elec3117-2010 exam paper

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Name: _______________________

Student ID: ___________________

Signature: ____________________

THE UNIVERSITY OF NEW SOUTH WALES

School of Electrical Engineering & Telecommunications

FINAL EXAMINATION

Session 2 2010

ELEC3117Electr ical Engineering Design

TIME ALLOWED: 3 hoursTOTAL MARKS: 100TOTAL NUMBER OF QUESTIONS: 4

THIS EXAM CONTRIBUTES 40% TO THE TOTAL COURSE ASSESSMENT.

Reading Time: 10 minutes.

This paper contains 6 pages .

Candidates must ATTEMPT ALL questions.

Answer each question in a separate answer book.

Marks for each question are indicated beside the question.

This paper MAY be retained by the candidate.

Print your name, student ID and question number on the front page of each answer book.

Authorised examination materials:

Drawing instruments may be brought into the examination room.

Candidates should use their own UNSW-approved electronic calculators.

This is a closed book examination.

Assumptions made in answering the questions should be stated explicitly.

All answers must be written in ink. Except where they are expressly required, pencils mayonly be used for drawing, sketching or graphical work.

ELEC/TELE/PHTN 3117

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QUESTION 1 [26 marks ]

A. [6 marks] Briefly describe four (4) methods for discovering customers needs for apotential new electronic product, elaborating on their advantages and disadvantages.Explain how you would use one of these methods to identify the usabilityrequirements for the new product.

B. [4 marks] Explain what is meant by window of opportunity, listing the factors thatcontribute to the window of opportunity.

C. [8 marks] You are the project manager for a product that was estimated to cost $3million to develop and to give a net present value (NPV) profit of $1 million. The

project is halfway through and although you are keeping to the original timeline, $3.5million have already been spent. Revised estimates indicate that the product will becompleted on time but will require an additional $2.5 million in funds. One of yourengineers proposes a modification to the plan that will allow the product to becompleted with an additional investment of only $2.2 million and will give a total

NPV profit of $1.2 million, calculated based on the costs and revenue from this pointforward (that is the recalculation eliminates all past considerations of costs andrevenues.)All other things being equal, and assuming there is has been no discount in the valueof the dollar between the original estimate and the re-evaluation, determine whether

the project should be abandoned, should continue as is, or the plans should change assuggested by the engineer. You must justify your answer.

D. [8 marks] Discuss and explain the various steps and activities involved in the designof a new product, starting from the identification of a product concept through to thehigh level design.

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A. [2 marks] Explain what is meant by the term lead userand how they might contributeto process of product development.

B. In the context of project management(i) [4 marks] Explain the function of a project plan and comment on the

importance of sticking to it.(ii)[4 marks] What activities, in addition to planning, are important?

C. [6 marks] Explain the difference between regulatory and industry standards, referringto the role they play in new product development. List three (3) reasons for the needfor industry standards.

D. [4 marks] Discuss the purpose of the ISO9001 standard and its implications for the

design process.

E. [3 marks] List three (3) fundamentally different reasons that might prevent you frompatenting an invention.

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A. [6 marks](i) Discuss the interaction between cost, price, and sales volume in relation to

product pricing using graphs/equations where appropriate.(ii)Explain the two methods for setting the price of a product placing them in the

context of the interaction between the three factors in product pricingdiscussed in part (i).

B. [4 marks] Explain what is meant by Return on Investment (ROI) in the context ofproduct economics. In particular, how would you use the projected ROI to determinewhether or not to go ahead with a product development project?

C. [6 marks] An engineering firm purchases a new high-tech assembly machine, which iscapable of performing both component insertion and soldering, as required.Depreciation, maintenance and operation expenses for this machine come to $2

million per year. The machine uses a pipelining strategy so that components can beplaced on one board at the same time that the previous board is being soldered. Themachine is capable of placing 400 components per minute and soldering 5 boards perminute. The machine can be operated for 8 hours a day, 5 days a week, for 48 weekseach year, allowing 4 weeks for maintenance.

(i) Identify (including values) the two cost drivers for this machine, explaininghow they should be used to assign the costs of operating the machine to the

products being manufactured.(ii)Using your answer to part (i), calculate the incremental soldering and insertion

charge associated with enlarging a circuit board, which already carries 60

components, to carry an additional 40 components.

D. [6 marks] Explain the difference between direct and indirect costs giving twoexamples for each category. Give a method for accounting for indirect costs in the

product development plan.

E. [4 marks] Explain why risk assessment is important in the context of the managementof a complex project.

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A. [8 marks] Consider the circuit design shown in the figure below.

(i) You are to assume that Vs = 10V, the control voltage Vc is a square wave ofsome frequency fc, and the resistor and inductor values are 50 and 5mHrespectively. Given the absolute maximum ratings data on the two transistors,taken from a datasheet, and shown in the table below which transistor, if any,would you choose for the circuit? You must justify your answer.

(ii)A colleague points out to you that the circuit has a problem. Explain what theproblem is and describe a possible solution to it.

B. [3 marks] For each of the following applications, identify the most appropriatecapacitor technology out of the following list: polyester film capacitors (green/redcaps); aluminium electrolytic capacitors; ceramic capacitors. In each case, explainyour selection.

(i) Bypass capacitor for an FPGA operating at 500 MHz.(ii)Smoothing capacitor for the rectified output from a 50Hz mains power

transformer in a 10W 5V power supply.(iii)Opamp-based low-pass filter for removing frequencies below 100 Hz from an

analog waveform.

C. [8 marks] Consider the integrator circuit depicted in the figure below. We want to use

this circuit to accurately integrate the input voltage waveform Vin(t) for a period of 10seconds! The integral might be positive or negative. The maximum output swing onthe opamp is +/- 5V and Vin(t) lies in the range -1V to +1V.

(i)Noting that the I-V relationship for a capacitor is I = C dV/dt, what would be agood choice for the time constant CR ?

Vs Vc

RVout

C

dump

VinR

VoutC

dump

Vin

Transistor 1 Transistor 2

Collector Emitter Voltage 80V 50V

Collector Current 100mA 1.5A

Peak Collector Current 200mA 3A

Total Power Dissipation 500mW 1.25W

Max. Operating Junction Temp. 150C 150C

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(ii)What capacitor types would be most appropriate for this type of application?Your answer should mention the types of capacitor you would not use andwhy.

(iii)Given your answers to parts (a) and (b) above, what would be good choicesfor the values of R and C? You should endeavour to use preferred values for

both R and C. You should also explain your reasoning.

(iv)What non-ideal property of the opamp would we be most concerned about forthis application? In view of this, what type of opamp would you select?(technology, not part number).

D. [6 marks] Describe at least 3 (three) PCB layout conventions which help either toreduce generated electromagnetic interference or increase immunity toelectromagnetic interference from other sources. In each case, explain why theconvention helps.

END OF EXAMINATION PAPER

elec3117-2010 exam paper

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