laborator 8 celule fotovoltaice si aplicatii

8/3/2019 Laborator 8 Celule Fotovoltaice Si Aplicatii

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r--------------------~

10 in 1DELUXESOLAR ENERGY

EXPLORATION LABProduct Stock# C6853

. . . . . _ . . . . . . . . C HANEY~ELECTRONICS, INC.


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Copyright 2000 Chaney Electronics, Inc. No part of this manual may be reproducedin any way without prior permission from Chaney Electronics, Inc. You are free to photocopy theParts Inventory (pgs. 5-6) and the Replacement Parts Order Forms at the end of this manual.

LECTRONICS, INC.


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10 in 1Deluxe Solar Energy Exploration Lab H-+-+-Page

Introduction " 4Parts Inventory 5Tips on Using the Breadboard 7Instructional Experiments1. Introduction to Solar Cells 82. Solar Panels 103. Diode Action 124. Solar Powered DC Motor 145. Resistors and Color Code 176. Solar Power Alarm 207. Solar Power Storage 228. Solar Powered Flashing Light 249. Solar Pulsating Alarm 2610. Another Environmentally Safe

Method of Generating Power 29Useful FormulasOhm's Law Circle 32Resistance Formulas 33Optional Experiments 34Replacement Parts Order Forms 35


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Introduction to the 10 in 1Deluxe Solar Energy Exploration Lab

Power from the sun can be harnessed in many different ways. This clean,environmentally safe form of energy is readily available and it is being used toheat water, heat buildings, cook food, provide electricity and as well as manyother applications.The focus of this exploration lab will be on the exciting application of using

the sun's free energy to produce electricity and using this electricity to powerelectrical and electronic devices. With the various environmental problems withfossil fuels and rising prices of oil, the world's population will need to developsystems to use more of the free energy provided by the sun. The sun shinesapproximately 1000 watts of energy per square meter of the planet's surface ona bright sunny day. The challenge is collecting this energy in a cost effectivemanner. As we will discover, solar panels are able to tap into this free source ofenergy and provide us with useful electricity from the sun. As the cost of thesepanels continue to go down, their usage will continue to increase.

The 10 in 1 Deluxe Solar Energy Exploration Lab will allow you to study asilicon solar cell and give you a basic understanding of how solar cells andpanels work. These concepts will be reinforced through performing an array offascinating, hands on experiments.

All components in this Lab are reusable, and we use a universal pluq-inbreadboard so that no soldering is required. In addition, all of the componentsin this Lab are replaceable for a minimum cost i f they become damaged ormisplaced.Before you begin using the Lab, we recommend that you take an inventory

of all of the parts. Pages 5 and 6 are a Parts Inventory with all of the compo-nents used in this Lab. Enjoy your learning experience!


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Before you begin to use your 10 in 1 Deluxe SolarEnergy Exploration Lab, please check off the parts below

to verify that you have everything that you need.Note: these inventory pages may be photocopied.Item SchematicSymbol

10Motor with Holder10 noneRed Plastic Propeller

10 [ ; 1 - 7Flashing Red LED

10 - - - 1 E - = -uper Capacitor

Odd Shaped Silicon Solar Cell in Plastic Case

---+--1- @ I - - - + - - +

- - - - - + - l @ 1 - + - -- SP +

Electronic Sounder


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Schematic Symbol=======CITOJ=======12Q Resistor (Brown Red Black)

1KQ Resistor (Brown Black Red)

15KQ Resistor (Brown Green Orange)

1N4001 Diode

Breadboard

Pushbutton Switch

Short Wires


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The universal breadboard is used to create tem-porary circuits for learning and testing purposes. Thebreadboard has many columns of holes or socketsthat you insert the leads of components or wiresneeded to build a circuit. If we could see inside thebreadboard we would see that the columns of fivesockets are connected. This means that each col-umn of five sockets is the same point on a sche-matic diagram (See Figure 1).

No InternalConnection

Figure 1 - Cutaway view of a When inserting components into the universal universal breadboardbreadboard, be sure to grasp the component near !..- ....Jthe end of the lead. If you hold the component itself when inserting it, you will probablybend and may even break the lead making it useless (See Figure 2). When installing the resistors, make sure that the correct value resistor is used. There isno polarity for resistors. When installing electrolytic capacitors the polarity (+) must be observed. If an electrolyticcapacitor is marked with only a (-) symbol then the opposite lead is +. Make sure that you install LEOs with its short lead (cathode lead) in direction shown. Diodes are installed with a polarity indicated by a band (cathode). Finally, always observe the color code polarity shown for the solar panel.

