Introduction electronic circuits will allow evaluating whether or

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Last updated: April 16, 2019

Introduction A basic understanding of electronic circuits is important even if thedesigner does not intend to become a proficient electrical engineer.

In manyreal-life engineering projects, it is often necessary to communicate, and alsonegotiate, specifications between engineering teams having different areas ofexpertise. Therefore, a basic understanding of electronic circuits will allow evaluatingwhether or not a given electrical specification is reasonable and feasibleElectronics is a know how of how to manage electrical energy. It dealswith electrical circuits and components like transistors, diode, resistors,capacitors, amplifiers and integrated circuits. In an MFC project it is of prime importance to consider the study ofelectronics as it has a major role to play.

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A study to understand the basicelectronics components, it implementation and circuit designs is deemed to beable to make optimal and reap maximum benefits.  In the following discussion,the basic components of electronics and itsimplementation will be discussed.  Resistors An electrical component to create resistance in electric current iscalled is Resistor.The resistance value and tolerance are indicated with several coloredbands around the component body.   Fixed resistor symbolANSI standard Fixed resistor symbol  Resistor color codeTo determine the amount or magnitudeof the electrical current flowing around an electrical or electronic circuit,we need to use certain laws or rules that allow us to write down these currentsin the form of an equation.

The network equations used are those according toKirchhoff’s laws, and as we are dealing with circuit currents, we will belooking at Kirchhoff’s current law, (KCL).   Resistorwith a resistance of 5600 ohm with 2 % tolerance, according to the marking codeIEC 60062.Effect ofTemperature on ResistanceChange in temperature causes the resistance to change. This may happenbecause temperature changes the dimension of a conductor. Also wires with highthickness have less resistance and vice versa.

  Resistors in Parallel Let’slook how we could apply Kirchhoff’s current law to resistors in parallel,whether the resistances in those branches are equal or unequal. Consider thefollowing circuit diagram:  In this simple parallel resistorexample there are two distinct junctions for current. Kirchhoff’s First Law Asper Kirchhoff’s law the charge entering a node is equal to the charge leavingthe node and the total current is zero. There is no loss of current. Kirchhoff’s Current Law A junction or a connection of two or more currentcarrying routes like cables and other components is called as Node.

Parallelcircuits can also be analyzed by Kirchhoff’s current law.  In the above figure, the currents I1, I2 andI3 are entering the node are positive and two currents I4 andI5 are negative. This can be expressed as:I1 + I2 + I3 – I4 – I5 = 0 Kirchhoff’s Second Law In any closed network the sum of voltage is equal tozero if we do an algebraic summation of all the voltage across each loop. Kirchhoff’s Voltage Law Wecan begin from one point of the loop and continue in the same direction,clockwise or anti clock wise.   Thefinal voltage value will not be zero if the direction is not maintained. It hasto either clockwise or counter clock wise.

Weneed to be clear with all  the terms likenodes, loops etc so that we can understand it for the AC and DC circuitanalyses base on Kirchhoff’s Current Law. Superposition Theorem:The total current in any part of linear bilateralcircuit can be calculated by evaluating the separate current by open circuitingthe current source and short circuiting the voltage source and summing them tocalculate the total current.   Thevenin’s Theorem A two terminal combination of batteryand resistance can be replaced by a single current source and voltage sourceacross the terminals.

  Norton’s TheoremA twoterminal collection of resistance and battery can be considered to be equivalentto an ideal current source in parallel arrangement with a resistor. The valueof current can be derived by diving the voltage by r, where r’s value is sameas Thevenin’s equivalent. CapacitorCapacitorcomponentsA capacitor is designed by sandwiching an insulatingmaterial between two metal plates. The insulation material in between is calleddielectric.The dielectric ensure there is not physical contact between themetal plates. Any material which is impede the flowof current can be used as a dielectric. For ex; glass, plastic, rubber, paperetcA capacitors capacitance depends onhow it has be constructed. More the surface are overlap, more is thecapacitance value, but lesser distance results into higher capacitance.

