1. Developing an educational kit for I-V curve measurement of
photovoltaic devices
John Peter Raja David Raja, Loughborough University, Loughborough, Leics LE11 3TU
Abstract
This research main goal is to provide the kit to the students for understanding the basic concepts of solar
energy and their performance characteristics to explore sustainable energy solutions. Developed
educational kit provides the students with the tools needed to effectively investigate the performance of
PV. There are so many factors which affects the performance of Solar PV like temperature, Dusts, Shading,
Orientation and Tilt angle. So, periodic measurement of Solar PV performance is necessary. Electrical I-V
characteristics of a solar cell determines the device output performance and efficiency of the solar cell.
Since this kit is for teaching purpose a highly reliable method is needed to measure the I-V curve. So,
Electronic Load method using MOSFET is used to measure I-V curve of PV. Using this curve, the students
could understand the important terms such as short circuit current (Isc), open circuit voltage(Voc), Fill
Factor(FF) and its connection with the efficiency, students can also analyse the temperature and irradiance
effects on PV parameters for various conditions with both manual mode and automatic mode using
educational kit. Arduino is used as a microcontroller to control the variable load for measuring voltage,
current, temperature and irradiance. The resulting I-V curve for different temperature and irradiance
obtained from the final circuit shows very low noise disturbance and the curve is relatively smooth same
as keithley but with such a low cost of 40 pounds. From the analysis we see that use of this particular
method for the purpose of tracing I-V curve is very suitable and convenient.
Keywords – I-V curve, Arduino, MOSFET, Educational
Introduction
 Aim
To develop a device for educational purpose that can trace I-V curves based on the outputs from
photovoltaic modules.
 Objectives
1.To build a device that can trace current and voltage from the photo-voltaic devices using
Electronic Load(MOSFET)
2. To display the output as a graph in Excel
3. The Educational Kit should work in both Manual sweep mode and Automatic sweep mode.
4. To sense temperature and irradiance using sensors and display the data along with the I-V curve.
5.To test the educational kit in comparison to the currently used Keithley SMU with the post
graduate students.
Explanation of the Topic
The Current-Voltage characteristic curve demonstrates the relationship between the current flowing
through the electronic device and the applied voltage across its terminals. Graphing the obtained current
and voltage data is referred to as I-V curve and this curve usually acts as the tool to determine and
understand the basic parameters of a component or device. Similarly, in PV module the I-V curve
determines the conversion capability from solar energy to electrical energy for a particular irradiance and
temperature. The various parameters to characterise the solar cell are short circuit current (Isc), open
circuit voltage(Voc), Fill Factor(FF) which are obtained from the curve. The efficiency of the solar cell can
be analysed only from these parameters. So, it is an important measurement for understanding PV. [1]
Because of the benefits provided by Renewable Energy the study of renewables becomes important in both
school and college level. For a complete understanding of solar power, the I-V curve should definitely be
included in the solar education. Then only the students can analyse the temperature and irradiance effects
on PV for various conditions through practical work. Only practical work connects two different domains
(domain of real objects and observable things and domain of ideas). While, doing the experiments

