SKIN RESPONSE RESISTANCE

METERMINI

BASEDProject

ON

BODY

B.Tech. Report

ANIL KUMAR. ANUSHA SAI. M PMONICA. CH

DEPARTMENT OF BIO-MEDICAL ENGINEERING RANGARAJU INSTITUTE GOKARAJU OFENGINEERING AND (Affiliated to Jawaharlal Nehru Technological TECHNOLOGY University) HYDERABAD 500 090 2010

SKIN RESPONSE RESISTANCE

METER

BASED

ON

BODY

Project Report Submitted in Partial Fulfillment of the Requirements for the Degree of

Bachelor Technologyin BioMedical Engineering b y

of

ANIL KUMAR. 07241A1103) SAI. ANUSHA 07241A1105) CH MONICA. 07241A1117)

M(Roll P(Roll (Roll

No. No. No.

DEPARTMENT OF BIO-MEDICAL ENGINEERING RANGARAJU INSTITUTE GOKARAJU OFENGINEERING AND (Affiliated to Jawaharlal Nehru Technological TECHNOLOGY University) HYDERABAD 500 090 2010

Department of BioMedical Engineering Gokaraju Rangaraju Institute of Engineering and Technology(Affiliated to University)

Hyderabad 500 090 2010

Jawaharlal

Nehru

Technological

Certificat eThis is to certify that this project report SKIN RESPONSE METER BASED ON entitled BODY RESISTANC by ANIL KUMAR. M(Roll No. 07241A1103)ANUSHA SAI. P(Roll E No. 07241A1105)MONICA. CH(Roll No. 07241A1117)submitted in partial fulfillment of the requirements of Bachelor of Technology in BioMedical Engineering of the Jawaharlal for the degree Nehru Technological University, Hyderabad, during the academic year 2010, is a bonafide record of work carried out under our guidance and supervision. The results embodied in this report have not been submitted to any other University or Institution for the award of any degree or diploma. (Guide) Department) B.Balaji Assistant Professor (External Examiner) T.Padma (Head of

ACKNOWLEDGEMEN TThere are many people who have helped us directly or indirectly in the successful completion of our project. We would like to take this opportunity to thank one and all.

First of all we would like to express our deep sense of gratitude towards our project Guide Mr Asst Professor Dept. of BME for always being available whenever Balaji we require her guidance as well as for motivating us through out the project work. We are also grateful to the Mrs , (Head of Dept.of BME for her valuable T.Padma guidance during our project. We would like to express our deep gratitude towards teaching and non-teaching staff for giving their valuable suggestions and co operations for doing our project.

our

Dr. Jandhyala. N. , Principal, Gokaraju Murthy Rangaraju institute of engineering and technology for providing necessary facilities during the execution of this project.

We are also deeply indebted to

We would like to thank all our friends for their help and constructive criticism during our project period. Finally, we are very much indebted to our parents for their moral support and encouragement to achieve higher goals. We have no words to express our gratitude and still we are very thankful to our this world and for every support they gave us. parents who have shown us

Signature Signature Anusha Sai P CH (07241A1105) (07241A1117)

Signature AnilKumar M Monica (07241A1103)

TABLE CONTENTS

OF

1. Abstract 2. Introductio n 3. Principle 4. Circuit Diagram 5. Components 6. Circuit Description 7. Construction 8. Features of IC 9. Applications 10. Advantages 11. Disadvantages 12. Conclusion 13. Scope 14. References

1. Abstract: The skin response meter is a valuable tool which indicates the mental state of a person. The main principle of skin response meter is based on body resistance. It is also called as Gripposcope. Human skin offers some resistance to current and voltage. This resistance changes the state of the body. Mainly they are of 2 states 1. Normal state 2. Stressed state These states are normally indicated by LEDs in the circuit. The leds used are of colors, which has their own prominence. . Red led : It indicates the stress levels of the person.

Actually depending upon the grip of the person the body resistance changes and thus led changes their levels. This circuit is useful to monitor the skin response to the relaxation techniques. It is very sensitive and shows the response during a sudden moment of stress. Even a deep sigh will give response in the circuit. This device is ideal to sense small currents in low input current applications. Thus from this relaxation technique we can observe how much our body is stressed or relaxed.