Largecapacitors have higher capacitance value.Below is the equation for totalcapacitance  In the above equation ?r is thedielectric’s permittivity, d is the distance between the capacitor plates and Ais the area of the plates which overlap.Charging and DischargingAcapacitor is said to be charged when the positive and negative chargedaccumulate on each plate, but could not meet as they are separated by aninsulator. At some point the plates become fully charged and hence cannot accept anymore charge. This is the maximum amount of charge a capacitor can hold.If a path is created in the circuitthrough which it could dissipate it discharges the capacitor and is called as dischargingof capacitor. Calculating Charge, Voltage,and CurrentThe potential difference between theplates determines how much charge can be stored in a capacitor.

The equation todepict the same is V is the voltage applied, Q is the Charge store and C isthe capacitance.One Farad can be defined as the capacity to store oneunit of energy per one voltFeatures of CapacitorsDifferent types of capacitors havedifferent utilityWhen deciding on capacitor types thereare a handful of factors to consider:Size –Physical andCapacitance.Maximum voltage –Eachcapacitor has a voltage rating for ex 1.5 V. Exceeding it could be a destroyit.Leakage current -. Everycapacitor leaks small amount of current through the dielectric. It is called leakage.

Equivalent series resistance (ESR) –Theresistance provided by the terminals of capacitor is called Equivalentresistance. It is usually very small.Tolerance –All capacitorsmight vary from the ideal defined capacitance which could be from 1% to 20 % CeramicCapacitorsThis is one of the most commonly usedand produced capacitor. The name has been derived from the material from whichtheir dielectric is made.Ceramic capacitors are usually small bothphysically and capacitance-wise. Ceramic capacitor much larger than 10µF ishard to find.

Two caps in athrough-hole, radial package; a 22pF cap on the left, and a 0.1µF on the right.In the middle, a tiny 0.1µF 0603 surface-mount cap.Compared to the popular electrolyticcapacitors, ceramics are a more near-ideal capacitor (much lower ESR andleakage currents), but their small capacitance is a limitation. Aluminum and Tantalum ElectrolyticThese type of capacitors are good for high voltageapplications and they have a high capacitance and are relatively small. Itranges from 1µF-1mF.It looks like a tin can with two leads at the bottom.

An assortment ofthrough-hole and surface-mount electrolytic capacitors. Notice each has somemethod for marking the cathode (negative lead).SupercapacitorsThese are uniquely made to store veryhigh capacitance. A 1Fsupercapacitor.High capacitance, but only rated for 2.5V. Notice these are also polarized.These capacitors have very highcapacitance, but have relatively low voltage.

A high voltage rating is achievedarranging them in series. Capacitors in Series/ParallelMultiple capacitors can be combinedin seriesor parallel to create a combined equivalent capacitance. Capacitors,add together in a way that’s completely the opposite ofresistors.

Capacitors in ParallelThe total capacitance of capacitors inparalleled is the  sum of all capacitances. This is analogous to the way resistors add when they are inseries. For example, if you had threecapacitors of values 10µF, 1µF, and 0.1µF in parallel, the total capacitancewould be 11.

1µF (10+1+0.1).Capacitors in SeriesSimilar to resistors in parallel, thetotal capacitance of Ncapacitors in series is the inverse of thesum of all inverse capacitances. If you only have two capacitorsin series, you can use the “product-over-sum” method to calculate the totalcapacitance: Capacitor Colour Code Table Band Colour Digit A Digit B Multiplier D Tolerance (T) > 10pf Tolerance (T) < 10pf Temperature Coefficient (TC) Black 0 0 x1 ± 20% ± 2.

0pF Brown 1 1 x10 ± 1% ± 0.1pF -33×10-6 Red 2 2 x100 ± 2% ± 0.25pF -75×10-6 Orange 3 3 x1,000 ± 3% -150×10-6 Yellow 4 4 x10,000 ± 4% -220×10-6 Green 5 5 x100,000 ± 5% ± 0.