2. practically it becomes interesting in the form of educational trip or real life projects and the difficult
concepts retains in our mind forever [2].
The theory of learning
There are several possible methods to obtain I-V curve of the PV which are enlisted below
Variable resistor and Bipolar Power supply method - In 2002, Malik, Salmi used variable resistor and
Bipolar power to obtain the I-V curve and examine the performance of PV. By varying the resistance, they
obtain current and voltage data but from their findings they figured out that short-circuit current cannot
be obtained using variable resistor. Then also by using BJT switch in Bipolar power they measured the
current and voltage data from PV to obtain I-V curve. [3].
Capacitive Load method - Marwan M. Mahmoud (2005) inspected the PV performance using capacitive
load and he claims that by using reasonable capacitor value to obtain I-V curve this method will be more
efficient comparing to first method. [4]
Electronic Load method - As an alternative method, Yingying Kuai, Yuvarajan (2005) examined the PV
module performance using MOSFET due to its fast variation of equivalent load resistance. He studied the
performance of this particular method both theoretically and practically by connecting the MOSFET with
PV to obtain different current and voltage data for graphing the curve. [5]
DC-DC Converter - Duran, Enrique, Bohorquez, Sidrach-de-Cardona, Carretero, Andujar (2005) found out
that SEPIC converter can sweep a complete I-V curve comparing to buck and boost converter from their
results. [6]. A best method can be applied to develop the educational kit only by comparing the advantages
and disadvantages of all methods. So, the compared advantages and disadvantages of every method is given
below:
Advantages and Disadvantages [7]
Method Advantage Disadvantage
Variable Resistor 1)Very cheap and easy to replace
2)Easiest method
1)Reliability and Response is
low
2)Need to program in case of
using programmable variable
resistor.
Capacitive Load
1)Excellent uses of their characteristic for
conducting a varying voltage
2) By charging the capacitor to negative
voltage second quadrant can be obtained.
1)Relatively unreliable in
circuits -For every new
measurement the capacitor
must be discharged
2)Difficult to control the
switches to operate in proper
sequence
Bi-polar Power 1)Simple circuit
2)Dark current can also be measured
using this method.
1)Switches(BJT) should be
operated in three modes
2)Cannot be applied for large
power systems
Electronic Load(MOSFET) 1)Highly reliable
2)Frequency of MOSFET is very high
(very fast)
1) It has high impedance and
low capacitance
2)High voltages may destroy the
MOSFET.
4 – Quadrant Power
Supply
1)Direct display of output is possible in
this method
2)With this method second and third
quadrant curves can also be obtained.
1)Cost is high
2)Difficult to build due to higher
number of switches. And cannot
be used for large PV systems
DC-DC Converter 1)High efficiency
2)Can handle a large output current
1)Complicated design with
ripples due to inductor
2)Cost factor

3. Methodology
This kit is for education purpose to teach in the classroom. So, it should be highly
reliable. Electronic load (MOSFET) method is the best method to use for obtaining the I-
V curve of PV. MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is used in
this method for switching the signals i.e. to control the flow of voltage and current in the
circuit. The MOSFET used is IRFZ44N it is an n-channel MOSFET the reasons to choose
an n-channel MOSFET for this circuit is it has high efficiency, low resistance and also it
is easy to scale. It has three terminals Source, Gate and Drain. Usually MOSFET works in
various modes here it operates in enhancement mode. The symbol 1 shows N-channel
MOSFET. For safety measures in case of higher voltage or current flows through
MOSFET there is an inbuilt diode in the MOSFET to protect it.
SYMBOL1
The PWM (Pulse Width Modulation) is given to the gate of MOSFET to control the voltage and current flow
in the circuit. It depends on the duty cycle, here the duty cycleis from zero percent to 100 percent to obtain
the complete I-V curve. The complete Project flowchart is given below:
Project Steps
Project Flow chart
Voltage Measurement – The Voltage from the PV is measured by connecting voltage divider circuit with
the PV input. For reducing the voltage magnitude from 22volts to 5volts two resistors of 4.621Kohm and
0.9958Kohm (four times difference) is connected in series across the input supply. The output from the
voltage divider is connected to the microcontroller to measure the voltage.
Current Measurement – The Current from the PV can be measured both directly and indirectly. Resistors
or Transistors can be used to measure directly, Hall effect coil and Rogowski coil can be used to measure
indirectly [8]. Here, Current sense resistor of 10ohm is used to measure the current from PV [8].
Irradiance Measurement – A Pyranometer is used to measure the irradiance. But the output from the
Pyranometer is low. So, an operational amplifier connected innon-inverting amplifier configuration is used
to amplify the voltage to 5volts. The resistors used in the configuration are 0.746ohm and 200Kohm
Temperature Measurement – A temperature sensor (LM 35) is used to read the temperature and the
microcontroller converts the analog data into digital data in Celsius.
Every measurement output is displayed in the serial monitor of Arduino and initially, it is copied to excel
for graphing the I-V curve but later it is made automatic using visual basics.

