1. MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF
ELECTRICALAND ELECTRONICS ENGINEERING
EE 300
SUMMER PRACTICE REPORT
CEM RECAİ ÇIRAK
1674936

2. Student Name: Cem Recai ÇIRAK
Student ID: 1674936
Student E-mail Address: e167493@metu.edu.tr
Student Contact Number: +90 505 2852872
Summer Practice EE 300 or EE 400?: EE 300
SP Beginning and Ending Date: 30/6/2014 – 25/7/2014
SP Specialization Area: Electromagnetics, Electronics
Name of the SP Company: OKIDA Elektronik San. ve Tic. Ltd. Şti.
Location of the SP Company: Sanayi Mahallesi, 1656. Sokak, No: 23,
Esenyurt – Istanbul | TURKEY
Contact Number of the SP Company: +90 212 6729933
E-mail Address of the SP Company: info@okida.com
Name of the Engineer: Barış ÇARKACI
Contact Number of the Engineer: +90 538 6196679
2

3. TABLE OF CONTENT
1. INTRODUCTION.....................................................................................................4
2. DESCRIPTON OF THE COMPANY........................................................................5
2.1. Name of the Company..................................................................................5
2.2. Location of the Company.............................................................................5
2.3. General Description of the Company...........................................................6
2.4. Description of the R&D Department...........................................................8
2.5. Brief History of the Company......................................................................8
3. FAMILIARISING WITH ELECTRICAL COMPONENTS.....................................9
3.1. Bridge Diode................................................................................................9
3.2. Relay...........................................................................................................10
3.3. Toroidal Inductor........................................................................................12
4. SOLDERING TECHNIQUES................................................................................13
4.1. Through-Hole Soldering.............................................................................14
4.2. Surface Mount Soldering...........................................................................15
5. PROTOTYPE TESTING.........................................................................................16
5.1. EMC (Electromagnetic Compatibility)............................................16
5.1.1. Conducted Emissions..........................................................17
5.1.2. EFT (Electrical Fast Transient)...........................................18
5.2. Thermal Analysis.............................................................................21
6. CONCLUSION.......................................................................................................21
7. REFERENCES........................................................................................................22
3

4. 1. INTRODUCTION
I have performed my second year summer practice (EE 300) in OKIDA Electronics. OKIDA
Electronics develops and produces electronic modules for the white good industry and security
systems. My summer practice had lasted for 4 weeks (20 workdays) between 30 June 2014 and 25
July 2014. I carried out my practice in R&D (Research and Development) department of OKIDA
Electronics.
In R&D department, engineers and technicians work for designing, developing and testing
different electronic modules upon the demands of clients. At first step of designing a new product, a
sample product is designed and produced to send to the client company. Then regarding the
feedback coming from the client, sample product is modified and developed. At final step, the
modified product tested for electromagnetic compatibility and thermal analysis. If product fails at
one of these test, it modified again and again until passing all tests. Then, product is finalized and
get ready to mass production.
I started my summer practice work with familiarising with some electrical components.
Then, I had worked at production of electronic cards for prototypes. I advanced at soldering
techniques. I also tested products for electromagnetic compatibility and thermal analysis.
In this report, works and observations that I had done during my summer practice are
included. At beginning, there is a description of the company which is involving necessary details
about it. Details of my summer practice work are placed after the description of the company part.
At the end of report, there are conclusion and reference parts.
4

5. 2. DESCRIPTION OF THE COMPANY
2.1. Name of the Company
OKIDA Elektronik Sanayi ve Ticaret Limited Şirketi.
2.2. Location of The Company
OKIDA Electronics has one factory which is located in Esenyurt, Istanbul, Türkiye. So the
company is located in industrial zone. There are also two distribution agencies which are Italian
Agency located in Italy and European Agency located in Germany.
OKIDA Elektronik San. ve Tic. Ltd. Şti.:
Phone: +90 212 6729933
Fax: +90 212 6729939
E-mail: info@okida.com
Address: Sanayi Mahallesi, 1656. Sokak, No: 23,
Esenyurt – İstanbul | TURKEY
Italian Agency:
Giovanni Giannini Mochi
Phone: +39 335 8126567
E-mail: giovanni.gianninimochi@fastwebnet.it
European Agency:
Freddy Frindt
Phone: +49 262 5958929
E-mail: freddy@frindt.de
5