5pF -330×10-6 Blue 6 6 x1,000,000 -470×10-6 Violet 7 7 -750×10-6 Grey 8 8 x0.01 +80%,-20% White 9 9 x0.1 ± 10% ± 1.0pF Gold x0.

1 ± 5% Silver x0.01 ± 10% Metalised Polyester Capacitor              Usually the capacitors have 2-3number and an optional tolerance letter code The two numbers is used todetermine the value of the capacitor and is in picofarads. The third lettercode is multiplier similar as resistors. For example, the digits 531 =53´10 = 530pF. Three digit codes areoften accompanied by an additional tolerance letter code as given below.

Capacitor Tolerance Letter CodesTable Letter B C D F G J K M Z  Tolerance= C<10pF±pFDiode Unidirectional flow of current occurred due to adiode which is functional in rated specific voltage intensity. The mainfunction of diode is to oppose current in opposite direction. Thevoltage at which it breaks is known as reverse breakdown voltage. Rectifier Alternating Current (AC) is exchanged into a DirectCurrent (DC) through a rectifier which is an electrical device and use one ormore P-N junction diodes with precise array.

The forward bias is when positive terminal connect withP-type and negative terminal connect with N-type and voltage is given to theP-N junction. When P-type is joined with –ve terminal and N – typeis joined with +ve terminal and the voltage is applied to the P-N junctiondiode, it is called reverse bias. Rectifier types: Half wave rectifier Full wave rectifier Bridge rectifierHalf wave rectifierThe rectifier which converts half of the AC inputsignal (positive half cycle) into DC output signal and the remaining halfsignal (negative half cycle) is  lost isknown as half wave rectifier. In half wave rectifier circuit, only one diode isused.

Full wave rectifierThe fullwave rectifier transfer the full AC input signal(positive half cycle and negative half cycle) to pulsating DC output signal.The efficiency of full wave rectifier is high as compared to the half waverectifier.Bridge rectifier Alternating Current (AC) converted into DirectCurrent (DC) proficiently through Bridge rectifier which utilizes four ormore diodes forcircuit design. In this configuration it converts the full AC input signal intopulsating DC.Bridge rectifier constructionBelow is the construction of bridge rectifier.

AlternatingCurrent (AC) convert into Direct Current (DC) current by connection of four diodesin a closed loop in bridge rectifier. The benefit of the bridge rectifierconfiguration is so as to, it does not need an expensive center tappedtransformer. Hence it reduces the cost and size. Functional properties of bridge rectifier When input AC signal is applied across the bridgerectifier, positive diodes D1 and D3 are arrangedin forward biased and thus permit electric current to flow, but diodes D2 andD4 are oppose flow of electric current as they are arranged in reversebiased. During the negative half cycle diodes just opposite was happened. Fromthe above two figures, we can observe that the flow of current direction acrossload resistor RL is same during the both half cycles.Therefore, the polarity of the output DC signal is same for both positive andnegative half cycles. .

Bipolar TransistorWhen two PN-Junction diodes are connected in series, either a P-Type orN-Type material gets sandwiched. This creates three terminal, two junctiondevice called Bipolar Junction Transistor BJT. Transfer and Varistor combines to create the word Transistor. It describes their mode of operation intheir early days of electronics development. The two types of BJT PNP and NPN arebased on the physical arrangement of the semiconductor material p-type andn-type.It has two PN junction and three terminals Emitter, Base and Collector.It controls thecurrent flowing through it and are current regulating devices.

The current flowis proportional to the biasing voltage applied to the base terminal. Theworking of both types of transistors PNP and NPN are same and they only differon how they are biased.Bipolar Transistor ConstructionThe circuit arrangement for both the PNP and NPN aregiven below. Same as diode the direction of the arrow is same fromP-type region to N-Type.Bipolar Transistor ConfigurationsAs we know it is threeterminal device all the three terminals are connected in an electronic circuitdifferently where one terminal is common between the other two and hence namedas. Common Base Configuration (CB)  –   This setup has Voltage Gain but no Current Gain.

