LAB 6: Introduction to Proteus Simulation Software
Objective:
To learn the Proteus Simulation Software and use it to measure electrical quantities.
Learning Outcome:
The ability to use Proteus Simulation Software to simulate electric circuits and measure electrical quantities.
Equipment:
Proteus Simulation Software
Task 1: Installing the Proteus Simulation Software
The Proteus Simulation Software is available in the CAD Lab, Faculty of Engineering. The demonstration version can be downloaded via https://www.labcenter.com/downloads/. You can use the demonstration version if you cannot come to the CAD Lab.
Task 2: Measuring resistance, voltage, and current
2.1 Construct the series-parallel circuit in Figure 6.1. Use R1 = 330?, R2 = R3 = 1k?.
Figure 6.1
2.2 Use an ohmmeter to measure the equivalent resistance, Req. Record the measured value.
2.3 Explain why resistance shouldn’t be measured in a live circuit?
2.3 Connect a dc voltage supply with Vs = 10V across points A and B. Measure the voltage across each resistor using a dc voltmeter. Does your observation agree with the Kirchhoff Voltage Law?
2.4 Measure the current that flows through each resistor using a dc ammeter. Does your observation agree with the Kirchhoff Current Law?
Task 3: Using a signal generator
3.1 Construct the series RLC circuit in Figure 6.2. Use R=400 ?, C=0.01µF, and L = 50 mH.
Figure 6.2
3.2 Calculate the resonant frequency, f0 (not the angular frequency, ?o), in Hz by using the following formula:
(3)
Calculation:
3.3 Set the signal generator frequency, f near the value calculated with a voltage amplitude of about 5 Volts, sinusoidal.
3.4 With the RLC circuit set up, measure the voltage, V across the resistor. Now vary the frequency f to find the maximum voltage (it will likely not be the full 5V). This frequency will probably be a little different from your calculation.
3.5 Take many (at least four on each side of fo) measurements of V in the vicinity of the resonant frequency, ensuring that you tune the signal generator through a broad range of frequencies, so you see the voltage drop off by at least one-third on each side of the peak voltage. Record your data in Table 6.1.
3.6 Now change R to 200 ? and repeat the measurements. Record your data in Table 6.1.
3.7 Now change R to 100 ? and repeat the measurements. Record your data in Table 6.1.
L:______________ C:_____________ f0:_______________
Table 6.1
R = 400 ? R = 200 ? R =100 ?
Frequency (Hz) Voltage
(V) Voltage
(V) Voltage
(V) Frequency (Hz) Voltage
(V)
f0 f0 f0
3.8 Plot Voltage vs. Frequency (y vs. x) for all three data sets on a single grid, plotting the data for R = 400 ? first as it should be broadest. Use three different markers: solid circles for 400 ?, hollow squares for 200 ?, and small x’s for 100 ?. Connect each different data set with a smooth line forming a bell-shaped curve.
3.9 How do the resonant frequencies compare in the three plots? Is this expected? Explain.
Task 4: Observe and measure waveforms using an oscilloscope
4.1 Construct the RC circuit in Figure 6.3. Use a variable resistor of 100k? and C=0.001µF. Set the signal generator to square wave signal, 5000Hz, 8Vpp. Connect channel A of the oscilloscope to the signal generator and channel B to the capacitor.
Figure 6.3
4.2 Adjust the VOLT/DIV and SEC/DIV knobs to enlarge the signals. Does channel A display the same signal as supplied by the signal generator? What are the amplitude and frequency?
4.3 Adjust the resistance of the variable resistor to 10k?. Observe the signals displayed by channels A and B. Screenshot the waveforms and paste them below.
4.4 Explain why the voltage across the capacitor is behaving like that.
4.5 Suggest one system that may use the RC circuit. Explain the function of the RC circuit in the system.
Task 5: Mystery Circuit
5.1 Construct the circuit in Figure 6.4.
Figure 6.4
5.2 Observe and record what the circuit produces at the Out1, Out2, and Out3 pins.
5.3 Vary the potentiometer resistance, observe Out1, Out2, and Out3. Based on your observation, can you name the circuit?
LAB 7: The Thévenin Equivalent Circuit
Objective:
To characterize multiple resistive networks by its Thévenin’s equivalent circuit.
Learning Outcome:
Ability to obtain and analyze the Thevenin equivalent circuit.
