Vigyan Prasar is engaged in the development of
new training modules/methodologies/ equipment/ devices for S&T
communication. Scientific Experiments using Computer is a
novel effort to explain to the students how computer is useful in
measuring and controlling physical parameters and processes. VP has
conducted a number of demonstrations and workshops to explain how
experiments on measuring and controlling parameters like
temperature, intensity of light and sound, humidity etc. could be
taken up to illustrate use of computer in a variety of processes.
one use a computer as a multi-meter? Or say as a thermometer?
Scientific Experiments using Computer is a software
and hardware interface that has been developed by Vigyan
Prasar to do that and much more. Through this interface not
only can one measure common physical parameters like
temperature, light or sound intensity, relative humidity,
etc., using a commonly available computer but also control a
few parameters so that it remains within the set value.
A student usually looks at a computer as an upgraded typewriter or a
device like television with Internet access. School students
of classes V XII write reports, browse the Internet, play
computer games and also do a little bit of programming, often
without knowing how that is useful! All students know that
computer is very powerful it can be used to navigate the
space shuttle, or control sophisticated machines/processes.
However, most of them do not have any idea about how
computers do it.
Controlling any process do require measurement of a few parameters
like temperature, light, humidity, etc., and taking
appropriate measure based on the comparison between the set
value and the measured value. For example, if measured
temperature is more than the set value then a heater can be
turned off. Scientific Experiments using Computer is
an effort to explain to students how a computer is useful in
measuring physical parameters and thereby controlling a
process by feedback mechanism.
How it works
physical stimulus like temperature, sound/light intensity, etc.,
is first sensed by suitable sensors. Sensors produce an output
voltage, which is comparable to a physical stimulus. Output of the
sensor is fed into the Analog-to-Digital Converter (ADC). The
output of the ADC is digital, suitable to be fed into the computer
through a parallel port.
The digital value thus received is processed by the computer, which
produces the output. The output is in two forms first, it
displays the value of the physical stimulus on the computer
screen, and second, it sends command as a feedback signal. This
feedback signal is able to switch ON/OFF an electronic switch. The
second form of output is important for process control. The
computer, based on the comparison between the received value and
the set value, generates this feedback signal.
Let temperature of a process need
to be monitored and to be controlled within a set value. An
electrical heater is the temperature source for the process. Here,
a temperature sensor continuously senses the temperature and the
computer displays the value. If the received value is within the
set value, the computer will send a 0 (Zero) Logical False
as feedback signal, and the heater switch will be ON. The moment
the received value exceeds the set value, the computer will send 1
(One) Logical True as feedback, which would trigger a
relay and switch off the heater. The computer will keep on sending
1 as long as the received value exceeds the set value and the
heater would be switched off. After sometime, eventually received
value would be within the set value and the computer would send 0,
which would turn on the heater through the relay. This closed loop
monitoring would continue as long as the monitoring and
controlling of the process is required.
The interface has two components
hardware interface and software interface. Both the interfaces work in
tandem. Hardware interface consists of ADC, electronic switch and
sensors and is connected to computer through standard parallel port.
The interface enables one to read a physical stimulus through sensors,
convert it to digital form before feeding it into the computer and
operate the switching circuit based on the instructions received from
Different sensors are used to sense different stimuli. Sensor converts
the stimulus to a corresponding voltage level. Higher the intensity of
the stimulus, higher is the output voltage generated by the sensor.
However, the relation is not always linear. Non-linearity or
exponential relation between input and the output parameters can be
taken care of at the time of data processing by the computer. The
output voltage is converted to digital form by ADC. One 8-bit ADC is
used in the interface. Any input voltage is converted into a 8-bit
The switching circuit consists of transistors and solid-state relays (SSRs).
Transistors are turned ON or OFF, based on the control bit received
from the computer. The transistors in turn operate the relays. The
relays are connected to external devices, which can be turned ON or
OFF so that the measured value remains within the set value. The SSR
is able to handle high current and voltage so that external devices
like heaters and lamps can be connected to the standard power line
through the relays. Relays are operated by electromagnetic induction.
Therefore, there is no direct contact between the hardware interface
and the external power line (in India standard household supply is 230
volts, 50 Hz).
The software interface is the controlling unit, which processes all
the input data received from the hardware interface. Digital data
(Byte) is compared with the set value and control bit is generated and
sent to the hardware interface to turn ON or OFF the switching
circuit. The user can sit in front of the computer and can control the
entire process by selecting the required sensor and setting the upper
and lower limit of the parameter. Once the parameter is set, the
feedback control continuously receives the data through the hardware
interface and compares it with the set value. This can continue
indefinitely without any human intervention. The software interface
also plots real-time graph and stores all the data in database. These
data can be retrieved any time for possible data analysis.
with the present set up:
Experiments on Temperature
Measuring ambient temperature
Measuring and controlling temperature of any process
Experiments on Light Intensity
Measuring brightness level of a room (LUX)
Measuring and controlling light intensity of any process
Measuring humidity of any place
Measuring and controlling humidity of any process
Experiments on Sound Intensity
Measuring sound intensity
Measuring sound intensity and feedback control
Experiment on pH
Measuring pH of any liquid
Oscilloscope Limited Applications
period/frequency of input waveform
Amplitude of input waveform
Multi-meter Limited Applications
Temperature sensor: Thermistor (Thermally sensitive resistors) type
Light intensity sensor: LDR ( Light Dependent Resistors)
Sound intensity sensor: Microphone
Humidity sensor: Capacitor type Dielectric of the capacitor changes
with humidity, thereby changing capacitance
sensor: Capacitor type.
Opto-coupler: Infrared emitter (Diode/Transistor) and receiver
How to start
Any standard computer can be used for the
purpose. Install the software in the computer. Follow simple
instructions when installation is in progress. Once software is
installed, connect the interface unit to the parallel port [also known
as the line printer terminal (LPT) Port] of the PC. Connect sensors in
the slots provided with the hardware interface.
science students can do physics and computer based experiments using
this interface. As all the measured data is stored, one can analyse
the data for a definite period of time. The interface provides scope
to add new sensors and testing the same.
Till recently computer-controlled
processes were considered to be the area of engineers who use very
sophisticated tools. Scientific Experiments using Computer is
conceptually the same as one visualizes in an industrial process
control. One might not get the highest level of accuracy in
measurement required in a real-life control but one can definitely
get a feel of the same. The main advantage of this interface is the
variety of sensors and different parameters it can read and control.
The interface may be treated as the gateway between the physical world
and computer. Get or derive a new sensor, connect with the hardware
interface and do a new experiment. The types of measurement and
control possible are limited to ones imagination only!
Vigyan Prasar organises demostration/workshop
on scientific experiments using PC to train students and teachers.
For further detail please contact:
Noida-201307, U.P, INDIA
||0120- 2404431, 0120- 2404434 , 98112 32599 (M)