\

N. c o ' _ ._n

RIGHT WRONGFigure 2 - How to insert a component

into the universal breadboard.

IN


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INTRODUCTION TO SOLAR CELLSThe solar cell, also referred to as a photo-voltaic cell, was so named because of thefact that the word photo ight and voltaic :::::electricity. Solar cells can be connected to-gether electrically to form solar panels. So-lar cells and solar panels are found in solarpowered lights inyards, solar powered oceanbuoys, satellites, calculators, solar radios,solar powered home electricity generators,etc.Let's study the individual solar cell or photo-voltaic cell. A French physicist namedElmond Becquerel first described the pho-tovoltaic effect in 1839. He had discoveredthat certain materials would produce smallamounts of electrical currents when exposedto light. The first practical application ofBecquerel's discovery was the introductionof selenium cells. These selenium cells wereused in electric eyes to open doors and in

light measuring meters for photography. Theconversion of sunlight into electricity was soinefficient in selenium cells that it could notbe used as a practical source of electricalpower. Inthe 1940's a breakthrough that wasto spur photovoltaic technology developmentoccurred. It was the development of theCzochralski process. This process allowedthe manufacture of highly pure crystallinesilicon. Basically it was a special furnacewhich allowed a cylindrical crystal of semi-conductor material (such as silicon, germa-nium or gallium-arsenide) to be produced.This solid cylindrical crystal was then slicedinto thin semiconductor wafers. In 1954 sci-entists at Bell Laboratories used theCzochralski process to produce the first sili-con solar cells. The early applications ofthese silicon solar cells were to produceelectricity for satellites.

HOW DOES A SILICON SOLAR CELL WORK?used to create a variety of solar cells. Al-most all cells are coated with an anti-re-flective coating to enable them to captureas many photons as possible instead of re~flecting them away. A more detailed de-scription of how solar cells work can befound in physics text books or on theinternet.

A silicon solar cell is made of a "sandwich"of two types of silicon semiconductor ma-terial, a P-type and an N-type. As photonsfrom the sun strike the top surface of thesolar cell the photons from the sun causeelectrons in the N-type material to flow fromthe N-type semiconductor material throughthe collection bar on the top surface of thecell, then through a load circuit by .--------------------_t::;tr1way of a wire back to the bottom sur-face of the cell where the electronscombine with "holes" in the P-typematerial. The process of generat-ing electricity continues as long asthe solar cell has sunlight striking itand it stops producing current flowas soon as the light is not strikingthe cell.Several other important facts toknow about solar cells are that thecells are also made with the P~typematerial on top and the N-type rna-terlal on the bottom and that there

!-IeS88SS,~8Solar Cell---- '-",~, ----,, I, /,/",holes

88888 8888888888

88


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EXPERIMENT 1Study the sample solar cell in the plas-tic box. Do not remove it from the box un-

less told to do so by your instructor. Wehave supplied this cell so that you will beable to see an actual individual solar cell.The cell that is in the box is an irregularshaped cell broken from a larger rectan-gular solar cell. A unique fact about solarcells is that no matter how odd shapedthey are, they will still produce electricity.Since one small solar cell produces verylittle current and voltage, it's not practicalfor use in powering useful devices. In Ex-periment 2 we will learn how solar panelsare made. Solar panels produce enoughpower to be used in thousands of appli-cations.As you look at the small solar cell you

should be able to identify the larger col-lection bar. Notice how the smaller collec-tion bars are connected to it. The bottom

surface of the cell is a silver plated surface;it is the second connection point for a com-plete circuit. Each individual silicon solarcell produces about .45V up to .55V of opencircuit voltage when it is placed in the sun-light, no matter what size it is. There areseveral factors that impact the current thata cel! will produce but in general the largerthe cell, the larger the amount of currentThe cell that you are looking at is knownas a polycrystalline cell and it has a blueanti-reflective surface.

Please complete the visual expedment Quiz below and inform yourinstructor aher you have completed It1) Identify the large collection bar and the smaller collection bars. What are theirpurposes?

2) Look at the anti-reflective coating on the top of the cell. What is its purpose?

3) Where would the probes of a meter be placed to measure the solar cells output?

