Low Cost Data Acquisition System for Students

Abstract

Today the engineering education in India is increasing, so the demand of quality projects and quality research at the students level is also increasing. To make good hardware projects most of the time we need to acquire real time data. This acquisition is done through the dedicated device which is called Data Acquisition Device. In India there are very less no. of companies which are making the Data Acquisition Devices and the available devices are very costly for the students. Hence, there is need to provide students a cost effective or low cost device which can suite according to their proposed work. In this paper we have designed and implemented a prototype of Data Acquisition Device (DAQ) using AVR microcontroller. The software for the DAQ device has been mode on MATLAB and LabView and the device has been tested for different tasks and under different conditions.

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International Journal of Electronics Communication and Computer Engineering
Volume 2, Issue 2, ISSN : 2249 –071X
41
Copyright © 2011 IJECCE, All right reserved
Low Cost Data Acquisition System for Students
Sachin Sharma
Instrumentation & Control Engineering
National Institute of Technology, Jalandhar
Jalandhar (144011), India
glasachin@yahoo.co.in
Gaurav Kumar
Instrumentation & Control Engineering
National Institute of Technology, Jalandhar
Jalandhar (144011), India
grvkmr038@gmail.com
Abstract— Today the engineering education in India is
increasing, so the demand of quality projects and quality
research at the students level is also increasing. To make good
hardware projects most of the time we need to acquire real time
data. This acquisition is done through the dedicated device which
is called Data Acquisition Device. In India there are very less no.
of companies which are making the Data Acquisition Devices and
the available devices are very costly for the students. Hence, there
is need to provide students a cost effective or low cost device
which can suite according to their proposed work. In this paper
we have designed and implemented a prototype of Data
Acquisition Device (DAQ) using AVR microcontroller. The
software for the DAQ device has been mode on MATLAB and
LabView and the device has been tested for different tasks and
under different conditions.
Keywords- Data Acquisition Device; MATLAB; LabView; AVR
microcontroller
I. INTRODUCTION
In the present scenario, there is lot of scope of technical
education and many students are also going towards
engineering field. As hardware equipment require a lot of
investment but due to lack of investment colleges are not able
to provide practical oriented education or quality education to
their students which in turns reduce their knowledge about
hardware. This situation creates a big question mark on the
employability of the students as core companies think that
students don’t know anything about the hardware on which
they work and they have to train them before giving them any
project and only on training they have to invest a lot. Hence
there is a big difference between the knowledge of students and
the requirements of the company. This difference arises due to
the high cost of hardware equipments which can be used by
colleges to train the students.
Like any other hardware devices data acquisition device is
also important at college and as well as industry level. DAQ
devices[2-3] are used to send the information from real world
to the computer. DAQ device converts the analog signal and
send it to the computer for the data manipulation. DAQ device
interfaced with good software can show the variation of the
analog quantity with varying parameters. Software can also be
used for implementing any algorithm and this algorithm
together with the suitable hardware device can be used to
implement sophisticated applications. Hence this can be used
for teaching the basic science concepts by showing practically
the variation of any quantity like current variation with voltage,
LDR response, strain gauge response etc. and it can also be
used in various small students’ projects like monitoring and
controlling some physical quantity and an associated process
with that physical parameter. There are lot of DAQ devices
available in the market from different vendors like National
Instruments, Dr DAQ etc. but the cost of these devices varies
starting from 15,000 INR to 3,00,000 INR [1], which can not
be afforded by the students.
The goal of this paper is to provide the basic idea of making
of data acquisition device which can be interfaced easily with
the well-known softwares like Matlab, LabView, and Visual
Basic etc. The proposed DAQ device is very useful for the
application where input signal does not vary rapidly, like
temperature monitoring, level monitoring etc. Hence this
device can easily be used by the college students for their
projects and it also provide a good platform for the students on
which they can see their theory concepts converting into
practical one.
In this paper we have designed and made a data acquisition
device (DAQ) using the AVR atmega 8 microcontroller. This
device sends the digitized information to the computer via
serial communication using RS232 protocol. The software for
the data acquisition is made on Matlab and LabView. We have
tested this device for various applications like temperature
monitoring, level monitoring, LDR response monitoring etc.
under different conditions. The repeatability of the hardware is
also tested and it shows very good results.
II. ARCHITECTURE OF DAQ DEVICE
Data Acquisition Device mainly consists of sample and
hold circuit, digital to analog converter, USART module and a
RS232 connector. Description of every block is given below.
The block diagram of the architecture of DAQ device is
shown in the figure 1. Explanation of each block in the block
diagram is given below.
A. Sample and Hold Circuit
The main function of sample and hold circuit is to sample
the incoming signal. The sampling frequency of the circuit
should be such so that it follows the nyquist criteria of the
sampling theorem.
B. Analog to Digital Converter
Analog to Digital converter is used to convert the analog
voltage into digital sequence. Analog to Digital converter took
the instantaneous voltage value from the sample and hold
circuit and converts it to the appropriate digital sequence