Skin Response resistance:

Meter

based

on

body

2. Introduction: I. The title means what it says! All muscles are not created equally strong and the conditions that stretch them vary from person to person. II There is really no need of a fight to exhibit your muscular strength. If you feel like rising up . the states, do it with the gripposcope. It makes no doubt in judging your muscular strength. It may you to the lift as quick as your drive thought This testing device isn't for those who can be too touchy! Even a habitual liar will be III . taken by the detective operations of the gripposcope. It can also be used for moisture back a level monitoring or simply for conjuring tricks. IV. It is remarkably simple and portable (pocket-size) device. There are ten LED in an array and of them will be lit showing its eagerness to fight with one you. V. As this project is named as SKIN RESPONSE METER, We eventually need to know about the basics of both skin and body resistances. 2.1 Skin:

The skin is an organ that forms a protective barrier against germs (and other organisms) and the inside of your body inside your body, and keeps what's outside of your body outside. Skin keeps also maintain a constant body temperature. Human skin is only about 0.07 inches (2 mm) helps Skin thick.is made up of two layers that cover a third fatty layer. The outer layer is called the epidermis; it a tough protective layer that contains melanin (which protects against the rays of the sun is and the skin its color). The second layer (located under the epidermis) is called the dermis; gives it contains nerve endings, sweat glands, oil glands, and hair follicles. Under these two skin layers is aatty layer of subcutaneous tissue (the word subcutaneous means "under the f skin"). On average, an adult has from 18-20 square feet (about 2 square meters) of skin, which weighs about 6 pounds (2.7 kg).

2.2 Resistance of Skin: Measurements and research from various sources tell us that 1mA is the sensibility 5mA threshold. to 10mA hurts. 40mA causes heart disturbance. to 100mA is 60mA lethal.These are reactions of a healthy human body. Much lower currents could be lethal for persons with malfunctions, pacemakers or other implanted electronic devices. heart The resistance of human skin is highly variable depending on several different variables, but the two variables are whether the skin is clean or dirty. Clean skin often has a resistance of about main 500 Dirty skin can have electrical resistances of up to several million ohms. ohms.

3. Principle: The skin response meter mainly works on the principle of resistance of body. it also depends on grip of the patient i.e., if the person is stressed, the body resistance decreases, which in the turn leds to glow. Thus by difference in the resistance of the skin this equipment works makes and indicates us by glowing up of leds (green, red).

4. Diagram:

Circuit

5. Components:Resistors: R1 1k R2 1.2k Vr1 220k 1 Vr2 M Semi conductors: IC1 LM3914 speaker D2-D10 red LED

Capacitor: C1 1uf A pair of touch pads Battery 9V : Circuit board.

6. Description:

Circuit

I. The schematic diagram of the gripposcope contains 10 comparators and a linear resistor network. II. It may seem a bitter pill for electronic enthusiasts to wire up 10 op amp comparators and a maze of resistors and LED s. But, long back readymade single - chip devices were made available by electronic part masters, National Semiconductors. III. The eldest of the integrated device, LM 3914, has 11 op-amp block and associated network in a single 18-lead molded chip packed like sardines, (That is nothing. There are more acute cases than this. No less in the other members like 3945 and 3916). IV. Nevertheless, they have extremely low power consumption and a working voltage well below three volts!

6.1 3914:

LM

LM 3914, a monolithic integrated circuit, contains an adjustable reference and a precise 10voltage divider network. A very high input impedance buffer op-amp is placed at the input of step the IC, which is protected against reverse and over-voltage signals. The current consumption is

restricted around 10 mA, even when the LED is lit. A prolonged battery life is guaranteed by setting the device in its dot mode of operation.

6.2 LEDs:

I. The high impedance buffer op-amp ( A1 ) is a voltage follower or a unity gain noninverting amplifier. The output of this stage is an exact reproduction of the input The common mode voltage is definite problem in majority of the voltage voltage. II followers. methods to rectify this is to use a resistor from the non-inverting input One of the . to ground. This resistance provides a path for the input bias current. However, this resistance input impedance of the op-amp. Depending upon the magnitude of sees the resistance non-inverting input and the ground ( RB ), a proportional offset voltage across the is developed across the resistance .

III. This vulnerability of voltage follower is mercilessly exploited in the gripposcope. The resistance of the body acts across the positive input and ground, which changes to aertain extent, depending on the grip on the leads. In absence of body resistance, which c is generally less than 500 K between two palms of a normal person at environmental condition the offset the buffer amplifier will be the ordinary IV. maximum. two fixed points on one body can also act as resistor RB. But this Any other resistance changes drastically if the person is frightened or agitated due to the accompanying change or her skin moisture level. This forms the basis of the basis of the lie in his V. detector. voltage of the buffer amplifier is directly connected to the inverting inputs The output of the comparators. A chain of 1k linear resistors and potentiometer VR1 set the step linearity. Potentiometer VR2 also helps in setting the range of the display. In the absence of body resistance RB across the points X & Y, the offset voltage is maximum. Hence by adjusting VR1 the LED D10 can be made to glow.

