Download Unit 8: Electronic Circuit Design and Construction

Assignment
title
DC Networks
Assessor
Paul Lewis
Date issued
Final deadline
Duration
(approx)
2 sessions (8 hours)
Qualification
suite covered
BTEC Extended Diploma in Engineering Level 3
Units covered
A part of Unit 6 Electrical and Electronic Principles
Learning aims
covered
Be able to use circuit theory to determine the current, voltage and resistance in
direct current (DC) circuits
Scenario
You have been employed as a junior technician in a local electronics company
who make power supplies. A new power supply has appeared on the market
which used considerably less power that the one made by your company. You
have been commisioned by your managing director to investigate the power
drawn by your power supply circuits and suggest possible alternatives
Task 1
Part a)
For the circuit shown below:
Choose 5 different value resistors from the following table for resistors R1 – R5
Calculate the total power dissipation of your circuit then choose a suitable
voltage from the table below based on this value
Resistor values for R1 –
Voltage values for V1
R5
10 Ω
3 volts
22 Ω
5 volts
33 Ω
6 volts
47 Ω
9 volts
100 Ω
10 volts
220 Ω
12 volts
330 Ω
15 volts
470 Ω
24 volts
1k Ω
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Calculate:
The total circuit resistance Rt
The total circuit current It
The current flowing through R3
The voltage dropped across R2
The power dissipated by R1
Confirm the results of your calculation using the laboratory simulator
(Multisim)
Care should be taken by each student to ensure that where possible, the combination of
components and supply voltage are unique for each assessment.
Part b)
Check your calculations for P1 by constructing the circuit on breadboard and carefully
measuring the values of resistance, current and voltage as specified. Make a table similar
to the one shown below and enter your values.
Parameter
Calculated
values
Measured
values
Simulated values
Total circuit
resistance
Total circuit
current
Current flowing
through R3
Voltage dropped
across R2
Power dissipated in
R1
Part c)
Use DC circuit measurements to calculate the internal resistance of a battery
Measure the offload voltage of a given battery using a multimeter
Measure the onload voltage of the battery when connected to the virtual cat
circuit using a multimeter
Measure the current drawn by the virtual cat circuit using a multimeter
Use the data from the measurements to calculate the internal resistance of the
battery
Include all of the above data in a technical report
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Part d)
You are required to use test equipment to measure the forward and reverse
characteristics of two semi-conductor diodes. You should use a 1N4001 diode
and a zener diode to carry out this experiment.
Use the following circuit as a basis for this test:
Draw and label a diagram of the 1N4001 general purpose diode
connected in forward bias and reverse bias mode
Measure the forward characteristic of the diode between 0.5 volts and
0.7 volts using steps of 0.01 of a volt by adjusting the resistance box R1
Measure and record the reverse characteristic of the diode using
Multisim between 49.9 volts and 50.01 volts using steps of 0.01 of a volt
Carry out a similar experiment on a zener diode (of your choice) using
its data sheet as a guide to the magnitude of voltages required to test
its forward and reverse characteristics
Draw and label graphs of both data sets
Compare the two graphs showing the conduction characteristics of both
diodes, consult the data sheets and evaluate your findings in terms of
forward and reverse voltages, power dissipation and maximum operating
current
Evidence you
must produce
for this task
Formulae, calculations and solutions neatly presented
Photographic evidence showing the DC Network for both resistors,
diodes and the internal resistance of a battery.
Photographic evidence of all readings taken by the multimeter
Readings taken for the forward and reverse current and voltages
through and across both diodes to be neatly tabulated
Graphs to be drawn to show the conduction characteristic of both
diodes in both forward and reverse bias modes
Your evidence should be presented in the form of a report which
contains and introduction to each task and a written conclusion
Criteria covered by Task 1:
Unit
Criterion
reference
Use DC circuit theory to calculate current, voltage and resistance in
DC Networks
Use a multi-meter to carry out circuit measurements in a DC circuit
6
P1
6
P2
Compare the forward and reverse characteristics of two different
semi-conductor diodes
6
P3
To achieve the criteria you must show that you are able to:
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Task 2
For the circuit shown below:
Use the same table as for Unit 6 P1 in order to choose component values.
Circuit 2
From the attached table choose different values for R1 – R3
From the attached table choose different voltages for V1 –V2
Use Kirchoff’s laws to determine the current flowing through R1, R2 and
R3
Determine the power dissipation in R1
Use Multisim to confirm the results of your calculations and attach to the
assignment as a screen dump
Evidence you
must produce
for this task
Formulae, calculations and solutions neatly presented
A screen dump from a simulation showing the current through R1 and the
voltage across R1.
Criteria covered by Task 2:
To achieve the criteria you must show that you are able to:
Use Kirchoff’s laws to determine the current in various parts of a
network having four nodes and the power dissipated in a load
resistor containing two voltages sources
Task 3
Unit
Criterion
reference
6
M1
The circuit shown below is a simple voltage regulated power supply:
Investigate the function and operation of the circuit and choose components to produce
an output voltage with the following specification:
 Output voltage = 5 volts
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
Output current up to a maximum of 100 mA

Ripple voltage <10mV
The values can have a tolerance of +/- 5%
 Simulate the circuit to prove its operation
Evidence you
must produce
for this task

Explain how and why the value for each component was chosen

Build and test the final solution and evaluate its performance against the given
specification
Formulae, calculations and solutions neatly presented
Photographic or video evidence of the circuit with readings showing that the
circuit is performing to specification
A simulation proving that the components chosen allow the circuit to
perform within the specified parameters
Criteria covered by Task 2:
To achieve the criteria you must show that you are able to:
Analyse the operation and the effects of varying component
parameters of a power supply circuit that includes a transformer,
diodes and capacitors
Unit
Criterion
reference
6
D1
Sources of
information
Websites
http://www.bassix.eu
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