LAB REPORT FOR LTSPICE PDF

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USING LTSPICE...

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Xavier University College of Engineering Electrical Engineering Department

Experiment No. 1

DC CIRCUITS

ACE 15 LA October 13, 2020

Group Members: (1) Hequilan, Mark James II (2) Lapuz, Jurgen Joseph (3) Mier, Vench Clark

Engr. Christine May Creayla

I.

Objectives

The following were the objectives of the experiment: 

The circuits were manually solved using the laws, theorems, concepts, and approaches in DC Circuits.



The circuits were simulated using LTspice software.



The values obtained from manual solving and LTspice simulation were compared and analyzed.

II.

Introductory Inf Infor or ormation mation Direct Current (DC) is the constant flow of electric charge from high to low potential. A

direct current circuit is a circuit in which electric current flows through in one direction. A DC electrical circuit consists of a source of DC electricity with a conducting wire going from one of the source terminals to a set of electrical devices and then back to the other terminal, in a complete circuit. The electricity moving through a wire or other conductor consists of its voltage (V), current (I) and resistance (R). Voltage is the potential energy which causes the electrons to flow, current is the number of electrons flowing through the wire, and resistance is the property of the electric circuit which opposes the flow of current. The units of voltage, current and resistance are volt (V), ampere (A) and ohm (Ω) respectively. All DC circuit analysis (the determining of currents, voltages and resistances throughout a circuit) can be done using the following laws: 1. Ohm's law. This law states that the current in a circuit is directly proportional to the potential difference across the circuit and inversely proportional to the resistance in the circuit. Mathematically, this can be expressed as

This law means that as voltage increases, current increases whereas as resistance increases, current decreases. This law can be applied to an entire circuit or parts of a circuit. Power, (P) in a circuit is the rate at which energy is absorbed or produced within a circuit. It can be expressed using the formula

P=I × V Ohm’s law can be used to correlate the equation with resistance (R)

P=I × V =

2 V2 I = R R

When using this formula, the unit of measurement for power is the watt (W). In other terms, it is a measure of how much work can be performed in a given amount of time. Components of an electrical circuit can be connected in series, parallel, or a combination of the two. Components connected in series are connected along a single conductive path, so the same current flows through all the components but voltage is dropped (lost) across each of the resistances. In a series circuit, the sum of the voltages consumed by each individual resistance is equal to the source voltage. For a series connection,

I =I 1 ¿ I 2 =I 3 =.. .

V =V 1 + V 2 + V 3 +. . . IR = IR1 + IR2 + IR 3+ .. .

R=R 1+ R 2+ R3 +. . . Components connected in parallel are connected along multiple paths so that the current can split up. In this case, voltage across each resistance will be same but current will be different depending upon the value of the individual resistance. For components connected in parallel, the following equations are used:

V =V 1= V 2=V 3=. . .

I =I 1 + I 2+I 3=. . . V V V V = + + +. . . R R1 R2 R3

1 1 1 1 = + + +. . . R R1 R2 R 3 Resistances in parallel circuit can also be calculated by the equation below

R R 1 R ¿ ¿ (¿ 2 )+( ¿ 2 R 3 )+( R 3 R1 ) ¿ R R R R1 R 2 ∨R= 1 2 3 R= ¿ R 1 + R2 In a given combination of resistors (series, parallel, or combination of series/ parallel), the equivalent resistance is that value of resistance, which when replaced in place of the combination, will continue to give the same performance for the part of circuit outside this combination. Equivalent resistance is nothing but the total resistance in the system being considered. 2. Kirchhoff’s current law. This law states that the algebraic sum of all currents at a node (junction point) is zero. Currents coming into a node are considered negative and currents leaving a node are considered positive.

I4 I3 I5 I2

I1

∑ Currents entering = Σ Currents leaving I1 + I3 = I2 + I4 + I5

3. Kirchhoff’s voltage law. This law states that the algebraic sum of all the changes in potential (voltages) around a loop must equal zero. A potential difference is

considered negative if the potential is getting smaller in the direction of the current flow. ΣE rise – ΣIR drops = 0 (around closed loop) ΣE = ΣIR Σ Potential rises = Σ Potential drops SPICE (Simulation Program with Integrated Circuit Emphasis) is a general-purpose, open source analog electronic circuit simulator. It is a program used in integrated circuit and boardlevel design to check the integrity of circuit designs and to predict circuit behavior. LTspice is a high-performance SPICE simulator, schematic capture and waveform viewer with enhancements and models for easing the simulation of switching regulators. The enhancements to SPICE have made simulating switching regulators extremely fast compared to normal SPICE simulators, allowing the user to view waveforms for most switching regulators in just a few minutes.

III.

IV IV..

