# design various electrical systems

design various electrical systems

Introduction

You are required to analyse and design various electrical systems in a modern automobile using

knowledge and skills gained in the EAT113 module. You will consider:

1. Replacement of vehicle lamps with low power LEDs.

2. Digital logic design and simplification of an Electronic Control Unit (ECU) function.

3. Design of a capacitor-based regenerative braking energy recovery system.

Each section is worth equal marks.

Instructions

In order to carry out each exercise you will need to use personalised values based on your student ID

number, which should be clearly stated. Your answer to each question should include the full

method used to calculate your results. Be sure to clearly explain what you have done and how you

have done it at each stage.

Zero marks will be awarded if:

? No explanation of the calculations is presented, or your results are unclear.

? You fail to use the correct values for the calculations based on your student ID.

There is no requirement for you to perform any background research for this exercise, and no marks

will be awarded for research.

Your report should be submitted to the Assignment Desk in St Peter’s Library, Prospect Building, in

person or by post, by 4pm on Friday 21st August 2015.

Electronic Submission is not accepted for this assignment and work which is submitted late or via an

incorrect mode of submission will not be marked.

Any questions regarding this assignment should be addressed to walter.ditch@sunderland.ac.uk

Part 1 – Vehicle Lights

The vehicles light system consists of the following bulbs:

Lamp Number Wattage

Headlamp 2 45 W

Running Lamp 2 30 W

Indicator 2 20 W

Fog Lamp 2 30 W

Number Plate Lamp 2 5 W

Brake Lamp 3 20 W

Reversing Lamp 1 20 W

Rear Lamp 2 10 W

These lamps are to be replaced by a special type of Light Emitting Diode (LED). Three of these LEDs

connected in series are capable of producing the same light output as a 5W bulb. You may assume

that the light output of a higher wattage bulb can be obtained by connecting additional parallel LED

banks, e.g. 10 W Conventional bulb can be replaced by 6 LEDs, 15 W conventional bulb can be

replaced by 9 LEDs etc. As an example, replacement LED circuits for 5 W and 10 W lamps are shown

below.

The maximum LED current is given by 1XX mA where XX is the last two digits of your student

number, e.g. if your student number is 123654876, the maximum current the LEDs can operate at is

176 mA. When fully activated you should assume the LED forward voltage is 3 V. The vehicle power

supply system is 12 V. When the engine is not running a 40 Ah battery is used to supply the lights.

This means that the battery can supply 40 A for one hour, 20 A for two hours, 1 A for 40 hours, etc.

Task 1A

The LEDs are to be wired in series combinations of three LEDs with a protection resistor in place to

limit the current. Calculate the value of this protection resistor and explain your calculation.

(5 marks)

Task 1B

Calculate the power used in each LED circuit. Determine the percentage reduction in power when all

lights are activated compared to the original bulbs.

(5 marks)

Task 1C

Determine the increase in the time the lights can be powered (assuming all lamps are illuminated)

before the battery becomes discharged.

(5 marks)

Task 1D

Make a recommendation for the current rating of a fuse for the Headlamps (only). Be sure to explain

any calculations you have used and justify your answer.

(5 marks)

(Total for Task 1: 20 marks)

Part 2 – Digital Logic Design.

Operation of an important part of the Electronic Control Unit (ECU) is a combinational logic function

based on four sensors: A, B, C, and D. The output (Y) of the function is based on the following truth

table, which is to be customised based on your student number.

Row A B C D Y (Output)

0 0 0 0 0 ?

1 0 0 0 1 ?

2 0 0 1 0 ?

3 0 0 1 1 ?

4 0 1 0 0 ?

5 0 1 0 1 ?

6 0 1 1 0 ?

7 0 1 1 1 ?

8 1 0 0 0 ?

9 1 0 0 1 ?

10 1 0 1 0 1

11 1 0 1 1 1

12 1 1 0 0 1

13 1 1 0 1 1

14 1 1 1 0 1

15 1 1 1 1 1

To complete the truth table above, you should identify each unique digit in your student number

and write a ‘1’ in the equivalent output row above, and ‘0’ otherwise. For example, if your student

number is 111224467, you would write a 1 in the output of rows 1, 2, 4, 6 and 7, and write a ‘0’ in

the output of rows 0, 3, 5, 8 and 9.

Task 2A

Create a Karnaugh map based on your truth table and identify the simplified Boolean expression of

your circuit.

(10 marks)

Task 2B

Draw a logic circuit based on your simplified Boolean expression.

(10 marks)

(Total for Task 2: 20 marks)

Part 3 – Regenerative Braking

A regenerative braking system is installed in the vehicle. This will use supercapacitors to store the

energy recovered during deceleration, using this energy later to assist the acceleration of the

vehicle. The mass of your vehicle is 1,XX0 kg where XX are the last two numbers of your student

number.

Part 3A

Calculate the maximum amount of energy which can be harvested when a vehicle slows from 40

km/hr to a standstill.

(5 marks)

Part 3B

A parallel bank of 100 supercapacitors is to be used to store the energy. Each supercapacitor has a

capacitance of 1.5 F. Assuming that all of the available energy is captured, determine the voltage to

which the capacitors must be charged to store the captured energy.

(5 marks)

Part 3C

Determine the total charge which is transferred to the capacitor bank under braking.

(5 marks)

Part 3D

Caclulate the average current which must flow if it takes 10 s for the vehicle to slow down.

(5 marks)

(Total for Task 3: 20 marks)

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