4) This sample solar cell is small. What characteristic of the cell would be increasedif we had a larger cell? (A) Voltage or (8) Current


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As we learned in Experiment 1, an indi-vidual solar cell does not produce enoughenergy for many practical applications.Since a solar cell can only produce about.5V, we must connect many of them inseries to produce a useful voltage. Foreach cell that we connect in series we in-crease our output voltage by .5VDC. Whensolar cells are connected together in se-ries we call the assembly a solar panel orsolar module. Many different companieshave produced a variety of size and typesof these panels and we will describe themost common types. The type typicallyfound on rooftops for power generation aretypically made by starting out with a largealuminum base; then 36 cells are con-nected in series and placed on top of athin layer of clear flexible silicon coatingthat covers the aluminum surface. Moresilicon material is poured on top and thesolar panel is "cured" or baked. Thiscauses the silicon material to solidify intoa flexible encapsulant which surroundsand protects the entire assembly. Finally,a glass surface is molded onto the top andheavy duty screw terminals are mountedin the frame (for power takeoff).

current can be up to 4 amps or more. Thesepanels are sometimes connected in serieswith other like panels to form an array ca-pable of producing 50VDC @ 4 amps::::200watts of electricity. A battery array is some-times used to store energy for use at nightand an inverter is used to convert theSOVDC into 120VAC for use in the house.Another type of panel which is gainingpopularity is the amorphous glass solarpanel. This is more efficient to manufac-ture as it does not use individual cells handsoldered together in series like the abovementioned panel uses. Instead a very thinamount of silicon resin is deposited on glassin bands connected together by the pro-cess to form a solar panel. Each band rep-resents one solar cell. The glass panels aremore rugged than unmounted silicon solarcells and the process produces a lower costsolar panel. The main disadvantage of thinfilm technology is a slightly lower conver-sion efficiency. A comparison of typical effi-ciencies is shown below:

6-7%11-14%12-15%

The output voltage on these panels is typi-cally 18 to 22VDC open circuit and the

Amorphous SiliconPolycrystallineSingle Crystal

The solar pane! included with your kit is ahigh output amorphous silicon glass panel.It has 2 leads: positive (+) red and nega-tive (-) black. If it is not physically damagedor dropped on a hard surface it will last foryears and years. This panel producesenough power to power a small motor,power electronic circuitry or even chargeup a rechargeable battery. Amorphous sili-con glass panels have a current output re-lated to their size. If a panel was two timesas large we would expect twice as muchcurrent but the same voltage output. Pan-els such as this one but much larger areused even at remote cabins to provide elec-tricity where none would be available. The


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film that has been deposited on the glassforms individual solar cells. Each cell isconnected in series with the next one andthe power is supplied to the two colorcoded leads. The leads are attached atthe factory by first removing a smallamount of the thin insulating surface. Thisexposes a layer of very thin aluminum film.A special alloy zinc/aluminum solder isused to attach the wire to the panel andeach connection is then sealed in epoxyfor mechanical strength.

High Output AmorphousSilicon Solar Panel

QUIZ1) On your solar panel, measure the size of an individual cell (band). How many of thesecells are connected together on your panel?

2) The bands or cells are connected in: (A) Series or (8) Parallel?

3) If your instructor has a digital or analog meter measure the voltage in full sunshine.What is it?

_____ Volts DC and Current~ _

4) If we had a panel that was 2 times as large as this one but had the same amount ofbands (cells) would the voltage or current change? If so, by how much?

5) If we had several of these panels and wanted to increase the voltage would we con-nect them in series or parallel?


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DIODE ACTIONA small device that is critical for practicalstorage of solar power is the diode. Whenthe diode was first discovered it was knownas the Edison effect. The diode changesAC current into DC current and since itconducts in only one direction it can alsoblock the flow of DC current This is thecharacteristic that makes the diode animportant part of solar technology. If a so-lar panel is connected directly to a fan orpump, the device will operate whenever

sunlight strikes the panel. A problem sur-faces when using solar panels to charge upa storage battery to allow a fan, pump, mo-tor, light, etc. to operate at night. What hap-pens is that when darkness comes the en-ergy stored in the battery flows backwardsthrough the solar panel and eventually dis-charges all the energy that was stored dur-ing the daytime so that whatever useful light-jng or pumping etc. does not happen. Here'swhere the small semiconductor deviceknown as the diode comes into action. Thediode consists of a PN junction which startsto conduct electricity in the correct forwarddirection when the junction voltage is ex-ceeded (in the case of the 1N4001 includedin this kit it is .6 volts). Looking at our circuitin Fig. 1 we see that the diode (D1) is con-nected between the solar panel and themotor. If we connect up this circuit and placethe completed assembly in the sun weshould hear the motor run. i f the diode func-tions as we have stated we should be ableto turn it around and prevent the panel frompowering the motor,

1) Build the circuit shown in Figure 1 by carefullywiring the universal breadboard as shown inFigure 2. Connect the Solar Panel observingthe color polarity shown. Observe the location Spof the cathode band when installing 01.