International Journal of Electronics Communication and Computer Engineering
Volume 2, Issue 2, ISSN : 2249 –071X
42
Copyright © 2011 IJECCE, All right reserved
depending the reference voltage. Successive approximation
type A/D converter is widely used in the A/D converter.
Fig.1: Architecture of DAQ Device
C. USART
USART stands for universal synchronous asynchronous
receiver transmitter. It is inbuilt unit under the microcontroller
and it is used to transfer the signal serially to the computer. It
took the digital sequence from the A/D converter and
according the baud rate specification it transfers the data to the
computer.
D. RS232 Connector
RS232 is a protocol which is used to transfer the data
serially between two devices. RS232 connector is used to
connect the RS232 cable to the computer serial port. Output of
the microcontroller USART module connects to the MAX232
IC and output of this IC goes to the RS232 connector.
MAX232 IC is used to make the microcontroller output
compatible to the computer input.
When we connect the RS232 cable to the computer port,
operating system of the computer assigns a port no. to that
port. This port no. is further used in the program to identify
from which port serial data is coming.
The Baud rate of the DAQ device and the computer should
be same otherwise wrong data will be read by the computer.
The implemented DAQ device works on 4800 baud rate. The
same baud rate should be provided in the software.
III. DAQ DEVICE HARDWARE
We made this DAQ hardware on the AVR microcontroller
platform. We use the atmega 8 [4] microcontroller of the AVR
microcontroller series. Technical specifications of the AVR
microcontroller are given below:
 Operating Voltages
o 2.7 - 5.5V (ATmega8L)
o 4.5 - 5.5V (ATmega8)
 Speed Grades
o 0 - 8 MHz (ATmega8L)
o 0 - 16 MHz (ATmega8)
 Power Consumption at 4 Mhz, 3V, 25°C
o Active: 3.6 mA
o Idle Mode: 1.0 mA
o Power-down Mode: 0.5 μA
 Peripheral Features
o 6-channel ADC in PDIP package. Six
Channels 10-bit Accuracy
o Byte-oriented Two-wire Serial Interface
o Programmable Serial USART
 High Endurance Non-volatile Memory segments
o 8K Bytes of In-System Self-programmable
Flash program memory
o 512 Bytes EEPROM
o 1K Byte Internal SRAM
AVR microcontroller comes with on chip analog to digital
converter and on chip USART module. The baud rate of the
USART can be configured by program. For storing the
embedded program it has 8K Bytes of on chip flash program
memory. Hence this microcontroller is a complete system in
itself. We have to just program it according to our requirement.
The following figure shows the prototype hardware which is
made by us.
Fig. 2: DAQ Device hardware
Apart from atmega 8 microcontroller IC there is one more
IC that is MAX232 [5]. Output of the microcontroller is very
low in voltage range. This IC boosts up the microcontroller
signal level so that it becomes compatible to the computer.
IV. SOFTWARE FOR THE DAQ DEVICE
We need a software/program on the computer side to read
and display the data. Any computer language like C, C++, and
Visual basic etc. can be used for this purpose, but the problem

International Journal of Electronics Communication and Computer Engineering
Volume 2, Issue 2, ISSN : 2249 –071X
43
Copyright © 2011 IJECCE, All right reserved
with these languages is they don’t provide enough flexibility to
the programmer as well as to the user. Students will also be not
able to use the data given by the DAQ device for further
application. There are also some power full tools like Matlab
and LabView which provide good user interface and flexibility
for the programmer. Moreover further algorithms can be
implemented with the help of these softwares too. Hence
keeping in mind the requirements of the students we
implemented the software/program for reading and displaying
the data on the computer coming serially from the DAQ device
is made on LabView and Matlab on each.
A. LabView Program
LabView is famous for it’s easy to use graphical interface
and it’s well performance ability to work in real time.
Displaying the data in LabView is also very easy. The read
data from the DAQ device also remain available to the user and
can be used for further manipulation or in other algorithm. The
following figure shows the front panel made for the data
acquisition device.
Fig. 3: Front Panel of the DAQ device program in LabView
The waveform showed in this figure is the response of the
LDR circuit. When light fall on it, resistance will decrease so
the voltage drop across it will also drop. When the light falling
on the LDR decrease the resistance of the LDR [6] will
increase so the voltage drop across LDR will also increase.
This type of waveform as shown in the figure arise due to
rapidly decreasing and increasing the light falling on the LDR.
There are two type of plots in the figure, 1st plot (in green)
is called graph and it plots the accumulated previous data
against the no. of samples. The 2nd plot (black) is called chart
and it plots the instantaneous value of the input on running time
base. From the figure it is evident that the response of labview
is quite good and it provide the best platform for the real time
applications.
In figure, above the graph there are three control buttons
named as: Port number, Baud rate, Error Code. Controls, port
number and baud rate are used to configure the serial port of
the computer. We have made the hardware on 4800 baud rate
so it should be same every time when we use this hardware.
Port no. depends upon the no. provided by the operating system
at the time of connecting the RS232 [7] port to the computer
serial port. In our case it was port 8. Error code occur when
there is misconfiguration in assigning the port no. or in other
cases like serial communication driver of labview is not
installed. Stop button is used to stop acquiring the signal.
B. Matlab Program
Matlab also provide the serial communication interface and
it is widely used tool in academics and in research institutes.
Matlab is used mainly for simulation purpose and it provides
much ease in writing the algorithms. It is a text based
development tool and various complex algorithms can be
written with much ease. Disadvantage of the Matlab is, it
appears to be slow for the real time application, and hence
generally Matlab is not used for the real time applications. The
following program written in Matlab used to configure the
serial port and to display the data.
s=serial('COM9');
set(s,'BaudRate',4800);
fopen(s);
k1=0;
for i=1:1000
a=fread(s,1);
d=a;
for j=1:8
e(j)=rem(d,2);
d=fix(d/2);
end
f=4.5*(e(8)/2+e(7)/4+e(6)/8+e(5)/16+e(4)/32+e(3)/64+e(2)/128+e(1)/256);
pause(.00001);
k1(i)=f;
end
plot(k1);
In this program initially we have configured the serial port
by making it’s baud rate 4800. After reading the digital data
from the serial port we have converted that data into its analog
equivalent voltage value.
Fig. 4 shows the output of the program. Plot shows the
values of the voltages given by the DAQ device serially to the
computer. From the figure is also clear that in Matlab we can
easily convert our digital data into its corresponding analog
value.
In this program too, the read data is available in the array
k1, or its instantaneous value can be taken by doing the minor
modification in the program. This read data can be used further
for any other algorithm or for the decision purpose depending
upon the nature of the application. Matlab data acquisition tool
box can also be used for this purpose [8].