6. 2.3. General Description of the Company
OKIDA Electronics develops and produces electronic modules for the white and brown
good industry and security systems since 1987. Main products of OKIDA Electronics are oven
timers; control modules for oven, cooker hood and hob; auto, home and office security systems.
OKIDA Electronic employs 75 people working in a factory which has 4000 squaremeter
closed area. 15 out of 75 employees are engineers and technicians. All of the products are designed
in R&D department. Production is fully automized with latest technology machinery and the whole
process – starting from the incoming raw material up to delivery – is strictly supervised.
As a result of this elaboration, OKIDA Electronics is exporting to over 20 countries from
Europe, South America and Asia. Some of these countries are Bulgaria, Colombia, Croatia, Czech
Republic, Germany, Iran, Italy, Poland, Portugal, Slovenia, Spain and United Kingdom.
Mission & Vision:
OKIDA Electronics has the principle of always keeping customer satisfaction and product
quality at first priority, following new technologies and updating the company accordingly.
Quality notion of OKIDA Electronics starts at the designing stage followed by well
controllable, traceable, fault free, practical and efficient production process.
Based on ISO-9001, OKIDA Electronics employees are periodically trained to improve their
skills and knowledge, taking into account quality reports and technological evolutions, resulting in a
continuously improving quality management system.
6

7. Organizational Structure:
7
Figure 1: Organizational Structure of the OKIDA Electronics

8. 2.4. Description of the R&D Department
4 engineers and 3 technicians are working in R&D department. R&D department is
responsible for designing, development and testing processes of electronic modules in accordance
with requests of customer companies. Deveplopment process of an electronic module starts with
PCB (Printed Circuit Board) design and mechanical design step. PCB design is supperted by
Mentor Graphics PADS PCB Design and SolidWorks is used for mechanical desing. Then through-
hole and surface mount typesetting process is performed. Next step is programming the
microcontroller which is used in electronic module. Microchip PICs and ARM based
microcontrollers are commonly used. Therefore programming languages like Assembler, C, C++
and C# are used in software development.
After first prototype is completed, it is developed passing through design verification
phases. Standby consumption, EMC performance and thermal performance are measured and
reported. Life tests of the developed products are also carried out and reported. At final step,
verified prototype becomes ready to mass production and is sent to production department.
2.5. Brief History of the Company
In 1987, OKIDA Electronics is founded and starts to operate under 4000 squaremeter closed
area in Büyükçekmece, Istanbul. The company, designing and producing electronic circuits, fast
growths in white and brown good industry and security systems. Financial turnover of the company
reached 1000000 € in 2006, and 2500000 € in 2007. The company get %60 of its income from
exports. Also, number of employees rose up to 50.
In 2008, OKIDA Electronics became the first company which using RGB-LCD Display
Technology in kitchen utensils. In cooperation with far eastern and european producers, another
project which applying touchscreen technology to kitchen utensils was conducted by the company.
In 2013, OKIDA Electronics reached 10000000 € revenue, %40 export rate and 75
employee.
8

9. 3. FAMILIARISING WITH ELECTRICAL COMPONENTS
My summer practice started with familiarising some electrical components which are
frequently used in production of electronic modules. I also learnt the usage of some components
that I did not used in electrical and electronic circuits labrotary courses before such as relays and
toroidal inductors.
3.1. Bridge Diode
Bridge diode is component which is basically an arragement of four diodes in a bridge
circuit configuration that provides the same polarity of output for either polarity of input.[1]
When
used in its most common application, for conversion of an alternating current (AC) input into a
direct current (DC) output, it is known as a bridge rectifier.
The DC output from a bridge rectifier is not smooth and it varies a lot with time. Therefore
for smoothing the output of rectifier, a capacitor with a high capacitance is added. So that rectifier
varies less. This is mostly important for electronic modules and devices.
9
Figure 2: Bridge Diode