3) Bring the assembly indoors and carefully turnthe diode around and insert it into thebreadboard. This time the cathode band of 01 should be connected to the red wire ofthe solar panel SP.

4) Carefully take the assembly into the sunlight. Did the motor shaft spin? If you con-nected the diode up as stated in Step 3 the motor will not receive current from the paneland will therefore not spin.

EXPERIMENT 3PROCEDURE 01anode cathode

2) Carefully take the assembly into the sunlight andyou should hear the shaft of the motor spin.

Motor

Figure 1


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Figure 2QUIZ1) What is the purpose of a diode used in conjunction with a solar panel and battery insolar electricity storage applications?

2) The motor used in this experiment could have been a battery that you wished to chargeup. If a battery was used, draw the correct symbol and cathode location of a diode inthe figure below:

SP ~'-_: ---'~: Storage Battery

3) What are the two parts of a diode known as?

4) When connecting a diode to a solar panel it will reduce the panels output voltage bythe amount of the junction voltage of the diode. What is this voltage for a silicon diode?


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SOLAR POWERED DC MOTORIn this experiment we will demonstrate thateven a small solar panel can power a DCmotor. One of the most important applica-tions of free solar energy conversion toelectricity is the pumping of water in re-mote locations throughout the world. Forefficiency, price considerations and reliabil-ity, these water pumping systems utilize apowerful, reliable DC water pump and areliable maintenance free solar panel. ADC pump is simply a DC motor connectedto an impeller that rotates and moves thewater.

+ W ate r is p um pe d o ut h ereCutawayView"

of a soft iron cylindrical shaped case. Onemagnet has a north seeking pole for itsface and the opposing magnet will havea south seeking magnet face (facing thenorth seeking magnet face). The shaft onthe motor is assembled to a core calledan armature. The armature core is madeup of slotted iron plates glued together.Around the armature are many windingsof wire making up typically 3 separateelectromagnets (some DC motors have 6or even more). The armature also has aset of 6 contact points called the commu-tator. Three electromagnetic wire coils onthe armature are connected to these con-tacts (two contacts are needed for eachelectromagnet coil).

connects to impellerI mp e ll er i ns id e r ot at esa nd cau se s w ater tobe p u m p e d out

W ate r g oe s in h er eDC water pumps use a DC motor so weneed to learn how a DC motor works. AllDC motors work basically the same way.These types of motors find use in somecars for operating windows, battery pow-ered tape recorders, toy cars, DC fans, etc.Typically the small DC motor will use twocurved shaped permanent magnets inside

C A S EP E R M A N E N TM A G N E T S


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The DC power from the solar panel thatcauses the shaft to move is brought intothese electromagnets by carbon brushesthat touch the commutator. As power isbrought into the different electromagnetsthrough the brushes and commutator theshaft rotates. This occurs because thecoils have been wound in a way that inconjunction with the commutator, the elec-tromagnet forces reacting with the twopermanent magnetfields changes continu-ously. The constantly changing magnetic

fields causes the armature to rotate aslong as power is applied.In our experiment we will connect a redpropeller to our DC motor and make a fan.Obviously instead of a propeller the shaftwould be connected to an impeller if wewere making a water pump. The principlesof the DC motor operation are basicallythe same in each case.

EXPERIMENT 4 PROCEDURE1) Carefully install the red propeller onto themotor shaft (if it is not already installed) by sim-ply pushing it on.2) Build the circuit in Figure 1. Insert the motorstand into the universal breadboard as shownin Figure 2 (on next page). Make sure that allpins are inserted into the contacts of the bread-board.

SP Motor

Figure 1

3) Now use wires to connect over to the contact rows that the solar panel wire will beinserted.4) Connect up the solar panel with color polarity as shown and take the assembly into thesunshine.5) You should feel a breeze coming from the front of your fan as the propeller spins.6) Now take the assembly inside and reverse the color polarity leads of the solar panel.