4. Circuit Diagram – To measure Voltage and current
Figure 1a – Circuit diagram to measure voltage and current
Components Specification/Model
Resistors R1 and R3 4.621Kohm
Resistors R2 and R4 0.9958ohm
Resistor R6 10ohm
Current Sense Resistor R5 10ohm
Capacitors C1 and C2 100microFarad
MOSFET n-Channel (IRFZ44N)
Power Supply 5volts
Microcontroller Arduino UNO
Photo-Voltaic At Standard Test Condition
Wp=5W, Vmp=17.5V, Imp=0.29A, Voc=22.0V,
Isc= 0.32A, Operating Temperature = -40degree to
+85degree. Max system voltage = 600v
Working Theory - The PV is connected to two voltage dividers with one resistor four time bigger than the
other one. The 22 volts from PV is converted to 5volts and given as analog input to the Arduino in pins A3
and A5. Current Sense resistor is connected in between the two voltage dividers. From the two voltage
values and current sense resistor value the current data can be obtained from ohm’s law (Ipv = (V1-
V2)/10ohm). The PWM for the GATE terminal of MOSFET is given from the Arduino PWM pin 5 to obtain
current and voltage data for duty cycle 0percent to 100percent. The ground of the circuit is connected to
the Arduino ground pin. The capacitors are connected with the circuit to smooth the curve.
Circuit Diagram - To measure Temperature and irradiance
Figure 1b – Circuit diagram to measure temperature and irradiance
Working Theory - The input from the irradiance sensor (Pyranometer) is connected to the non-inverting
amplifier configuration. Since, the pyranometer gives only 10microvolts/Wm-2 the amplifier is used to
amplify the voltage to 5volts [9] and given as analog input to the microcontroller (Arduino UNO). a power
supply of 5volt is used to power the amplifier. Finally, output from the temperature sensor is also given as
analog input to the Arduino.

5. Results – Steps of project progression
Voltage and Current Measurement
a) The Voltage Divider is connected directly across a voltage supply initially instead of PV, 4.621Kohm is
connected to the positiveside of the supply and 0.9958Kohm is connected to the negative side of the supply.
When the input of 19volts is given from the voltage supply an output of 3.72volts is obtained using voltage
divider and it is measured in the keithley. The main reason to convert the voltage is the Arduino UNO can
read only maximum voltage of 5volts.
Figure 2a – Voltage Divider Circuit Figure 2b – Keithley Output
b) To measure the current, a current sense resistor of 10ohms is also connected with the voltage divider.
As shown in the figure 2c, Keithley is used to read the current flow in the circuit.
Figure 2c – Current measurement Circuit
c) Since, PWM (pulse width modulation) using MOSFET acts as the load in the circuit. So, it is initially tested
with LED. The Digital pin 3 acts as the PWM pin to control brightness of the LED. The LED with 1Kohm
resistor is connected with drain terminal of MOSFET, the main reason to use a resistor with LED is to limit
the flow of current to prevent damage and source terminal is connected to the ground. Finally, PWM pin
from microcontroller is connected with gate terminal. When a duty cycle of 90percent is given to the
MOSFET the LED is seen bright as shown in the figure 2d. And an oscilloscope is also connected with the
MOSFET terminals to measure the duty cycle and voltage.
Figure 2d – MOSFET connection to control LED Figure 2e – Oscilloscope Output
R1= 1Kohm
R2 = 4.7Kohm
Current sense Resistor = 10ohms
Keithley
MOSFET
LED
1Kohm
Arduino UNO