10. As the voltage in the rectifier circuit increases, the capacitor stores charge. When the voltage
begins to fall, the capacitor begins to discharge, keeping the DC more constant. When the voltage
rises again, the capacitor begins to store charge again. This process repeats and keeps the DC supply
smoother.
3.2. Relay
Relay is an electromechanical component used as electrically opeated switch. Relays mostly
use an electromagnet to control a mechanical switch.[2]
10
Figure 3: Bridge Diode Diagram
Figure 4: Full Wave Rectified and Smoothered DC Output Waveforms

11. A simple electromagnetic relay consists of a coil of wire wrapped around a soft iron core, an
iron yoke which provides a low magnetic resistance (reluctance) path for magnetic flux, a movable
iron rotor (armature) and one or more sets of contacts. The armature is hinged to the yoke and
mechanically linked to one or more sets of moving contacts. It is held in place by a spring so that
when the relay is deenergized one of the contacts in the relay is closed and the rest is open. Number
of the contacts may change depending on function of relays.
11
Figure 5: Relay
Figure 6: General Relay Diagram

12. When an electric current is passed through the coil it generates a magnetic field which
activates the armature. If a contact was closed when the relay was deenergized, the movement of
armature opens the contact and breaks the connection, and vice versa if the contact was open. When
the current to the coil is switched off, the armature is returned by a force which is usually provided
by a spring, approximately half as strong as the magnetic force, to its relaxed position.
3.3. Toroidal Inductor
Toroidal inductor is an electronic component consisting of a circular ring-shaped magnetic
core of high magnetic permeability material around which wire is coiled to make an inductor. An
inductor with a closed-loop core can have a higher magnetic field and higher inductance.[3]
The advantage of the toroidal inductor is that due to its symmetry the amount of magnetic
flux that escapes outside the core (leakage flux) is minimum. Therefore it radiates less
electromagnetic interference (EMI) to nearby circuits or equipment. Since low EMI has increasing
importance in modern low power high frequency electronics, toroidal inductors are more commonly
used.
12
Figure 7: Toroidal Inductor

13. Absence of circumferential current and the axially symmetric layout of the conductors and
magnetic materials are sufficient conditions for total internal confinement of the magnetic flux
intensity. Because of the symmetry, the lines of magnetic flux must form circles of constant
intensity centered on the axis of symmetry. The only lines of magnetic flux are inside the toroidal
winding. Therefore, Ampere's Law states that the magnetic flux intensity must be zero outside the
winding.
4. SOLDERING TECHNIQUES
In second part of my practice, I hardly worked on soldering techniques. I practice both
through-hole soldering and surface mount soldering.
13
Figure 8: Magnetic Flux Intensity and Current Diagram
Figure 9: Through-Hole and Surface Mount Components

14. The soldering process is the means by which electronic components are mechanically and
electrically connected into the circuit assembly. It is the only permanent way to fix components to a
circuit board.[4]
However, it is easy to waste many hours preparation and design work by poor
soldering. Adhering to good soldering practices will preserve the inherent reliability of the original
components and ensure a good, reliable connection of the component into the circuit assembly. To
have a good chance of success, a guideline which involves soldering techniques should be followed.
There are four process stages in soldering:
1. Preheat: The preheat process is very important in any kind of soldering process. To avoid
thermally shocking the components, PCB assemblies must be preheated. Immediate or latent
damage can occur to the components if they are not preheated properly.
2. Soak: A soak period is useful so that components of differing thermal mass will approach
a similar temperature prior to the peak stage. During reflow soldering, this is the period
where the flux begins to break down the oxides which would inhibit solder adhesion.
3. Temperature: The range of the peak soldering temperature depends on several factors, two
of plating and body compositions. The minimum soldering temperature range should be at
least 5-10°C higher than the eutectic melting temperature of the plating alloy. The maximum
soldering temperature should be at least 5-10°C lower than the melting temperature of any
thermoplastic components.
4. Time: The devices must be held at the peak soldering temperature long enough to make
sure the proper wetting of the solder connections. However, keeping the peak soldering time
to a minimum to avoid the possibility of damage to the devices is important.
4.1. Through-Hole Soldering
Using a soldering iron in good condition is important. If it looks in bad condition it will not
solder a good joint. The shape of the tip may vary from one soldering iron to the next but generally
they should look clean and not burnt.
14