7) Take the assembly outside in the sunlight. This time the propeller will spin but since theshaft is spinning in the opposite direction it does not "blow" air out The direction of thespinning propeller is the same as on a propeller driven airplane.8} The glass panel is very efficient Try shading part of the panel with your hand to see ifthe prop continues to spin. Solar water pumping systems are typically designed so thateven if a cloud blocks the sunlight, the motor will continue to run (at lower speeds).


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Figure 2

QUIZ1) What happens if you reverse the polarity of the voltage applied to a DC motor?

2) What do the brushes come into contact with inside the motor?

3) If a solar panel is shaded by a cloud will a DC motor still run?

4) Why are DC type motors used in most solar water pump systems?


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You should notice that the first color bandis brown. Decoding the color brown from

RESISTORS AND the Resistor Color Code Chart (in Fig. 2)COLOR CODE gives a 1. Next look at the second colorWorking with solar pow- band and notice that it is green. Decod-

ered DC circuits it is sometimes neces- ing this band gives a number 5. The thirdsary to limit solar power to prevent over- color band is orange which is the numbercharging of a battery. While sophisticated 3, however since the third band is thecontrollers are used in most larger sys- multiplier it shows that we should multiplyterns, a simple way of limiting the output the first 2 digits by 1,000. A simpler waypower of a solar panel is to use a device to decode the 3rd band is just to add theknown as a resistor. number that is decoded in the form of ze-A resistor is typically a two lead device in ros to the first two digits. In this case itwhich carbon film or granules have been would be 15 + 000 or 15,000 = 15K.enclosed in an epoxy case. Depending on The fourth band is the tolerance which canthe mixture of carbon that the manufac- be gold = 5%, silver = 10% or no band =turer uses, different values can be pro- 20%. The tolerance isthe amount that theduced. The unit of resistance is known as resistance can vary from the valuethe ohm and resistor values are expressed marked. Resistors come in all shapes andin ohms (Q), kilo ohms (K), or megohms sizes depending on the type and power(M). A systems was developed years ago r;:jrRiithr;a;-tthie~y~c;.a~n~h~a;;nd;l;e~.-::-::-::--:::-":",","" JtllJto mark the value of the resistor. This mark- ..J ....Iing system is known as the Resistor Color fi:;";~An;-T~::;:-;:~-;:;::-~~:::-;;:::7:::~~:::""'=---HICode. Most common resistors are markedwith 3 or 4 color bands around the body.We will describe in this experiment how touse the color code and then we will useresistors in a solar circuitTo use the color code select a brown-green-orange resistor from the parts pack-age. Hold it in your hand orienting it sothat the band that is closest to the resistormetal lead is next to your index finger andthumb (see Fig. 1).

BLACKBROWNREDORANGYELLOWGREENBLUEVIOLETGRAYWHITE

1.10.1001,000 (K)10,000100,000.1,000,000. (M)10,000,000.100,000,000.000

r~-jGREEN ORANGE GOLDt ~ t5 000 5%J J I I

BROWNt1I


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PROCEDURE1) Select a 12 ohm resistor (brown, red, black) from the parts package, the motor withpropeller, the solar panel, the universal breadboard and wires. Connect up the circuitshown in Fig. 4 by wiring the universal breadboard as shown in Fig. 5.2) Take the assembly into the sunshine and the propeller should spin. Shade the panelfrom the sun momentarily with your hand and when you remove the shade the propellershould start to spin again. Now bring the assembly back inside.3 ) Change the 12Q resistor to the 1 K resistor (brown, black, red). Now we will observethe effect of placing a resistor of about 9 times the amount of the 12Q resistor on thecircuit. Take the assembly outside into the sunshine. The propeller will not spin byitself, however if you give it a spin in the correct direction it will continue to spin. Tryshading the panel with your hand and you'll notice that the propeller will not restartby itself like it did with the 12Q resistor. Bring the assembly inside.4) If you wish you may replace the 1 K resistor with the 1 5K resistor (brown, green, orange)and take the assembly into the sunshine. This time, no matter how much you try tostart the propeller spinning it will not run by itself. The resistance has reduced theoutput of the panel reaching the motor to a very tiny amount.

Resistor

SP

Figure 4

CS, INC.


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Figure 5

QUIZ1) What is the color code for a 18,OOOQ(18K) 5% tolerance resistor?

2) What is the value of a green, brown, orange resistor?

3) What is the tolerance for a resistor which has a silver colored 4th band?

