MODULE TITLE : PROGRAMMABLE LOGIC CONTROLLERS TOPIC TITLES : INTRODUCTORY BASIC THEORY, DEVELOPMENT OF PLCs AND INTERFACING TUTOR MARKED ASSIGNMENT 1 NAME........................................................................................................................................ ADDRESS ................................................................................................................................. ................................................................................................................................................... ................................................................................................................................................... ...................................................... HOME TELEPHONE ..................................................... EMPLOYER.............................................................................................................................. ................................................................................................................................................... ................................................................................................................................................... ...................................................... WORK TELEPHONE...................................................... PLC - 1 - TMA (v1) © Teesside University 2011 THIS BOX MUST BE COMPLETED Student Code No. .................................................................................................... Student's Signature .................................................................................................. Date Submitted ........................................................................................................ Contact e-mail .........................................................................................................Published by Teesside University Open Learning (Engineering) School of Science & Engineering Teesside University Tees Valley, UK TS1 3BA +44 (0)1642 342740 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without the prior permission of the Copyright owner. This book is sold subject to the condition that it shall not, by way of trade or otherwise, be lent, re-sold, hired out or otherwise circulated without the publisher's prior consent in any form of binding or cover other than that in which it is published and without a similar condition including this condition being imposed on the subsequent purchaser.IMPORTANT Before you start please read the following instructions carefully. 1. This assignment forms part of the formal assessment for this module. If you fail to reach the required standard for the assignment then you will be allowed to resubmit but a resubmission will only be eligible for a Pass grade, not a Merit or Distinction. You should therefore not submit the assignment until you are reasonably sure that you have completed it successfully. Seek your tutor's advice if unsure. 2. Ensure that you indicate the number of the question you are answering. 3. Make a copy of your answers before submitting the assignment. 4. Complete all details on the front page of this TMA and return it with the completed assignment including supporting calculations where appropriate. The preferred submission is via your TUOL(E) Blackboard account: https://eat.tees.ac.uk 5. Your tutor's comments on the assignment will be posted on Blackboard. 1 Teesside University Open Learning (Engineering) © Teesside University 20111. (a) By using a truth table show that the expressions are equivalent. (b) Show by plotting truth tables that NAND gate NOR gate inverter 2. (a) Draw the logic circuit to represent the following Boolean expression using only NAND gates. (b) Draw the logic circuit to represent the following Boolean expression using only NOR gates. Indicate the outputs of each gate. F A B A B = + + + F AB BC AC = . . ≡ ≡ ABC AC BC ABC + + = 2 Teesside University Open Learning (Engineering) © Teesside University 20113. In the ladder diagram shown in FIGURE 1, Y006 is a lamp, X and R references are relay contacts. Write down the Boolean expression for the lamp to light. FIG. 1 4. (a) Add the following HEX numbers converting to binary. Express the answer in HEX. (i) 08 + 03 (ii) 0ABC + DA0E. (b) Write down the 2's complement of: (i) 00000001 (ii) 00111100 (c) Convert the following denary numbers to 8 bit binary numbers and evaluate using the '2's' complement' method. Leave your answers in binary form. (i) 17 – 8 (ii) 97 – 125 (d) (i) Write down the bcd form of decimal 845. (ii) Convert the denary number 818 first to hexadecimal then to binary. Show all working. X001 X005 R001 Y006 X002 X003 R000 3 Teesside University Open Learning (Engineering) © Teesside University 20115. State three disadvantages of relays when compared with the use of PLCs in process control circuits. 6. (a) State what is meant by input and output interfaces in relation to PLCs. (b) State briefly what the function of interfaces is in relation to the different types of process signal. (c) The diagram of FIGURE 2 shows a bi-directional opto coupler input interface circuit. When a supply voltage of 20 V is applied the LED carries a current and 2 V is dropped across it. Calculate the value of the LED current and the value of current through the 3 kΩ resistance. FIG. 2 3kΩ 470Ω Signal to microcomputer Bi-directional opto-coupler External wiring Internal wiring Separate supply used for inputs. Note: Either polarity. Switch 4 Teesside University Open Learning (Engineering) © Teesside University 2011(d) The circuit shown in FIGURE 3 is part of the interface of a relay output module. Ib is 1 mA and VCC is 9 V. The relay requires a minimum of 50 mA to energise. Complete the values of the assumptions listed below in order to calculate: • voltage across R1 • value of R 1 • voltage across the relay coil • voltage across R2 • value of R 2 • collector of current I c. Assumptions: Logic '1' = V Logic '0' = V Transistor forward current gain hfe = LED current = 10 mA LED voltage drop at 10 mA = V Base/emitter voltage = V Collector emitter voltage when transistor is on = 1 V 5 Teesside University Open Learning (Engineering) © Teesside University 2011FIG. 3 R R 1 R 2 +V CC N/O External Terminals Logic Signal 0 volts 6 Teesside University Open Learning (Engineering) © Teesside University 2011Teesside University Open Learning (Engineering) © Teesside University 2011 Question No.Teesside University Open Learning (Engineering) © Teesside University 2011 Question No.Teesside University Open Learning (Engineering) © Teesside University 2011 Question No.