CE111 User Guide 0309
Short Description
2...
Description
CE111 PLC Process
User Guide
© TecQuipment Ltd 2009 Do not reproduce or transmit this document in any form or by any means, electronic or mechanical, including photocopy, recording or any information storage and retrieval system without the express permission of TecQuipment Limited. Limited . TecQuipment has taken care to make the contents of this manual accurate and up to date. However, if you find any errors, please let us know so we can rectify the problem. TecQuipment supplies a Packing Contents List (PCL) with wit h the equipment. Carefully check the contents of the package(s) against the list. If any items are missing or damaged, contact TecQuipment or the local agent.
PW/DB/bs/0309
Contents Section 1.0
2.0
Page INTRODUCTION
1
1.1 1.2 1. 2 1.3 1. 3
1 2 4
EXPERIMENTS 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8
3.0
General CE1 CE 111 PL PLC C Pr Pro oce cess ss CE12 123 3 PL PLC C Train iner er
Introduction Initial Setup Conn Co nnect ectio ion n of In Input puts s an and d Ou Outp tput uts s Exper Ex perim iment ent 1: Bas Basic ic Pr Progr ogram ammin ming g Exe Exerc rcise ise Exper Ex perime iment nt 2: Bas Basic ic Lev Level el Co Contr ntrol ol (T (Tank ank 1) Experim Expe riment ent 3: Leve Levell Cont Control rol (T (Tank ank 1 and Tank 2) Exper Ex perim iment ent 4: Tan ank k Fi Filli lling ng Seq Sequen uence ce Exper Ex perim iment ent 5: Sim Simul ulate ated d Bat Batch ch Seq Sequen uencin cing g
RESULTS
7
7 8 9 11 13 17 19 21
27
APPENDIX A: USEFUL TEXTBOOKS
29
APPENDIX B: BLANK EXPERIMENT PANELS
31
SECTION 1.0 Introduction
1.1
General
The CE111 PLC Process described in this manual is one of a range of TecQuipment bench-mounting modular units designed to practically investigate the basic and advanced principles of control engineering. Figure 1 shows a typical configuration consisting of the CE111 adjacent to the CE123 PLC Trainer and a PC. This configuration is capable of a wide range of programmable logic control investigations.
Figure 1 The CE111 Process and CE124 PLC Trainer The CE111 PLC Process can be operated by the CE123 PLC Trainer programmed from a PC (not supplied). The CE 111 PLC Process relates specifically to fluid transport, liquid level control and batch process control problems as they would typically occur in process control industries. The basic concept, however, of logic sequential control of industrial processes is quite general and the ideas demonstrated with the CE111 are equally applicable to other branches of industry. The CE111 provides an intrinsically safe, adaptable and self-contained facility for students of control engineering so that they may practically investigate and compare a wide range of functional control system configurations. In particular, with the CE111, they are able to examine the control of the level of liquid within a tank which can be set to drain or fill, using batch processing and logical sequence control.
IMPORTANT
The CE111 is supplied for connection to the CE123 PLC and takes its power from that apparatus. Do not connect the CE111 to other power sources.
The fundamentals of programmable logic controllers and their op eration are outlined in the CE123 manual. This section details the basic layout and panel features of the CE123. The experiment section gives a progressively complex
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experiment set designed to teach the basics of programmable logic control to utilising the more advanced features of the CE111 Process and the CE123 Trainer. The CE111 and associated documentation are devised to give the student an overall grounding in programmable logic control. The experiments provided with each of the apparatus in the Control Engineering range start with investigations into the characteristics of the transducer and drive circuits. As a circuit becomes more complex, with these circuits being interconnected, the student has less difficulty in understanding the combined, overall, performance. In the same way, it is recommended that the student spends some tim e investigating the functional abilities of the CE111 and CE123 s o that the use of programmable logic controllers and their abilities can be understood. This w ill enable the students to envisage other control applications and strategies as well as to appreciate the complex, combined, system more readily. To fully utilise the CE111 PLC Process and its faciltities, the student must first be familiar with the CE123 Programmable Logic Controller and its software.