4) Why is it sometimes necessary to place a resistor in series with one of the solar panelleads when the panel is being used to charge a battery?


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SOLAR POWERED ALARMSolar power can also be used to performother functions besides just spinning apropeller, pumping water or lighting a lamp.In this experiment we will use our solarpanel and an electronic buzzer to provideus with a solar powered alarm. The alarmcould be placed in a window ledge in yourhouse and it would provide a loud tone towake you in the morning. The alarm couldbe placed anywhere in a room as long as

sunshine is allowed to strike the panel.The electronic buzzer has a complete elec-tronic circuit inside its case. It uses a tran-sistor and a piezoelectric disc to emit a highpitched tone whenever voltage of the cor-rect polarity is connected to its terminals.We don't need to study the internal circuitryof the buzzer since it is sealed inside thecase. Other possible uses of the alarmcould be to alert you by a difference in tonevolume whenever the sky was overcastThis fact would be important if you had afarm and were relying on a solar pane! op-erated water pumping system for crops orlivestock.

PROCEDURE1) Connect up the circuit shown in Fig. 1 using the elec-tronic buzzer, the solar panel and 2 wires as shown inFig. 4. Note: the polarity of the buzzer must be observed, Sphowever the solar panel included in this kit will not dam-age the buzzer if you do not observe the polarity but itwon't work unless you have it correct. Take the assemblyoutside into the sunshine and you should hear a loud highpitched tone. Place your hand over the panel and you L_ F _ ' _ g _ u _ r e _ 1 ---r....,-~i4should still hear a tone from the electronic buzzer. Bring ....- ....,- Ld:t!the assembly back inside. 15K2) The loud sound would almost be too much to deal withearly in the morning so let's try to tone it down. Leave theelectronic buzzer and panel connected to the breadboard, SPhowever replace one wire with the 15KQ resistor (brown,green, orange). See Fig. 2 and Fig. 5. Take the assem-bly back into the sunshine and this time the tone shouldnot be as loud. Bring the assembly back in. Figure 2

+BZ1

BZ1

3) Another even more basic way of reducing the volumeis to cover up part of the solar panel. Connect up theoriginal circuit from Step 1. Cut off a piece of constructionpaper, cardboard, etc. the same size as the solar panel.Take this paper and the assembly outside and place inthe sunshine. See how much of the panel can be cov-ered up and still have the electronic buzzer produce atone. Note: cover it up along the length, see Fig. 3.


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I Figure 4 1

I Figure 5 1

QUIZ1) When you covered up part of the panel which solar panel attribute did you effect themost: The panel's current output or voltage output?2) What is the electronic device used to reduce the panel's output?3) Why must the polarity be observed on the electronic buzzer?4) What fact is apparent concerning the generation of electricity from a solar panel vs. thebrightness of the sunshine?


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SOLAR POWERSTORAGEOne of the most commonproblems that must be

dealt with when using solar power is thefact that many times we need to use en-ergy at night when the sun doesn't shine.We have already learned that in darknessthe solar panel will not produce any elec-tricity. So what if our application is sound-ing a buzzer at night? In this experimentwe will study a simple method of storingthe suns energy for use at a later time.As mentioned before commercial rooftopsolar electrical systems typically charge upbatteries and these are used with a de-vice known as an inverter to convert thelower voltage battery DC potential to stan-dard 120VAC. In our experiment we willuse an electronic component known as a

super cap to store some of the electricitythat our solar panel produces. The supercap that is included in this kit is a recentdevelopment in the field of electronics. Al-though capacitors have been around foryears and years the super cap was devel-oped to retain memory information for com-puters. It is very small for its large value. Infact it is rated .022 Farad which makes itsimilar in current storing ability to a smallrechargeable battery. The difference is thatthe super cap can be recharged for almostan infinite number of times. A capacitor inits simplest form consists of two metallicplates that are close to each other but arenot touching. The material that separatesthe metallic plates is called a dielectric andcan be ceramic, air, mylar film, tantalum andeven a paste substance known as an elec-trolyte. We will use our electronic buzzer, aresistor, the super cap, the diode, the bread-board, solar panel and switch.

D1 R1

2) Take the assembly into the sunlight for about 2 minutes. After this time period haspassed depress the pushbutton and the buzzer should emit a soft but high pitched tone.Bring the assembly back inside,3) Now cover the panel with construction paper, cardboard or some other opaque paper.Leave the assembly alone for 10 more minutes. Now depress the button and you shouldhear the tone again indicating that the super capacitor stored the electricity from Step 2(since for the last 10 minutes the panel was covered and unable to produce electricity).4) You may wish to leave the panel covered up overnight and see if the super cap still hasenergy left in it the next day.