Common Emitter Configuration  (CE) –  In this configuration the circuit has both the  Current and Voltage Gain. Common Collector Configuration  (CC) – Opposite to CB configuration it has Current gain, but no voltage gain.The Common Base (CB) ConfigurationIn this setup the base terminal is common and theinput is provide from the base and emitter terminal, whereas the output is themeasured from base and collector. The Common Base Transistor CircuitThe CB is a voltage amplifier with a non-invertingoutput. In this type of set-up the phase of the input and output voltage aresame. This is not very less likely used configuration due to the high voltagegain.

Common Base Voltage GainA common use of the this circuit is in microphone orradio device due to its high frequency response. In the above formulae Ic/Ie is the current gain,alpha ( ? ) and RL/Rin is the resistance gain.The Common Emitter (CE) ConfigurationIn a CE configuration theemitter terminal is common between the base and collector. The input signal isapplied through the base and emitter whereas the output is measured throughcollector and emitter terminals. Due to its moderate voltage and current gainproperties it is more used in the different electrical circuits.Transistor BiasingIf a transistor is tooperate as a linear amplifier it has to be biased to have a suitable operatinggain.

The operation of a transistor can be controlled by the base current, collectorvoltage and collector current Fixed Base Biasing a TransistorWhen the IB remains contact for a givenvalue of Vcc it is called fixed bias. Transistor Biasing with Emitter FeedbackWhen a transistor circuit isthe set up in a way that it uses both base collector and emitter has feedbackto stabilize the collector current is said to be in Emitter feedbackconfiguration. Voltage Divider Transistor BiasingA setup to use voltagedivider network to stabilize in the CE configuration is called Voltage Divider.As we can see in the above image that the two Resistors Rb1 and Rb2 are forms avoltage divider network across the supply. Operational Amplifier A set-up to amplify DC/ACsignals and performing operations like add, subtract, integrate, differentiateis operational amplifiers.

It is a linear device. The Summing AmplifierAn OP-AMP to derived asingle output voltage by summing multiple voltage inputs a summing amplifier isdesigned. Application of Electrical/ Electronic components inMicrobial Fuel Cell (MFC)One of the limitations forapplication of MFC system is low voltage output. Apart from environmental andmicrobial parameters affecting performance of MFC, certain changes inelectronic component may also help to improve voltage output where circuitdesigns can be modified (Meehan et al., 2011). Capacitors (Dewan et al., 2010),resistors, transistors, DC-DC converter are some electronic components whichmay help for electricity storage as well as boosting (Wang et al., 2015).

  By building large MFC, i.e. only increase insize will not improve power generation (Park and Ren, 2012). Modification inexternal resistance (R), known as load may also be helpful for higherelectricity generation and greater COD (Chemical Oxygen Demand) reduction (Liuet. al., 2006).

The current generated from MFC could be optimized and amplified with thehelp of Operational Amplifier (Walker, 1987). It can further be consumed by theBoost converter ((Parkand Ren, 2012)) and Buck Boostconverter. MFC with boost converterMFC could be connected as an input to boost converter and expected outputfrom boost converter is 1.

2 volt.MFC circuits can be integrated in series andparallel to achieve higher current and voltage output. As shown in below figurewhen MFC is connected in series, the resultant output should be summation ofindividual volt of MFC. In this Figure, four MFC could be connected in serieswhich should produce approximately 2.

4 V which is given to DC-DC converter forfurther boosting of voltage. Boost converter (DC-DC converter) with seriesconnected MFC ConclusionA microbial fuel cell (MFC) is capable of powering an electronic deviceif we store the energy in anexternal storage device, such as a capacitor, anddispense that energy intermittently in bursts of high powerwhen needed.Therefore its performance needs to be evaluated using an energy-storingdevicesuch as a capacitor which can be charged and discharged rather than otherevaluation techniques, such ascontinuous energy dissipation through a resistor.Studiedthe basic to electronics to integrate with MFC to generate current, and furtherintegrate it with electrical circuits to convert, amplify and stabilize the generatedelectricity into an electronic appliance usable format. 

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