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1. Monitoring of psycho-physiological Processes Based on Skin
Conductivity , Heart Rate and Skin Temperature
Abstract— Happens to humans a lot of psychological
changes resulting from exposure to situations get him daily or
as a result of the actions that carried out by his activity and
his thinking, andthese changes are known as "stress".
Human exposed to the stress, making the nerve impulses
carrying sense to stimulate many glands, including the sweat
glands in the skin layers, causing an increase in secretions of
these glands of sweat that reaches the skin surface through
ducts , influenced by the conductivity of the skin because of
sweat. In addition; many vital signs affected by the secretions
of various glands throughout the body resulting from
psychological status, such as increased heart rate and skin
temperature.
The idea of this project is to design a device that has the
ability to measure various physiological signals, which are
closely linked with symptoms of stress, such as Galvanic Skin
Response (GSR), Heart Rate (HR), and Skin Temperature
(SKT), are measured by different types of medical sensor
equipment and process by Arduino Microcontroller.
Environmental variables and psychological measured
will be made to the microcontroller, such as a microcontroller
(Arduino) for the purpose of data processing, and then take
deliberate and targeted samples for tests and taking different
values and analyzed for "specific stress range" in each case
to facilitate the diagnosis inthe future. So, it is crucial to track
their stress levels early to avoid health problems and
complications. The purpose of this project was to build a
reliable and effective device to measure stress level easily.
I. INTRODUCTION
Stress is one ofthe major factors thatcontributes to physical
and physiological health problems. Stress may affect our main
body systems such as nervous system, musculoskeletal system,
respiratory system, cardiovascular system, endocrine system,
gastrointestinalsystemand reproductive system. If one of these
body systems shut down or not working properly due to stress,
human daily activities will be get influence too, Hence There is a
connection between stress and illness.
Unfortunately, stress disease is one of the most complex
diseasesin therapy, and most of the routes in the diagnosis and
knowledge ofthe levelof tensiontakes a lot of time, according to
public statistics, one person in every four people suffering from
anxiety in a period of his life, so the early detection of stress
protects persons acute complications.
II. BACKGROUND AND MOTIVATION
The treatment ofpsychiatric patients andpeople with stress
needs to sessions oftreatment and long to identify and diagnose
the disease,and most people with stress do notrealize the
seriousness ofits complications,leading to acute stress.
Add modern technologyhelps in detecting the levelofstress
that would help in the identification ofassociated with psychiatric
illnesses,and this will help the doctorto assess the psychological
state of the patient and therefore easier to reduce risks.
It will be invented a way to measure a reliable, easy to use,
reduce the financialand physicalburdenon the patientand alsoget
the results in a few minutes, as well as all that, will be to collect
and analyze the results in order to reach the range for stress
acceptable and range is unacceptable which is harmful to the
patient's health, so this project is a research project and applied.
The main objectives of this project can be summarizedas
follow:-
 Development a suite ofa wearable physiologicalsensors
for affective responses fromphysiologicalsignals,
namely, GSR, HR, and SKT.
 Design the sensors with ability to measure,store,and
transmit physiologicalparameters using low-power
wireless Bluetooth communication.
 Processingfinalresults ofthe physiologicalsignals to
find out range unacceptable stress by taking samples and
statisticalanalysis.
 Help patients to speedup the process ofdiagnosis and
thus speeding upthe treatment andreduces the riskof
complications ofsevere psychological.
III . Literature Review and Related Work
Stress is defined as a common physical reaction to events
that cause people to feel threatened and caused their emotional
state to become imbalanced [1]. An optimumstress level allows a
person to work at their optimumlevel of performance. However,
stress stops being positive and starts giving negative impact on
health,emotion and even daily activities. Figure 1.1 illustrates the
relationship of stress level and performance.