PROCEDURE1) Wire up the circuit shown in Fig 1using the 12~2 resistor (brown, red,black) for R1. Observe polarity on thesolar panel (red and black leads), thediode (cathode bandmust be at loca-tion shown), the super capacitor (the 2black stripes along the one edge indi-cates (-), and the electronic buzzer.

SP +C1,...-r-,

Figure 1


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Figure 2

QUIZ1) What besides a battery can store electrical energy?

2) What is the purpose of the diode in this circuit?

3) Even though the solar panel was not in the sunlight the buzzer sounded in Step 3.Why?

4) Do electrolytic capacitors such as the super capacitor have a polarity? Does a batteryhave a polarity?


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SOLAR POWEREDFLASHING LIGHTMost of the outdoor solar powered land-scape lights that are sold today consist ofa smail solar panel, a rechargeable bat-tery and a light emitting diode (LED). inthis experiment we will use our super capto store some of the electrical energy fromthe sun to power our special flashing LED.Light Emitting Diodes or LEOs are usedas indicators in thousands of electronicproducts and even as a source of light asin the outdoor landscape lights. The LEDconsists of a PN junction of special semi-conductor material that converts electricalcurrent directly into photons (light). Pho-

tons, current and PN junction serniconduc-tor material sounds a little familiar. As youhave probably guessed solar cells andLEOs have some terms in common. TheLED emits light in direct proportion to thecurrent flowing through it. It can be de-stroyed by allowing too much current to flowthrough it, but fortunately our solar panelwon't harm it The LED we will use in thisexperiment is special. It contains a built-inintegrated circuit (IC) to cause it to flashwhen current is applied. All LEOs requireDC current applied with the correct polarityto work. An LED has typically two leads:the anode (+ ) and the cathode (-). Thelandscape lights we referred to use an LEDfor their light source because they requiremuch less current to operate which is im-portant jf only a small solar panel is used.O f course a typical LED produces less lightthan the average incandescent lamp.

2) Take the assembly outside and expose thepanel to the sunshine for several minutes. Now Figure 1bring it back inside and depress the button onSW1. If you have connected the circuit up correctty the LED should begin to flash brightly.

PROCEDURE1) Connect up the circuit shown in Fig. 1 usingthe super cap, the pushbutton switch, the di-ode, the universal breadboard, the 12Q resis-tor, the solar panel and wire. Make sure to ob-serve polarity on the solar panel, super cap, dl-ode and LED.

D1 R1

_ . _ _ +C1P

3) As we stated earlier LEOs have a polarity. Remove the LED and turn it 1800and thenreinsert it into the breadboard so that the cathode and anode are reversed. Now press thebutton. This time the LED will not flash. Remove the LED and reinsert it correctly. Test it bypressing the button on the switch. There should be enough power to cause the LED to flashagain.4) Another interesting experiment is to hold the button down until the LED no longer flashes.Now release the switch button and leave the panel and assembly inside under just the roomlight After about 30 minutes, depress the switch button and the LED should flash again.This shows that even ambient room light isconverted into electricity by the small solar panel,


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Figure 2

QUIZ1) Why are LEOs commonly used in solar powered landscape lights?

2) What is used to make an LED?

3) Do LEOs have a polarity?

4) Do solar panels need to be exposed to direct sunlight to produce electricity?


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SOLARPULSATING ALARMNow that you have experience with vari-ous electronic devices and the solar panel,it's time to put this knowledge together tobuild a more complex device. In this ex-periment we will use the flashing LED, theSolar Panel, diode, resistor, flashing LED,the solar panel, diode, resistor, flashing

LED and universal breadboard to make aunique sounding pulsating alarm. Nowwhenever sunlight strikes the solar panel,our circuit will cause an electronic buzzerto produce a pulsating tone.Engineers are challenged all of the time todevelop products that meet a special need.Most of the time there are constraintsplaced on them for the design. It might bethat the device to be designed must be lowcost, or it must be very efficient (uses asmall amount of current), or maybe thecompany just wants to use existing com-mon parts. Our particular pulsating alarmmeets all of the above design rules.