6.3 Capacitor:Capacitors are widely used in electronic circuits for blocking direct current while allowing alternate current to pass, in filter networks, for smoothing the output of power supplies, the in resonant circuits that tune radios to particular frequencies and for many other purposes

6.4 Resistors:

Any resistance other than the open resistance across points X & Y will bring the offset down, which in turn makes the lower order LED s to glow. The position of voltage the glowing LED changes proportionally with the changes in resistance across X & Y. The sensitivity & the range of deviation can be potentiometer VR1 & points VR2 by resistor and R1

6.5 Diode:A Zener diodeis a type of diode that permits current not only in the forward direction a normal diode, but also in the reverse direction if the voltage is larger than the like breakdown voltage.

6.6 Battery: An electrical battery is a combination of two or more electrochemical cells used to convert stored chemical energy into electrical energy. A common dry cell battery is the zinc-carbon battery, using a cell sometimes called the dry Leclanche cell, with a nominal of 1.5 volts, the same nominal voltage as the alkaline voltage battery

7. Construction:

I. Construction of the gripposcope is very straightforward as it requires only a few components. possible, use a glass epoxy PCB, which offers comparatively high resistance As far as between connections. A soap box size enclosure will the pin II. do. highly insulated wires, such as multimeter probes, can not act as sensors Special Two vacuum suction type probes are ideal for lie detector type applications. The area of contact between probes and skin plays an important role in varying the resistance between the them. III. The contact resistance of switch S1 should be as small as possible. An important point to keep in mind is that loose & untidy connections may play havoc with the device. IV. After making connections, adjust VR1 in such a way that only D10 is lit. Then adjust VR2 by keeping the probe ends in close contact until LED D1 is lit. A suitable resistor R1 should connected (1K in prototype) at pin 4. If the step linearity is satisfactory with VR1 itself, R1 be canreplaced by a simple wire. Now the instrument is ready to be V. use. obvious reasons a mains derived power supply is not used for the circuit. For Operational is derived from two 1.5 volt batteries. The operation of the device becomes critical voltage if the supply voltage falls below 2.25 volts VI. approximately. Resistor R2 controls the current through each LED. A 1.2 K resistor sets the current to around 1mA through the LED. The power set by the device is well below 40 mW in all the positions.

8. Features of IC: I. Drives LED s, LCD s or vacuum fluorescents II. Bar or dot display mode externally selectable by user III. Expandable to displays of 100 steps IV. Internal voltage reference from 1.2V to V. 12V Operates with single supply of less than 3V Inputs operate down to VI. ground VII. Output current programmable from 2 mA to 30 mA VIII. No multiplex switching or interaction between outputs Input withstands 35V without damage or false IX. X. LED driver outputs are current regulated, openoutputs collectors XI. Outputs can interface with TTL or CMOS logic XII. The internal 10-step divider is floating and can be referenced to a wide range of voltages.

Pin Diagram of IC, LM 3914:

9. Applications: It is used,2) For measuring the electrical resistance of the skin 3) As Lie Detector 4) As Stress level 5) indicator For athletes know the mental state of the 6) To person In the diagnosis of excessive sweating 7) (hyperhydorses)

10. Advantages:I. Sense even smaller currents (10pA) II. Portable III. Low st co IV. Handy V. Low er pow consumption VI. Accurate

11. Di

sadvantages:

I. Exceeding Temperature. II Fatigue . III. Attention IV. Predictability

12. Conclusion: Thus by following the property of resistance, the skin response meter checks out the stress of the patient or levels subject.

14. Scope: Skinresistance meter usingto determine the stress of a person or y response is a model bod a subject. This model can be further developed to design equipments without any errors. It be canused widely in medical fields, forensic departments and in other applications at lower cost.

14. References:Books referred to: 1. Electronic Devices and Circuits , by J.S.beasley, G.Raco. 2. Engineering Analysis 3. Operational Circuits F.Driscoll. T.f.bogart,

Circuit , by William Hayt, Jack E Kemmerly, and Mc Graw Hill. Amplifier and Linear Integrated , by R.F.Coughlin and Fredrick,

4. IEE papers referred to myieee.org E