Vigyan Prasar: Scientific experiments using a PC

Introduction

Scientific experiments using a PC is a part of VP’s training program designed for the school students. Any student visualizes a PC as an upgraded typewriter or a device like television with Internet access. They also do little bit of programming without knowing how that is useful! They know that computers are used to navigate space shuttles or control sophisticated machines. However, most of them do not have any clue how it is possible and think those must be different computers! Scientific Experiments using a PC is an effort to explain the students how computer is useful to measure and control physical parameters and controls a process.

Scientific Experiments using PC is a software and hardware interface designed, developed and disseminated by Vigyan Prasar. It is an effort to help students to undertake projects using a computer. With it, not only they can measure common physical parameters like temperature, luminosity of light etc. but also control parameters so that it remains within the preset value.

Interestingly, for doing all these things, one need not be computer expert! Any 10th standard student with some knowledge of computer operation should be able to do all the experiments. One can also add new experiments with very little change in the software.

Experiments

Following experiments can be done with the present set up:
1. Experiments on Temperature
   1.1 Measuring ambient temperature
    1.2 Measuring and controlling temperature of any process

2. Experiments on Light Intensity
    2.1 Measuring Illuminance of the room (LUX)
    2.2 Measuring and control light intensity of any process

3. Experiments on Humdity
    3.1 Measuring humidity
    3.2 Measuring and controlling humidity of any process

4. Experiments on sound intensity
    4.1 Measuring sound intensity
    4.2 Measuring sound intensity and feedback control

5. Experiment on pH
    5.1 Measuring pH of any liquid

6. Experiments on Pendulum
    6.1 Time period of pendulum
    6.2 Measuring Gravitational Acceleration (g)
    6.3 Length of the pendulum

7. Experiments for measurement of Voltage, Current and Resistance

How to start

Any standard PC can be used for the purpose. Install the software in your PC. Follow simple instructions when installation is in progress. Once software is installed, connect the interface unit to the commonly available Parallel Port (also known as the Line Printer Terminal (LPT) Port) of your PC.

How it works

Any physical stimulus like temperature, sound intensity etc. is first sensed by using suitable sensors. Sensors produce output voltage, which is comparable to the physical stimulus. Output of the sensor is fed into the Analog to Digital Converter (ADC). The output of the ADC is digital, suitable to feed into the computer through LPT.
The digital value thus received is processed by the computer and produces the output. Output are having two forms – first, it displays the value of the physical stimulus in the monitor and second, it sends command as the feedback signal. This feedback signal is able to switch ON/OFF any electronic switch. The second form of output is important for process control. The computer based on comparison between the received value and the preset value generates feedback signal.

Example

Let temperature of a process need to be monitored and well as to be controlled within a preset value. Electrical heater is the temperature source for that process. Temperature sensor will continuously sense temperature and computer will display the value. If the received value is within the preset value, computer will send a 1 (One) – Logical True as feedback signal – thus heater switch will be ON. This closed loop monitoring will continue as long as the monitoring and control of the process is required. The moment received value exceeds the preset value, computer will send 0 (Zero) – Logical False as feedback which may trigger a relay and switch off the heater. Computer will keep on sending 0 as long as the received value exceeds preset value and heater will be switched off. After sometime, eventually received value will be within the preset value and heater will be turned on by receiving 1 as feedback signal.

Figure 1: Block Diagram of Real-time Processing

Interface components

1) ADC : Analog to Digital Converter,

2) Sensors:
    2.1. Temperature sensor: Thermistor (Thermally sensitive resistors) type
    2.2. Light Intensity Sensor: LDR ( Light Dependent Resistors)
    2.3. Sound Intensity Sensor: Microphone
    2.4. Humidity Sensor: Capacitor type – Dielectric of the capacitor changes with humidity –
          thereby changing capacitance
    2.5. pH Sensor: Capacitor type.
    2.6. Opto-coupler: Infra Red Emitter ( Diode/ Transistor) and Receiver    (Transistor)

3) Switching Circuit: Made using transistors and Relay.

Vigyan Prasar organises demostration/workshop on scientific experiments using PC to train students and teachers.
For further detail please contact:

The Director, Vigyan Prasar A-50,Institutional Area, Sector-62 , Noida-201307, U.P, INDIA
E-Mail	:	vbkamble@nic.in or rnath@vigyanprasar.gov.in
Phone	:	0120- 2404431, 0120- 2404434 , 98112 32599 (M)
Fax	:	0120- 2404437