PROCEDURE1)Following Fig. 4 , use the breadboard, 120.resistor, diode, electronic buzzer, wires andsolar panel to connect upthe circuit shown inFig. 1. Make sure that the polarity on all com-ponents (except for the resistor) is observed.

Figure 1

01 R1anode cathode

SP

2) Take the assembly into the sunlight andlisten to the pulsating alarm. Bring the as-sembly inside and it will be silent

01 R1) What ifwe wanted to view the flashing LEDand hear the pulsating alarm at the sametime? That's no problem for an engineer ordesigner. We will just add our storage ca-pacltor, Add the super capacitor with polarityas shown in Fig. 2 (See Fig. 5 for where the SPsuper capacitor goes on the breadboard).Take the assembly outside in the sunlight andleave it for about a minute. Bring it back in-side and you should hear the alarm pulsateand the LED flash. This can go on for sometime, so you may wish to disconnect thesupercap i f you get tired of hearing the alarm.

anode

+C1

Figure 2L1~cathode

4) The flashing LED can even be used to cause the propellerto make short intermittent movements. Connect up the circuitshown in Fig 3 as shown by Fig. 6. Make sure that the correctpolarity is observed on the panel and flashing LED L1. Takethe assembly out into bright sunlight and the propeller shouldmove in short intermittent turns.

SP Motor

Figure 3


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BlackMake sure that

Cathode goes hereAnode-(LongerLead)

---Cathode(Shorter Lead)

L 1 Figure 4

BZ1


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Cathode (short lead) Ir,+"iiImust go here

Figure 6QUIZ1) What causes the electronic buzzer to produce a pulsating tone?

2) If we wanted to manually control when the pulsating alarm would sound, what compo-nent would we use?

3) Would the circuit shown in Fig. 1 work if we replaced D1 with a wire?

4) Would the circuit shown in Fig. 2 work as stated in step 3 if we removed the supercap? Why?


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ANOTHERENVIRONMENTALL YSAFE METHOD OFGENERATING POWERIn this experiment we will focus on anotherenvironmentally safe method of generat-ing power. Of course solar power gen-eration is a great way to generate elec-tricity, but another great way is from wind.Perhaps you have seen a farm house witha wind powered generator or have passedthrough the extensive "wind farm" locatedin the California desert along Interstate 10near Indio.It turns out that when the shaft of a DCmotor is turned, electricity is produced. Inthis experiment we will generate a small

amount of this ''free power" by manuallyturning the propeller attached to the mo-tor. Various electronic radios, flashlightsand lanterns are sold today that have asmall crank and a DC generator (a DCmotor basically) to produce the power foroperation. We will store the electricity pro-duced by our generator/motor in the su-per capacitor. To prevent the capacitorfrom draining all of the charge back intothe generator/motor we will use a diode.Large generators connected to the largeprops at wind farms can produce enoughelectricity to power many houses. Theonly requirement is a good constant flow-ing wind. Compared to solar panels, thewind generators continue to work even oncloudy days, however, when the windstops so does the power. That is whysome people use both sources of powergeneration in remote areas. Obviouslysometimes the wind will blow aUnight longand solar panels are useless at night.

2) Spin the propeller in the clockwise direction as fast as you can using your index finger.Don't tr y to hold onto the propeller-just try to spin it. Repeat the process about 10 times.3) Depress the button on SW1 and you should hear a tone from the buzzer. The buzzer isemitting the tone because of the electricity you generated by spinning the propeller.4) Replace the buzzer with the flashing LED, see Fig. 3. Make sure that the anode lead ofthe LED goes to the switch and the cathode of the LED (shorter lead) goes to the (-) leadof the super cap. Spin the propeller about 10 times and depress the button on SW1. TheLED should flash faintly.

PROCEDURE1) Connect up the circuit shown in Fig. 1 us-ing the pushbutton switch, the motor withprop, the electronic buzzer, the diode, thesuper cap, and the universal breadboard.See Fig. 2 for correct placement of parts inthe breadboard. Make sure to observe po-larities and mount motor exactly as shown.

+cathode

+C1

Figure 1

SW1

BZ1


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Figure 2

L1Anode(Longeread)

1 2 3 4 5

9

dc

Figure 3

NC.


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QUIZ1) Does our motor/generator have a polarity?

2) How could this polarity be reversed?

3) in ''wind farm" applications, regulators are used to control the output power. Why?

4) Could we store the electricity that we generated without the diode? Why?

The End

laborator 8 celule fotovoltaice si aplicatii

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