6. d) The MOSFET is connected with voltage
divider and current sense resistor. But now an
additional voltage divider is also added along
with the present circuit to measure precise
values. The new circuit is simulated using
Falstad’s circuit simulator before being built in
the breadboard. The two voltage values from
the voltage dividers is connected to two Analog
pins (A3, A5) in the Arduino UNO and the
current from the circuit is calculated using
ohm’s law Ipv = (V1
– V2)/current sense resistor value. The PWM
pin 5 from Arduino UNO is connected to the gate
of MOSFET. Figure 2f – Circuit Simulation
The current and Voltage values for duty cycle 0 percent to 100 percent is obtained in the serial monitor of
Arduino UNO. The built simulated circuit is shown below in figure 2g. A voltage supply of 22volts is used
as input in the circuit to check the measurements. Arduino is programmed to measure an average of
1000values for both current and voltage.
Figure 2g – MOSFET connected with current and voltage measurement Circuit
e) Now a potentiometer is connected with circuit to measure the voltage and current values manually for
different duty cycles. The first terminal of Potentiometer is connected to 5volts, second terminal is
connected to the Arduino analog pin A1 and third terminal is connected to the ground.
Figure 2h – Manual Mode Circuit
The current and voltage of the circuit is measured using Oscilloscope and Keithley before drawing the
curve for ten different duty cycles the current and voltage values are obtained and I-V curve is drawn using
Excel. Which is shown below:
Voltage Supply
Mosfet
Voltage Dividers
Current Sense Resistor
Arduino UNO
Arduino UNO
MOSFET
Potentiometer
Current Sense Resistor
Voltage Dividers

7. Figure 2i – Oscilloscope and Keithley output for manual mode
The oscilloscope shows the voltage of 5.5 volts and keithley measures the current for voltages from 0 to
5.7volts. Then the serial monitor is used as display to read the output current and voltage values from the
circuit for ten different duty cycles. Instead of voltage supply as input, the PV is connected with circuit as
input
Figure 2j – PV connected with manual mode circuit Figure 2k – manual mode – I-V curve
f) Instead of manual mode, the current and voltage values are obtained automatically from the circuit and
Arduino is programmed to automatically calculate and display current and voltage values for duty cycle
from 0percent to 100percent. An average of 100000samples and 1000samples are taken separately and
the I-V curve is drawn for both program.
Figure 2l – I-V curve for 100000 samples Figure 2M- I-V curve for 1000 samples in automatic mode
PV
Manual Mode Circuit
Output in serial monitor

8. g) For 100000samples the I-V curve looks beneficial for understanding but for 1000 samples it is still not
beneficial. So, additional to the circuit a capacitor between voltage divider and current sense resistor is
added for limiting the ripples to get a smooth output. An oscilloscope is used to see the limited ripples. But
still there are ripples in the output voltage. So, as the final circuit a capacitor is added in the input end
across PV and another capacitor is added between voltage divider and MOSFET with a resistor between
source terminal of MOSFET and ground. And a 5volt power supply is connected along with PV as a
compensate for the voltage drop across the current sense and MOSFET stabilising resistors.
Figure 2N – Final circuit to measure I and V Figure 2O – I-V curve for the circuit
h) Temperature and Irradiance Measurement - To measure I-V curve for different temperature and
irradiance. The irradiance sensor is connected to the pin 3 of operational amplifier. The resistors
220Kohm and 1Kohm are connected with Pin 1and 2 of the amplifier. The output from the pin1 of amplifier
is connected to analog pin A4. Finally output from the temperature sensor is connected to the Analog pin
A0. A separate voltage supply is connected to pin 8 for powering amplifier.
Figure 2P – Circuit to measure temperature and irradiance
Figure 2Q – IV curve for different temperature
Capacitor C1
Capacitor C2
Resistor R6
5 volt supply
Voltage Supply – to power amplifier
Operational amplifier
Irradiance Sensor
Temperature Sensor
Voltage and Current Measurement Circuit