Materials 

Computer with Windows or Mac OS



LTspice Software

Pr Procedures ocedures In this activity, the concept DC circuit shall be demonstrated. The different components

in a DC circuit was determined by both manual calculation and the use of a simulation software. The activity consisted of three parts. Each part was a circuit connection with various unknown variables such as the voltage and current. The following are the general procedures for the experiment: 1. Hand Calculation for solving the required values. 2. Open LTspice software and create a new schematic. 3. Assemble the circuit by adding components and connecting using wires. 4. Set the given values to each component. 5. Put a ground at any node. 6. Run the simulation by 1 millisecond. 7. Use the probe to determine the current across each component.

8. Compare the results with the values obtained from manual calculations.

V.

Data and R Results esults PART A Circuit A

Figure 1. Circuit A Hand Calculation

Figure 2. Simulation of Circuit A in LTspice

a

b

Figure 3. LTspice simulation results of Circuit A using a) Transient Analysis and b) DC Operating Point

Table 1. Comparison of Results between Calculation by hand and LTspice simulation (Circuit A)

Circuit A

Hand

3V

0.01A

0.0025A

0.0075A

3V

0.01A

0.0025A

0.0075A

Calculation LTspice Simulation

CIRCUIT B

Figure 4. Circuit A Hand Calculation

Figure 5. Simulation of Circuit B in LTspice

a

b

Figure 6. LTspice simulation results of Circuit B using a) Transient Analysis and b) DC Operating Point

Table 2. Comparison of Results between Calculation by hand and LTspice simulation (Circuit B)

Circuit A

Hand

3V

0.015A

0.01A

0.01A

3V

0.015A

0.01A

0.01A

Calculation LTspice Simulation

PAR ART TB Circuit C

Figure 7. Circuit C Hand Calculation

Figure 8. Simulation of Circuit C in LTspice

a

b

Figure 9. LTspice simulation results using a) Transient Analysis and b) DC Operating Point

Table 3. Comparison of Results between Calculation by hand and LTspice simulation (Circuit C)

Methods of Calculation

Equivalent Resistance (Ω)

Hand Calculation LTspice simulation

7.5 -

Percent Error

Circuit D

10 −5 io 7.5

0%

(Ω)

Figure 10. Circuit D Hand Calculation

Figure 11. Simulation of Circuit D in LTspice

Figure 2. LTspice simulation results of Circuit D using a) Transient Analysis and b) DC Operating Point

Table 4. Comparison of Results between Calculation by hand and LTspice simulation (Circuit D)

12 io

Methods of Calculation

Equivalent Resistance (Ω)

Hand Calculation

24.06

-

LTspice simulation

-

24.06

Percent Error

VI.

(Ω)

0%

Analysis and Conclusion

Hequilan: There are different ways of solving for the resistances, currents and voltages in a given circuit. One way of solving is through manual calculation in which careful analysis must be done so that appropriate circuit rules/laws and theorems will be applied. Another way of obtaining results is through simulation. This way it is easier and faster. In the experiment, LTspice simulation software was used to calculate for the unknown values. For Part B of the experiment, equations for solving resistances in series and parallel were used in order to calculate for the Equivalent resistance of the circuit. On the other side using LTspice, equivalent resistance is calculated by dividing the total voltage to the total current i o in which io is obtained by simulation. The obtained values of equivalent resistance for both manual calculations and LTspice simulation are the same with a percent error of 0%. This simply implies that LTspice software is a good application for simulating circuits in which accurate results are obtained. It can also be observed that the obtained values for currents has negative signs which signifies that the reference direction of the currents for LTspice is towards the negative side of the battery. On the other hand, the manual calculation assumed that by convention, the reference direction of the current must be towards the increasing potential. Lapuz: LTspice simulation software can calculate unknown currents and voltages around the circuit, the same as in manual calculation. By comparing the results of manual calculation and LTspice simulation (see table 1 and 2), they are the same for about 0% error. However, LTspice simulation and manual calculation have differences. LTspice immediate calculates the exact values even in a very complex/difficult circuits while manual calculation do not. Manual calculation would take time to calculate unknown especially if we expand the circuit into a difficult one. Mier:

VII.

Answer to Guide question

Is simulation important? Why? Or Why not? Lapuz: It is important to simulate such circuits especially to a very complex one, because it takes time to solve when using manual calculations. As a chemical engineering student, I have an insight that in industries, we are dealing with complex, broad, and difficult problems. In order to solve that, I rather use softwares rather than doing manual calculations to reduce percent errors and to have accurate values.

Ref Reference erence https://www.ndeed.org/EducationResources/CommunityCollege/EddyCurrents/Physics/currentflow.htm#:~:text= Ohm's%20law%20states%20that%20the,the%20circuit%20does%20not%20change.

https://www.physicsclassroom.com/class/circuits/Lesson-2/Electric-Current#:~:text=The %20direction%20of%20an%20electric%20current%20is%20by%20convention%20the,wires %20in%20the%20opposite%20direction.

http://www.doe.carleton.ca/~nagui/Web2501/PSpicePrimer.pdf...