Instrument/Component:
Proteus Simulation Software
Theory:
Thévenin’s Theorem: It is a process by which a complex circuit is reduced to an equivalent series circuit consisting of a single voltage source (VTH), a series resistance (RTH) and a load resistance (RL). After creating the Thévenin Equivalent Circuit, the load voltage VL or the load current IL may be easily determined.
One of the main uses of Thévenin’s theorem is the replacement of a large part of a circuit, often a complicated and uninteresting part, by a very simple equivalent. The new simpler circuit enables us to make rapid calculations of the voltage, current, and power that the original circuit is able to deliver to a load. It also helps us to choose the best value of this load resistance for maximum power transfer.
Figure 7.1
Figure 7.2 Thevenin equivalent circuit of Figure 7.1
Maximum Power Transfer Theorem states that an independent voltage source in series with a resistance RS or an independent current source in parallel with a resistance RS, delivers a maximum power to that load resistance RL for which RL = RS.
In terms of a Thévenin Equivalent Circuit, maximum power is delivered to the load resistance RL when RL is equal to the Thévenin equivalent resistance RTH of the circuit.
Figure 7.3 Maximum Power Transfer
Task 1: Verifying Thévenin’s theorem
1.1 Construct the circuit of Figure 7.1 using the following component values:
R1 = 300 ?
R2 = 560 ?
R3 = 560 ?
R4 = 300 ?
R5 = 820 ?
RL = 1.2 k?
VS = 10 V
1.2 Measure the voltage VL across the load resistance, RL.
1.3 Find VTH: Remove the load resistance RL and measure the open-circuit voltage, Voc across the terminals. This is equal to VTH.
1.4 Find RTH: Remove the source voltage VS and replace it with a short circuit. Measure the resistance by looking into the opening where RL was with an ohmmeter. This gives RTH.
1.5 Obtaining VTH and RTH, construct the circuit of Figure 6.2. Set the value of RTH using a variable resistor. For simulation using Proteus just use the ordinary resistor and change the value to the RTH value. Measure the VL for this circuit and compare it to the VL obtained from the circuit of Figure 7.1. State your observation.
1.6 Construct the circuit as in Figure 7.3 using the following values:
VS = 10 V
R1 = R2 = 560 ?
R3 = 820 ?
RL = Variable Resistor (0-2k?)
1.7 Connect the Voltmeter across RL for measuring the load voltage (VL) and Ammeter through RL for measuring load current (IL). Vary the resistance between 600 ??to 1.6 k??and note down VL and IL for each case. Calculate the power delivered to the load, PL. Record the results in Table 7.1.
Table 7.1
RL (ohm) IL (mA) VL (V) PL (mW)
600
900
1000
1100
1200
1400
1600
1.8 The value of RL at which PL is maximum, gives the load resistance for maximum power transfer. Calculate the RTH for the circuit in step 1.7 and discuss your finding.
Task 2: Thevenin Theorem
PreLab:
2.1 The circuit in Figure 7.4 (a) can be converted to (b) using the Thevenin theorem.
(a) (b)
Figure 7.4
2.2 Calculate VTH and RTH given that R1 = 50 ?, R2 = 2.2 k?, R3 = 4.7 k? and Vin = 5V.
2.3 Construct the circuit shown in Figure 7.4(a). Use 50k? Variable Resistor for RL.
2.4 Record and plot IO versus the voltage at node VO relative to the ground for six different values of RL.
Table 7.2
RL (ohm) VO (V) IO (mA)
5k
10k
20k
30k
40k
Open-circuited (8)
2.5 From the plot, derive an equation relating IO and VO. From the equation, infer and obtain the Thévenin parameters (VTH and RTH).
2.6 Compare the measured values with the calculated values from the prelab. Explain the differences between the values, if any.
2.7 Construct the circuit in Figure 7.4(b) using the obtained VTH and RTH values in step (2.5). Measure IO and VO for this network using the same load resistors as in step (2.4).
Table 7.3
RL (ohm) VO (V) IO (mA)
5k
10k
20k
30k
40k
Open-circuited (8)
2.8 What is the significance of step (2.7)? What does this experiment tell you about the concept of equivalence?
Task 3: Investigation
Now you can determine the Thévenin equivalent circuit of a battery. Be sure not to short circuit the battery.
State the procedures required to obtain the parameters of the Thévenin equivalent circuit for the battery.