15. A PCB eraser is used to remove any film from the tracks. This must be done carefully
because the film will prevent good soldering of the components to the PCB. The tracks can be
checked using a magnifying glass. If there are gaps in the tracks, sometimes they can be repaired
using wire but usually a new PCB has to be etched. Placing the PCB, with its components in
position, in the bull clip will steady the PCB when trying to use the soldering iron.
The heated soldering iron should then be placed in contact with the track and the component
and allowed to heat them up. Once they are heated the solder can be applied. The solder should flow
through and around the component and the track. Having completed soldering the circuit the
extended legs on the components need to be trimmed using side cutter pliers.
4.2. Suface Mount Soldering
Two terminal devices such as resistors and caps are generally the easiest parts to start out
with. After placing the part onto its location on the PCB, the joint between the terminals on the part
and the PCB are heated while touching it with solder, then solder will flow. After one side has been
soldered, the opposite side is soldered in the same way quickly. Surface tension of the liquid solder
should center the part. Solder tip and the solder strand should be used to push the part into place. If
too much solder is got on the part, solder wick will be useful to suck up any extra.
Soldering small outline integrated circuit (SOIC) parts are not much different from two
terminal devices. After lining up the part, single lead pin is tacked, and the part is pushed. So, the
pins become aligned with the pads. Then each of the other pins are soldered. If solder bridges across
any of the pins, it is not so important. The solder can be wiped away with solder wick easily.
Even if most people are intimidated by the quad flat pack (QFP) parts that have a hundred or
more pins, these are just as easy to solder. People mistakenly think that they need to solder each pin
individually without causing any solder shorts. In reality, the approach is to tack the part into
position, and then to cover it with solder ignoring any shorts. Since, these can easily be removed
with solder wick.
15

16. The hardest part is to get the chip aligned properly on the pads. If things are aligned can be
determined because there will be a moire effect if they are not. Magnifying glasses of 3X can be
very useful in seeing whether things are lined up or not. Once the chip is lined up, a single pin is
tacked down to its pad. Then to make sure things are aligned it is rechecked. Then a second point
which fixes the chip such that it can not move or rotate is tacked down. At this stage, wipe solder
flux across all the pins, so that solder will freely flow. Then freely melt solder acrosses all the pins.
It is okay to short them out with a big flowing solder glob. The solder glob is gently wiped toward
one side of the pins, so that it collects on one corner. Then solder wick is used to remove the excess
solder. The solder wick is put on top of the glob and the soldering iron is pressed down upon the
braid. The solder will be sucked into the braid. The solder wick should be wiped in a direction with
the pins, and not lateral to the pins, as this will bend them or cause pads to be lifted. This process is
repeated on all four sides, and then it is sprayed with solder flux remover. Then it is checked for
shorts. If any short is found, they should be wiped away with heated solder braid. By this way,
putting on a 200 pin thin quad flat pack (TQFP) part will take only a few minutes.
5. PROTOTYPE TESTING
The last part of the practice was about prototype testing. All electronic module prototypes
were subjected to some electromagnetic compability tests and thermal analysis. Electromagnetic
compability tests are conducted by using specialized devices. For thermal analysis, both testing
oven and thermal camera are used.
5.1. EMC (Electromagnetic Compatibility)
Electromagnetic compatibility (EMC) is the branch of electrical sciences which studies the
unintentional generation, propagation and reception of electromagnetic energy with reference to the
unwanted effects (Electromagnetic interference or EMI) that such energy may induce. The goal of
EMC is the correct operation, in the same electromagnetic environment, of different equipment
which use electromagnetic phenomena, and the avoidance of any interference effects.
16