9. Discussion
The resulting I-V curve obtained from the final circuit shows very low noise disturbance and the
curve is relatively smooth. From the I-V curve of the final circuit, Short circuit current Isc of the PV is read
as 0.223amps and open circuit voltage of the PV is 16.5 volts. Since no MPP (Maximum Power Point)
Algorithm is used in the circuit precise values of Vmpp and Impp is difficult to read. But approximately the
fill factor and efficiency of the PV can be calculated. Using this curve, the students could understand the
important terms in the solar power to analyse the efficiency of the PV. There is a breakdown voltage in the
curve due to the additional 5volt supply to compensate loss. So, the students can also understand the
concept and causes of breakdown voltage.
From the I-V curves for different temperatures and irradiance. It is noted that as the temperature of the PV
decreases it has little effect on short circuit current but it has a high effect in open circuit voltage. It is
completely reverse for irradiance as the irradiance decreases it has little effect on open circuit voltage but
it has high effect on short circuit current. Using this curve, the students could understand the effects of
temperature and irradiance on PV.
Now the voltage, current,
temperature and irradiance
values are manually copied from
serial monitor of Arduino to Excel
for obtaining the I-V curve of PV.
But it is little bit difficult and
consumes some time so, using
visual basics the excel is
programmed to measure the
current, voltage, irradiance and
temperature values directly from
the Arduino UNO viaserial port 3.
When the button e is pressed a
particular set of values is
obtained. This developed excel
sheet can be send to the students
via e-mail or can be downloaded
from the online website.
Figure 3a – Excel Layout
As the final setup both circuits are designed in a strip board with a potentiometer for manual mode and a
push button for Automatic mode with a toggle switch between them to change the mode. And an enclosure
is used to cover the setup.
Figure 3b – Circuits in strip board Figure 3c – Educational Kit
Manual Mode
Automatic Mode
Toggle Switch
IV Tracer

10. Since there are no undergraduate students in the university in this period. The kit is tested with my
classmate. As a result, he can understand three different aspects such as the way to measure voltage,
current, temperature and irradiance, functions of important electronic components like microcontroller,
resistors, capacitors, MOSFET and operational amplifier. Finally, he can understand the terms of I-V curve
easily comparing to Keithley which he used in his first semester of Solar Power 1 lab.
The Educational Kit comes with PV and IV tracer.
The cost of PV is 15 pounds and the cost of IV
tracer is (Arduino UNO – 21.66 pounds, resistors
5pound, Mosfet – 1.24 pound, 25pence,
operational amplifier – one pound,)30 pounds.
So, all together the cost of educational kit is 45
pounds. Whereas the cost of keithley is 4,700
pounds. With such a low cost kit the students
will able to understand the terms and conditions
to measure the IV curve with same as keithley.
Figure 3d – Complete Setup
Conclusion
In conclusion, from the above analysis, we see that use of Electronic Load method to trace IV curve is very
reliable and convenient method to educate the students about Solar Power, apart from irradiance sensor
the circuit is also cost effective (35pounds) comparing to use of Keithley which is a high cost component.
The students can work intwo different modes by using this kit. In-case if they want to learn the duty cycles
connection with the curve they can use manual mode to graph the IV curve and in-case they want to learn
terms in the IV curve to obtain the efficiency then they can move directly to automatic mode. A little ripple
which was from the circuit is also eliminated by adding capacitors. The next improvement which can be
done to the kit was to add a LCD display directly to the kit for graphing the IV curve instead of using excel
in the laptop. Not only this kit can be used for undergraduate students it can also use by next year MSc
students for their understanding in solar power 1 lab with keithley. In the long term this kit circuits can be
modified with high power components to measure IV curve of large solar field.
Acknowledgement
I am very grateful to my supervisor Dr. Tom Betts, for patiently correcting my mistakes in the project. Who
cared and encouraged me in every steps on my stairway to knowledge heaven. I have found these
manifestations in him as a teacher, adviser, friend and a human being without whom it would never have
seen the light of day!
PV
I-V tracer Laptop

