MODULE TITLE : PROGRAMMABLE LOGIC CONTROLLERS TOPIC TITLE : LADDER DIAGRAM PROGRAMMING AND STRUCTURE OF THE PLC TUTOR MARKED ASSIGNMENT 2

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Beverly Maxwell
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1 THIS BOX MUST BE COMPLETED Student Code No.... Student's Signature... Date Submitted... Contact ... MODULE TITLE : PROGRAMMABLE LOGIC CONTROLLERS TOPIC TITLE : LADDER DIAGRAM PROGRAMMING AND STRUCTURE OF THE PLC TUTOR MARKED ASSIGNMENT 2 NAME... ADDRESS HOME TELEPHONE... EMPLOYER WORK TELEPHONE... PLC TMA (v1.1) Teesside University 2011

2 Published by Teesside University Open Learning School of Science & Engineering Teesside University Tees Valley, UK TS1 3BA +44 (0) 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. Teesside University 2011

3 1 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: 5. Your tutor s comments on the assignment will be posted on Blackboard.

4 2 1. The circuit diagram of FIGURE 1 is of a bell indicator circuit. SW1 P2 P1 R3/2 IND 3 R2 R1/2 IND 1 BELL R1/1 P3 R2/2 R1 R3 IND 2 R2/1 R3/1 FIG. 1 (a) Convert this diagram into industrial ladder diagram format (retain all devices). (b) (i) Convert the diagram of FIGURE 1 into a suitable PLC ladder diagram having the simplest form. (ii) Provide I/O designation charts to show your choice of inputs and outputs. (iii) State three benefits obtained by the PLC implementation.

(ii) Identify all inputs and outputs by the use of I/O designation charts.

5 3 2. The diagram of FIGURE 2 is an extract from an industrial control panel wiring diagram. FIG. 2 (i) Convert the diagram into PLC format. (ii) Identify all inputs and outputs by the use of I/O designation charts. (iii) With respect to the operation of the circuit: (a) explain the purpose of rung 1

6 4 (b) explain fully the condition of the circuit elements when indicator IND2 is illuminated (c) If indicator IND3 is on, explain what will happen if P3 is operated. 3. Provide a block diagram of a PLC system which contains the following: (i) (a) a CPU (b) a system clock (c) a power supply (d) input and output interfaces (e) a keyboard (f) a display device (g) necessary types of memory. Describe very briefly the function and essential features of each block. (ii) Use the diagram shown in FIGURE 3 to briefly explain the fetch/execute cycle of a microprocessor for the instruction BC. The instruction is stored in memory locations 1661 to The op code means 'store the contents of the accumulator in memory address location'. The address given is in the reverse order. The contents of the accumulator are 78H. Indicate the contents of the PC, AS, registers, accumulator and address BC00 after the cycle is completed.

7 5 FIG. 3

8 6 4. The circuit of FIGURE 4 shows a 3-phase, star/delta motor starting circuit. The motor is initially connected in star (contactors C 1 and C 3 close to form a star with the three motor windings) and run up to speed, then the circuit is switched to run in delta (i.e. a triangular connection of the windings) for normal running (contactor C 3 opens and C 2 closes, contactor C 1 remaining closed). FIGURE 5 shows the control circuit for the motor. The 3 amp fuse can be regarded as a normally closed switch (N/C), and a contact from the fused isolator as a normally open (N/O) switch. The overload current (O/L) can be regarded as a N/C switch and the start button as a N/O switch. The CENT N/C contacts are operated by a centrifugal switch on the motor and open when the motor has reached a run-up speed connected in star. The contact positions in FIGURE 5 are the positions of the de-energised control circuit (prior to the start button being pressed). (a) Describe briefly how you think the motor control circuit of FIGURE 5 sequence of events proceeds after pressing the start button. (The start button returns to the open position on release.) (b) Convert the circuit to a ladder diagram using conventional plc designations for ladder input components (X000, X001, etc.) for switches, contacts, etc. and output designations Y001, Y002, Y003 for output contactor coils C 1, C 2, C 3. Output contactor contacts in the control circuit should be designated as Y001 (1 1), Y002 (2 1), Y003 (3 1) and Y003 (3 2). Input and output designation tables may be drawn up or, alternatively, FIGURE 5 component designations can be indicated alongside the chosen plc designations. Memory relays may be used if desired. 5. Explain the operating features of an I/O data image table.

9 7 FIG. 4

10 8 FIG. 5

11 Question No.

Chapter 2 Programmable Logic Controller (PLC) and Relay Ladder Logic (RLL).

Controller PLC and Relay LAdder Logic RLL -IE337 Chapter 2 Programmable Logic Controller (PLC) and Relay Ladder Logic (RLL). 1 Controller PLC and Relay LAdder Logic RLL -IE337 2.1 PLC Operation using scanning