17. 5.1.1. Conducted Emissions
The term conducted emissions refers to the mechanism that enables electromagnetic energy
to be created in an electronic device and coupled to its AC power cord. The allowable conducted
emissions from electronic devices are controlled by regulatory agencies. If a product fails a
conducted emissions test, the product can not be legally sold. The primary reason that conducted
emissions are regulated is that electromagnetic energy that is coupled to a power cord of product
can find its way to the entire power distribution network that the product is connected to and use the
larger network to radiate more efficiently than the product could by itself. Other electronic devices
can then receive the electromagnetic interference through a radiated path (or much less frequently, a
direct electrical connection). The frequency range where conducted emissions are regulated is
typically lower than the frequency range where radiated emissions are regulated. The longer
wavelengths where conducted emissions are a problem need a much larger antenna to radiate and
receive electromagnetic interference than the shorter wavelengths.
Conducted immunity problems are primarily due to large variations or transients on the
power distribution network where the product receives its power. Lightning, electromagnetic pulses
(EMP) and power surges are examples of types of electromagnetic interference that can couple to a
product directly through its AC power cord. A well designed power supply and power supply filter
will help a product increase its resilience to some of these phenomena.
A Line Impedance Stabilization Network (LISN) performs conducted emissions
measurements. A LISN provide two functions, to isolate the test system within its boundaries and
to provide a measurement point. The operator selects the frequency range, which is usually
governed by the standard being used.
A LISN couples the interference from the Equipment Under Test (EUT) connection to the
measuring equipment and at the same time presents a stable and well-defined impedance to the
EUT across the desired frequency range. The actual measured voltage depends on the ratio of
source impedance of the EUT and load impedance of the LISN. So, if the impedance were not
stabilized, there would be no repeatability between different test locations.
17

18. Like all EMC transducers, LISNs must be calibrated and their calibration factors (sometimes
called transducer factors) taken into account whenever they are used in an accurate measurement of
conducted emissions. Earth of the LISN is connected to the ground reference plane (GRP) of the
test setup. Since this is the ground reference for the measurement, no extra radio frequency (RF)
impedance should be introduced by this connection. Because it would affect both the impedance
seen by the EUT and the voltage developed across impedance the LISN. This means that wires or
straps of more than a few centimeters must not be used, since their inductance is unacceptable. The
best connection here is a solid metal bracket, firmly bonding the LISN to the GRP.[5]
5.1.2. EFT (Electrical Fast Transient)
Electrical Fast Transients (EFT) are caused anytime a gaseous discharge occurs (a spark in
air or other gas), the most common being the opening of a switch through which current is flowing.
As the switch is opened, arcing occurs between the contacts, first at a low voltage and high
frequency while contacts are close together, and later at a higher voltage and lower frequency as the
contacts become separated. Coupling of the EFT into electronic products occurs when power cables
handling high currents are run in close proximity to power, data, and I/O cables.
Electronic products are tested for EFT immunity to insure their continued reliable operation
if subjected to realistic levels of fast transients. The European Union’s EMC Directive mandates
EFT testing for virtually all electrical and electronic products as a condition for obtaining the CE
Mark before shipping to a member state of the European Union.
The EFT test aims to simulate the disturbances created by a showering arc at the contacts of
ordinary AC mains switches or relay contacts as they open, due to the flyback voltages caused by
inductive energy storage in the current path. The standard waveform for the EN 61000-4-4 EFT test
consists of a single unidirectional impulse repeated at 5 kHz rate in bursts lasting 15 milliseconds
each and at 100 kHz rate in bursts lasting 0.75 milliseconds each, with three bursts per second.[6][7]
18