11. Appendices
References
[1] University, Loughborough. PhotoVoltaic Characterisation, Laboratory Notes for Solar 1 Module. 2015.
[2] R. Millar, "The role and purpose of practical work in the teaching and learning of science (first draft),"
2012.
[3] A. Q. Malik and Salmi Jan Bin Haji Damit, "Outdoor testing of single crystal siliconsolar cells," Renewable
Energy, vol. 28, no. 9, pp. 1433–1445, 2003.
[4] M. M. Mahmoud, "Transient analysis of a PV power generator charging a capacitor for measurement of
the characteristics,"Renewable Energy, vol. 31, no. 13, pp. 2198–2206, 2005.
[5] Y. Kuai and S. Yuvarajan, "An electronic load for testing photovoltaic panels," Journal of Power Sources,
vol. 154, no. 1, pp. 308–313, Mar. 2006.
[6] E. Duran, J. M. Enrique, M. A. Bohorquez, M. Sidrach-de-Cardona, J. E. Carretero, and J. M. Andujar, "A
new application of the coupled-inductors SEPIC converter to obtain I-V and P-V curves of photovoltaic
modules," p. 10, Sep. 2010.
[7] E. Duran, M. Piliougine, M. Sidrach-de-Cardona, J. Galan, and J. M. Andujar, "Different methods to obtain
the I–V curve of PV modules: A review," pp. 1–6, May 2016.
[8] [5] T. Gamblin, "Voltage divider circuits: Divider circuits and Kirchhoff’s laws - electronics textbook,".
[Online]. Available: http://www.allaboutcircuits.com/textbook/direct-current/chpt-6/voltage-divider-
circuits/. Accessed: Aug. 3, 2016
[9] B. Yarborough, "Components and methods for current measurement," 2012. [Online]. Available:
http://powerelectronics.com/power-electronics-systems/components-and-methods-current-
measurement. Accessed: Aug. 7, 2016.
[10] electronics +radio, "Non-Inverting operational amplifier circuit," 2016. [Online]. Available:
http://www.electronics-radio.com/articles/analogue_circuits/operational-amplifier-op-amp/non-
inverting-amplifier.php. Accessed: Aug. 25, 2016.
Arduino Program
int sensorPin1 = A5;
int sensorPin2 = A3;
int irradiancePin = A4;
int Temperaturepin = A0;
int fadePin = 5;
int ledPin = 13;
int PWM_duty;
float autoduty = 0;
long voltagesensorValue = 0;
long currentsensorValue = 0;
long irradiancesensorValue = 0;
long temperaturesensorValue = 0;
float Voltage;
float Current;
float Irradiance;
float Temperature;
float resistor1 = 1000;
float resistor2 = 4700;
float currentsenseresistor = 10;
float PWM_duty_display;

12. String SerialReadString;
char SerialReadChar;
void setup() {
TCCR0B = (TCCR0B & 0b11111000) | 0x02;
pinMode(ledPin, OUTPUT);
pinMode(fadePin, OUTPUT);
Serial.begin(9600);
}
void loop() {
// Serial.println("Voltage, Current, Irradiance, Temperature");
for(int x=0;x<=100;x++) {
autoduty=int(255*float(x)/100);
analogWrite(fadePin, autoduty);
SerialReadString = "";
while(SerialReadString != "e"){
if (Serial.available() > 0) {
SerialReadChar = Serial.read();
SerialReadString = SerialReadChar;
}
// delay(1000);
}
// Measure voltage, current, irradiance and temperature (average of 1000 samples each)
voltagesensorValue = 0;
currentsensorValue = 0;
irradiancesensorValue = 0;
temperaturesensorValue = 0;
for(int i=1;i<=1000;i++){
voltagesensorValue = voltagesensorValue + analogRead(sensorPin2);
currentsensorValue = currentsensorValue + analogRead(sensorPin1);
irradiancesensorValue = irradiancesensorValue + analogRead(irradiancePin);
temperaturesensorValue = temperaturesensorValue + analogRead(Temperaturepin);
}
voltagesensorValue = voltagesensorValue/1000;
Voltage = ((5./1023.)*voltagesensorValue)/(resistor1/(resistor1+resistor2));
currentsensorValue = currentsensorValue/1000;
Current = ((5./1023.)*currentsensorValue)/(resistor1/(resistor1+resistor2));
Current = (Voltage-Current)/currentsenseresistor;
irradiancesensorValue = irradiancesensorValue/1000;
Irradiance = ((5./1023.)*irradiancesensorValue*450);
temperaturesensorValue = temperaturesensorValue/1000;
Temperature = (temperaturesensorValue/1024.0) * 5000 / 10;
Serial.print(Voltage,3);
Serial.print(", ");
Serial.print(Current,3);
Serial.print(", ");
Serial.print(Irradiance,1);
Serial.print(", ");

13. Serial.println(Temperature,1);
}
Serial.println();
}