2. Figure 1.1:Stress curve [1].
Stress detection system (SDS) has been designed in previous
works for various applications such as measuring soldier stress,
computerusers stress, automobile drivers stress, and so on. So,
different methodologies and systems have been designed by
researchers to cope for the different purposes of research.
For example, Alberto de S.S. et al. proposed a noninvasive
SDS with heart rate (HR) and galvanic skin response (GSR) as
physiologicalsignals input [2].A database is needed for training,
validating and testingthe proposed systemand it is acquired by
performing a set ofpsychologicalexperiments with the purpose of
inducing stress in individuals. The researchers successfully
implemented the 7 proposed system with fuzzy logic and they
recorded 99.5% accuracy by acquiring HR and GSR data with 10-
second measurement and 90% if the period is reduced to 3 to 5
seconds.
Singh M. et al. proposed the use of four main parameters
and their derivatives, namely, Heart rate (HR), galvanic skin
response (GSR), electromyogram (EMG), and respiration rate
(RR) [3]. These four parameters are selected based on their
properties namely non-invasiveness when being acquired and
because their variation is strongly related to stress stimuli [4].
Sun F. T. et al. presented an activity-aware mental stress
detection scheme. The researchers obtained electrocardiogram
(ECG), galvanic skin response (GSR), and accelerometer data
from 20 participants [5]. The purpose of accelerometer in this
case is to measure the proper acceleration of participants across
three daily common activities: sitting, standing, and walking.
Mentalstressclassification for 10-fold cross validation obtained
92.4% accuracy with the aid of activity information derived from
the accelerometerclassification and80.9% accuracy for between-
subjects classification.
Shi Y. et al. used SDS to study both mental and physical
stress. For automatic stress detection, the researchers trained
personalized models using Support Vector Machines (SVMs).
Experiments on the recorded datashowthat the modelcan achieve
good precision and high detection rate. In this work,
Electrocardiogram (ECG), Galvanic Skin Resistance (GSR),
Respiration Rate (RR), Temperature are measured with different
sampling frequency [6].
IV. METHADOLOGY
In this project a portable noninvasive stress level detector
will be designed and implemented, this device will read the
physiological signals; namely, Galvanic Skin Response (GSR),
Heart Rate (HR), and Skin Temperature (SKT), that are low cost,
low power, and non-intrusive to be embedded on a wristband.
These wearable sensors will be capable oflong-termphysiological
monitoring, which is important when dealing with the treatment
and management ofmany chronic illnesses,neurologicaldisorders,
and mental health issues. Examples include: epileptic seizures,
autismspectrumdisorders,depression,drugaddiction and anxiety
disorders.
V . ANALYISIS
This section gives a detail description of the system
operation; The figure below illustrates the general block diagram
that is composed oftwo main parts; sensing part and processing
part.The sensingpart contains galvanic skin response(GSR)sensor
to measure the electrical conductance of the skin, which varies
with its moisture level, and heart rate sensor(HR)to determine the
numberof heart rate perminute, also,the skin temperature sensor
(SKT) that reading the skin temperature,this variable entered into
the accounts of the level of tension in the body.
Figure : Main Block Diagramfor the System.
The following parts describe the principle ofoperationof
each stage.
 Galvanic skinresponse (GSR)sensor Design
In this project a newnon-invasive methodto measure Skin

3. Conductance(SC)by Sensorthat providesinformation about
sweat gland activity onthe hand.
The Figure belowdemonstratesthe blockdiagramofthe
systemused to acquire the GSR data thoughelectricalsignals
from the GSR sensor.
Block diagramfor GSR circuit
 Wheatstone bridge
Figure below shows the circuit that use a Wheatstone The
purpose ofusing Wheatstone bridge observation is the change in
skin resistance and thus the conductivity of the skin, in order to
get different readings each case.
Wheatstone bridge circuit
In the pervious , R3 is used for calibration and GSR
electrodes representsthe resistance of the skin resistance. When
the voltage (v=5), then the voltage difference between two
terminals can be calculated by the below Equation .
Vd = V (
GSR
GSR + R1
−
R3
R2 + R3
)
 Voltage Follower
One of the problems expected to occur is non-arrival of electric
current to the rest of the circuit parts of required current. So to
avoid these problems,it has been used voltage follower or Buffer
which has a voltage gain of 1, with an ideal op amp gives simply:
Vout = Vin
Because the opamp has such high input impedance, it draw
very little current..
Voltage Followers circuit
 Differential Amplifier
The purpose of the differential amplifier is to amplify the
difference between two input terminals.
Differential Amplifier circuit
The differentialamplifier voltage is shownin the belowequation:
VO = (Vin+ − Vin) ×−
R7
R6
Only the difference will get amplified 24 times to be detect.



4.  Low Pass Filter
The low pass filter enable us to filter out unwanted signals it
allow low frequencysignals from0Hz to the cut-offfrequencyof
5Hz,.such that at high frequencies C1 and C2 act as short
circuits.
Low-Pass Filtercircuit
FC can be calculated by using R8, R9, C1 and C2 as expressed in
below equation :
FC =
1
2π√R8R9C1C2
Let C1= 22nF, so C2was calculated fromequation C2 = 150nF :
And R8, R9 is: R8 = 167.88 KΩ & R9= 1887.9 KΩ
 Heart Rate Sensor Design
The heart rate sensor, will be used to monitor the rate of heart-
beat of the patient. by choose Photoplethysmography technique.
This technique dependson thechangeofblood volume in the finger.
The block diagram shown in the below Figure is built to
illustrate the basic design of the proposed heart rate system.
Block diagramfor HR Sensor
 Infra-Red Transceiver
The Photoplethysmography technique,dependson the
amount of infra-red (IR) lights that reflected fromthe finger.
LED and phototransistorare arranged in the opposite direction
to sense thereflective IR-beamfrom the changes in arterial
blood volume in the finger,as shown in the belowfigure.
HR Sensor
Transmittance and reflectance are two basic types of
Photoplethysmography.The light is emitted into the tissue and
the reflected light is measured by the detector.
The following circuit showed in below figure, the
ON/OFF control scheme for the infra-red light source.
IR transceiver circuit
The transistor (2N3940) is chosen to deliver a constant
current for IR- LED. the forward current (IF) at which the LED
will transmit the desired wave length is at 20mA. This current is
delivered by the transistor as collector current IC=20mA . with
DC gain current (β) is equal 60the base current (IB) is:
Iβ =
Ic
β
=
20
60 ∗ 1000
= 0.33mA
The resistance R3 that generates the desired Iβis:
R3 =
Vcc−vBE
IB
, The base-emitter voltage (VBE) and VCC are
0.8V and 5Vrespectively ,hence the value of R3 equal 12.7KΩ