19. It is worth noting that even though it is a power signal that is transmitted on the Power-over-
Ethernet cable, this transmission is still on a communication data cable, which means that it is
considered as such when installed and used. Consequently, it belongs to the I/O signal, data, and
control ports category.
Signal and data cables have the transient bursts injected via a specified capacitive clamp.
These clamps are easily made using common materials by following the detailed construction
drawing in Figure y. The clamp can also be replaced with wound tape or conductive foil 1 meter
long that creates the equivalent capacitance to the standard clamp (100pF).
19
Figure 10: EFT Waveform with 50 Ω Load
Figure 11: General Graph of EFT Impulses and Bursts

20. Where the 1 metre length of the clamp or equivalent is too long, alternatives can be used as
long as they give the equivalent capacitance, even to the extent of connecting the output of the
generator directly to the cable screen or signal terminals via discrete 100pF capacitors (high-voltage
ceramic type). Because of the lack of distributed coupling, these alternatives (especially the discrete
capacitors) are likely to give different results from the standard clamp method so should be used
with caution, and only where the 1 meter clamp can not be used.
When testing signal and data cables be aware that the capacitive clamp has no directionality,
so any auxiliary equipment being used in the test setup is also subject to the EFT on its cables.
Suppression techniques may be needed for the auxiliary equipment (such as passing the cables
through a bulkhead-mounted filter in a screened-room wall or clip-on ferrite cable suppressers) to
allow the response of EUT to be measured correctly. Suppressers based on chokes and ferrites are
preferred, as capacitive filters may prevent the signal cable from experiencing the coupled EFT as it
will in a real application.
20
Figure 12: EFT Test Setup

21. 5.2. Thermal Analysis
Power dissipation is an important issue in present-day PCB design. Power dissipation will
result in temperature difference and pose a thermal problem to a chip. In addition to the issue of
reliability, excess heat will also negatively affect electrical performance and safety. The working
temperature of an integrated circuit should therefore be kept below the maximum allowable limit of
the worst case. In general, the temperatures of junction and ambient are 125 °C and 55 °C,
respectively. The ever-shrinking chip size causes the heat to concentrate within a small area and
leads to high power density. Furthermore, denser transistors gathering in a monolithic chip and
higher operating frequency cause a worsening of the power dissipation. Removing the heat
effectively becomes the critical issue to be resolved.
6. CONCLUSION
My summer practice became my first professional working experience. Therefore, these
practice provides me lots of materials which may support to improve my vision about not only
engineering but also operation principles, business life, management pyramid etc.
On the other hand, I also improved both my engineering and technical skills. In first half of
my summer practice, I worked like a technician. I learnt about working principles of some electrical
components which I did not use in laboratory courses at school before and I used them. I also
practiced a lot practice about soldering techniques and debugging techniques. In second half of my
summer practice, I worked like a test engineer. I used different hi-tech test equipments and
implemented different testing procedures.
In brief, this practice made a good contribution to my knowledge about different areas.
Hence, I believe that my summer practice was really efficient for me.
21

22. 7. REFERENCES
1. http://en.wikipedia.org/wiki/Diode_bridge
2. http://en.wikipedia.org/wiki/Relay
3. http://en.wikipedia.org/wiki/Toroidal_inductors_and_transformers
4. “Recommended Soldering techniques” Diodes Inc., 2014, Rev. 02. Available
on-line http://diodes.com
5. “EMC Testing Part 1 – Radiated Emissions” Keith Armstrong and Tim
Williams, EMC + Compliance Journal February 2001, pages 27-39. Available
on-line at www.emc-journal.co.uk.
6. “EMC Testing Part 2 – Conducted Emissions” Keith Armstrong and Tim
Williams, EMC + Compliance Journal April 2001, pages 22-32. Available online
at www.emc-journal.co.uk.
7. “EMC for systems and installations” Tim Williams and Keith Armstrong,
Newnes, January 2000, ISBN 0-7506-4167-3.
22