International Journal of Electronics Communication and Computer Engineering
Volume 2, Issue 2, ISSN : 2249 –071X
44
Copyright © 2011 IJECCE, All right reserved
Fig. 4: Matlab response for the same LDR application
V. COST OF THE DAQ DEVICE
This is the important point that what will be the estimated
cost of the proposed prototype of the DAQ device. The total
cost of this prototype is given in the following table.
TABLE 1. Component Price
S.No.
Component Name
Quantity
Cost (INR)
1.
AVR microcontroller
1
100
2.
MAX232IC
1
50
3.
RS232 cable
1
150
4.
RS232 Connector
1
25
5.
PCB
1
500
6.
Other electronics
-
200
Total cost of the prototype is 1025 (INR) which is very less
and it can be afforded by the students for their projects. After
adding various costs and charges it can be available to the
students for just 1500 (INR). This can create a revolution for
the students who wish to go for hardware cum software
projects.
VI. RESULTS
The results of the output of Matlab and Labview have been
shown in Fig. 3 and Fig. 4. These show that the device worked
satisfactory. We acquired the data for long time and it gives
the same results. The repeatability of the hardware is also very
good. We tested this hardware for the various other projects
like temperature and level monitoring. This hardware gives the
same level of satisfactory response for other projects.
VII. CONCLUSION
A low cost data acquisition device has been implemented
and tested under various conditions and for various types of
tasks. Response of the device has been checked for different
application and it gives satisfactory response for all type of
applications. This device can be used for the applications
where input signal is not varying rapidly and very precise
accuracy is not required. Future works include developing a
same low cost device for very precise and fast varying signal
applications so that it can also be applied in biomedical
engineering [9].
REFERENCES
[1] http://www.ni.com/dataacquisition/
[2] http://en.wikipedia.org/wiki/Data_acquisition.
[3] Kalyanramu Vemishetty,” Wireless data acquisition system”, thesis,
submitted in verginia polytechnic institute and state university.
[4] Datasheet of atmel AVR atmega 8 microcontroller.
www.atmel.com/atmel/acrobat/doc2486.pdf.
[5] www.datasheetcatalog.org/datasheet/texasinstruments/max232.pdf,
datasheet of MAX 232 IC.
[6] http://en.wikipedia.org/wiki/LDR.
[7] http://en.wikipedia.org/wiki/RS-232
[8] Brian D. Storen,” Using the Matla b Data Acquisition Toolbox”, tex
paper.
[9] Sten Hansen, Thomas Jordan, Terry Kiper,” Low Cost Data Acquisition
Card for schoolnetwork cosmic Ray Detectors”, Fermi National
Laboratory, Batavia, october 29, 2003.
Authors
Sachin Sharma was born at Dadri, Uttar Pradesh,
India on 5 July, 1987. Currently, He is pursuing his
M.tech degree in Instrumentation and Control
Engineering from NIT Jalandhar. He did his B.tech
in Electronics and Communication Engineering
from GLA Institute of Technology, Mathura. He has
published several papers in International
conferences and International journals. His area of
interest includes signal processing, neural networks,
embedded systems and system designing
Gaurav Kumar was born at Jalalpur village,
Aligarh, U.P., India on 20 May, 1989. He is
pursuing his M.tech degree in Instrumentation
and Control Engineering from NIT Jalandhar. He
did his B.tech in Electronics and Instrumentation
Engineering from Hindustan College of Science
and Technology, Mathura. His area of interest
includes control and automation.