5.  Band Pass Filter and Non-inverting Amplifier
we need an amplifier and filter circuits to boost and clean the signal.In
Stage I instrumentationas shown in the Figure 4.10,the signalis first
passed through a passive (RC)high-passfilter(HPF) to blockthe DC
component .
Band Pass Filtercircuit
The cut-offfrequencyofthe HPFis 0.5Hz,then FC can be expressed
in equation : FC =
1
2π R4C3
Let C3 =4.7μF, then R4 =
1
2πfcC3
=68KΩ
The outputfromthe HPF goes to low-passfilter(LPF),with cut-off
frequency is 3.4Hz, then FC =
1
2πR6C4
Let C4 =100nF, then R6 =
1
2πfcC4
=470KΩ
The Op-amp operatesin non-invertingmode and hasgain 48,
gain can be calculated by equation 𝐺 = 1 +
𝑅6
𝑅5
the negative input ofthe Op-amp is tied to a reference voltage (Vref) of
2.0V that is generated using a zener diode, as the below figure
At the output is a potentiometer(P1)that acts as a manualgain control.
The secondstagealso consistssimilar HPF and LPF circuits as
shown in the belowFigure The two-steps use amplified and filtered
signalis nowfed to a third Op-amp, which is configured as a non-
inverting bufferwith unity gain.
 Comparator
The outputofthe comparatorgoes high.Thus,this arrangement
provides an outputdigitalpulse synchronous to heart beat, which
enable the microcontrollerto countheartbeat.
 SkinTemperature Design
will be used in this project to monitor skin temperature of
the patient.
so the sensor of this type NTC thermistor, and also non-linear,
and it must be converted to linear, and we note of the curve, if it
was taken a specified range, the change in this range will be
linearly, the following Figure illustrates range specified where be
the change of resistance with temperature linearly.

6. The following block diagrambuilt to illustrate the basic design of the
proposed system.
The skin temperature sensorvalue depending upon the temperature of
the body . so,The sensor resistance will varied as the temperature is
varied linearly, therefore, the sensor needs a calibration by
potentiometerR3 at a temperature equalto 18c, the output voltage (Vref)
equal 3.33 volt at by controlling the variable resistance (R3), thus the
result of (Vref -Vsensor) equal zero .
 Voltage Follower
the importance ofvoltage followerto ensure that the current will reach
for the circuit parts rest fully and properly without problem.
 Arduino
The result we have obtained fromdifference between Vref and Vsensor is
fixed equal0.05 volt between each temperature degreethat appear in the
curve shown in the following Figure .
Now, the relationship has become clear between temperature
and voltage difference, and thus build a linear equation of the
fourth degree, it has been the resulting equation after the
introduction of voltage values at each temperature ( C )as
follows:
𝐶 = 𝑎𝑉4
+ 𝑏𝑉3
+ 𝑐𝑉2
+ 𝑑𝑉+ 𝑓
C: Temperature , V: Voltage difference that taken fromthe
skin Where 𝑎 = 1.0245× 10−14
, 𝑏 = −2.16× 10−14
,
𝑐 = 1.911 × 10−14
, d = 20 , f = 18.
VI. RESULTS
52 samples distributedto 38sample for males and 14 for females.
Heart rate
output
on LCD
GSR output on LCD
SKT output
on LCD

7. 7
Based on these results,the resulting readingswere divided into levels
High, Mediumand Low
VII. CONCLUSION
As a conclusion, a prototype of stress detector has been
successfully developed. Based on the results obtained from the
project,it showed that the project achieved the proposed objective.
Heart rate, GSR and body temperature measurement can be monitored
through LCD display.
In conclusion, there are a few groups of people which are in
additionaldangerwhen they are in stressful conditions and a stress
detection system (SDS) can help to prolong their health sensor
handmade GSR sensor and Heart Rate Sensor is implemented with
the device is portable and userfriendly.The visualoutput peripherals
also make the overallsystemmore attractive and useful.By building a
stand-alone stress detector, people can use it to monitor their stress
level easily and understand what stressor cause the stress problem.
Also conclude when measuring psychologicaland heart rate of a
person leading to change his style if that condition is in danger and
thus protect himself from the risk might get him,and the main
advantages of this noninvasive system are fast and user-friendly
measurement.
VIII.ACKNOWLEDGMENT
We would like to thank Palestine Polytechnic University, College of
Engineering, and Electrical Engineering Department. Thanks from
our hearts for all support and for this worthy learning environment.
Also thanks to the head of hopefulness, our parents.
We would like to thankeverybody sharedin successofthis work
either by suggestion, directives, or tips. Thanks to Dr.
Ramziqawasmeh for theirgreat efforts in supervision,suggestion,and
providing experience to accomplishthis work.Also we want to thank
both Eng. Fida’aAlja’fra and Eng. ShehdaZahda For all helps and
worthy suggestions and tips to accomplish this project.
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