Generate sine and
square waveforms and observe their frequency spectrums. Understand FFT and how it
transfers time domain to frequency domain
Introduction
We will generate square and sine waves in the time domain. During this process, we will
use a FFT to transform the wave form from the time domain to the frequency domain.
We will represent the signals in terms of its frequency and its amplitude.
Any waveform can be analyzed in terms of the harmonics that compose the signal. We
will use harmonic analysis (also called Fourier analysis) to break down a signal into its
harmonics and analyze the signal.
Part1. Waveform Generation
Sine Wave Generation
1 Create a new VI with an On-Off switch.
1. Configure an analog output channel
a. Create an Analog Channel as in lab 1 using DAQmx Create Virtual
Channel.vi and place on the left side of the block diagram.
b. Add a control to select the appropriate line you want to control.
c. Add a constant for the min and max values. Set to 0 and 5.
Move to the Block Diagram and configure the internal components of your
VI.
2. Create Case Structure
a. Right Click in the block diagram to bring up the Functions Panel, and
select Case Structure from the Structures subpalette. Click and drag
cursor in the block diagram to place and size the structure. (Create Virtual
Channel and Boolean Control should be outside and to the left of your
case structure)
b. Wire the Boolean Control to the Case Structure by attaching the T/Fbox to
the case selector
located on the case structure frame.
c. Configure the Case Structure
i. Inside the True frame of the case structure, add a Sine wave vi
from the waveform generation from Signal processing subpalette
of the Functions menu.
ii. Now right click on the frequency terminal of sine waveform and
go to create and select control. Notice the changes in front panel.
iii. Follow the same procedure for amplitude and phase terminals on
sine waveform.
iv. Now go to front panel and bring up the control menu by right click.
Go to modern subpalette and select the Waveform Chart from
graphs subpalette. Place the waveform chart by right click on the
front panel.
v. Notice the waveform chart vi. In block diagram. Place it inside the
case structure.
vi. Inside the True Frame, add DAQmx Write. Right Click on the
Arrow, Select Type=>Analog=>Single Channel=>Single
Sample=>DBL.
Your Block Diagram should look something like this so far
While Loop: executing commands until a condition is TRUE. Whe the power to the
instrument is ON (Boolean TRUE) the VI will send a series of pulses to the digitally
connected LED. To accomplish this task, we make use of a While Loop that executes the
commands within its window until a condition is TRUE. The condition we will use is a
certain number of iterations.
3. Configure the While Loop
a. Add a While Loop and place it outside of the Case Structure. The
Boolean Control should be inside the While Loop, but outside the Case
Structure.
4. Now right click on the loop condition and select the create control option.
5. Wire the DAQmx Analog Channel terminals.
a. Wire the Task output from Create Virtual Channel to the input of
DAQmx Write.
b. Wire the Error out from Create Virtual Channel to error in of Sine
waveform .vi. Now wire Error out from Sine waveform .vi to the input
of DAQmx Write.
c. Wire the Signal out from Sine waveform .vi to the data terminal of
DAQmx Write. Also wire the Waveform graph with the wire joining the
signal out of the Sine waveform .vi to the data terminal of DAQmx
Write
d.
Add DAQmx Clear Task.vi to the outside-right of the While Loop in the
Block Diagram. Wire the task and error output of DAQmx Write to
DAQmx Clear Task.
e. Check your work by making sure that there are connection tunnels
passing through each of the While Loop, Case Structure, and
Sequence Structure. The tunnels, or data entry and exit terminals,
on the right-hand side of each structure will have white centers
because the FALSE case has not been wired yet.
f. Toggle case structure to FALSE. Wire Create Virtual Channel task
and error out terminals to Clear Task VIs task and error in terminals by
spanning the empty Case Structure.
You should now be ready to run your program. Set the analog line, frequency, and
amplitude.
Here is an image of Part 1 Front Panel and Block Diagram
 Plot the front panel and block diagram
Part 2. Fourier series
Create a vi that uses three sine waveforms to approximate the square wave. This will be
accomplished through the use of a Fourier series. Any periodic function that is piecewise
continuous can be represented by a Fourier series. We will not discuss the Fourier series
in great detail but note that the Fourier series generally consists of Fourier coefficients
with sine and/or cosine terms. The appropriate form of the Fourier series will be given to
you. Be sure to include the appropriate controls and indicators (charts/graphs – for the
harmonics) to monitor the approximation, and feel free to experiment with the program.
(Hint: Use “add” to add 3 sine waves together with specific freq. and apm. below.)
Sine Wave Information
Sine Wave 1
Sine Wave 2
Sine Wave 3
Frequency
.1591
.4774
.7957
Amplitude
1.27
.4244
.2546
 Plot the front panel and block diagram
 Explain how you simulate a square wave using Fourier series (Hint: In this case ,
we use 3 sine waves.)
Your report should follow the format described below:
1. Lab title
2. Hardware and Software
3. Objective
4. Descriptions of the problems you have experienced and how you solved them
5. Solutions to all the questions (will start with a bullet in the lab transcripts).
Note that brief explanations or descriptions after each plot are required.
6. Plots that need to be printed out (will start with a bullet in lab transcripts)
have to be attached with lab reports. Plots should be created by selecting
“File”-“Print”-“Next”-“icon, description, panel and diagram”-“Print”
options, which will also include your lab records such as time or date, etc.
7. Summary or conclusion