1.2
CE111 PLC Process
Figure 2 The CE111 PLC Process The CE111 PLC Process, shown in Figure 2, is a bench-mounting modular instrument comprised of a reservoir pump and two tanks. The apparatus is equipped with solenoid operated valves to allow the filling and emptying of the tanks and also to allow the pump to discharge back to the reservoir. A manual pump speed control is provided to al low the user to vary the water flow rate through the pump. The equipment is complete with the drive circuitry necessary to operate the pumps and solenoid valves, as well as the necessary output devices. The two tanks have two level switches, the reservoir is also fitted with one float level switch to indicate sufficient liquid in the tank for correct operation. A rotary valve is also fitted to provide a pulsed output related to the flow rate of the liquid. Finally, an LED is attached adjacent to each front panel socket to indicate the status of the signal connected to it.
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The front panel layout of the CE111, shown in Figure 3, provides a logical and, hence, easy-to-use item of laboratory equipment co-ordinated with the rest of the TecQuipment Control Engineering range.
Figure 3 The CE111 Front Panel Each of the individual sections and elements are represented and accessed on the front panel in appropriately labelled functional blocks. The legends clearly detail the purposes of the circuits. The symbols used conform to international standards and also correspond to those used i n this manual.
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Table 1 shows the label, nature, and function of the front panel sockets. Socket Label
I/O
Function
L1
Output
Tank 2 LOW level Switch
L2
Output
Tank 2 HIGH level Switch
L3
Output
Tank 1 LOW level Switch
L4
Output
Tank 1 HIGH level Switch
L5
Output
Reservoir LOW level Float Switch
V1
Input
Pump to Reservoir Valve (by-pass)
V2
Input
Tank 1 Feed Valve
V3
Input
Tank 1 Drain Valve
V4
Input
Tank 2 Drain Valve
P1
Input
Pump ON/OFF
F1
Output
Flow meter, pulse related to flow r ate
Table 1 Details of the Front Panel Sockets Access to the input and output signals on the CE111 front panel is achieved utilising the appropriate 2 mm socket. (All sockets are internally protected against short-circuit and overload.) Filling the CE111 Reservoir and Priming the Pump
Before using the CE111 for the first time, it will be necessary to fill the reservoir with water and prime the pump. A coloured dye (supplied) may be added to the water before filling so the water levels can be seen more clearly. Add a f ew drops as necessary. Connect the 7-way umbilical lead into the rear of the CE123, and then make a patch lead connection between the Y4 output terminal on the CE123 and the V4 input terminal on the CE111. Switch on, press the Y4 ‘1’ override push-button on the CE123 in order to open the bottom tank drain valve. The reservoir can now be filled by pouring approximately five litres of water into the bottom tank and allowing it to drain into the reservoir. In order to prime the pump, the plastic pipe will need to be removed from the bottom of the one-way valve. Remove the four screws securing the CE111 front panel to gain access to this valve. Run the pump with this pipe disconnected until water flows from the pump output. This will allow water to fill the p ump unit. Replace the pipe and front panel.
1.3
CE123 PLC Trainer
The CE123 PLC Trainer, shown in Figure 4, is a bench-mounting modular instrument comprising of an industrial PLC, an input section, an output section, a serial port connector and a fuse holder and power supply switch. The front panel layout of the CE123, shown i n Figure 5, has been designed to provide a logical and, hence, easy-to-use item of laboratory equipment co-ordinated with the rest of th e TecQuipment Control Engineering range. Refer to the CE123 PLC Trainer manual for full details on its operation and use. The CE123 PLC Trainer manual also serves as an introduction to programmable logic control.
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Figure 4 The CE123 PLC Trainer
Figure 5 Front Panel of the CE123 PLC Trainer
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SECTION 2.0 Experiments
2.1
Introduction
The experiments described in this section are designed to provide practical support to the ladder diagram theory given in the CE123 PLC Trainer manual. All of these experiments, when used in conjunction with the theory, may be considered as a self-contained application of practical programmable logic control principles and applications. Additionally, once the basic principles have been investigated and understood, the equipment may be easily configured to illustrate a wider range of control topics. This may be necessary to comply with the experimental requirements of a particular syllabus. In each experiment it is assumed that the CE111 PLC Process is used in conjunction with the CE123 PLC Trainer . For any other combination it will be necessary to modify the instructions provided. It is recommended that the student works through the experiments associated with the CE123 before beginning this set of experiments. It is recommended that each student is supplied at the beginning of the experimental session with a photocopy, or similar, of the relevant experiment. Accordingly, TecQuipment gives its permission for any part of this manual to be copied provided that it is for internal college use only. On completion, the results, graphs and conclusions can then be compared and commented upon against the typical results provided at the end of this manual. The experimental connections between the CE111 and the CE123 follow a standard pattern so as to reduce setting up time, as well as simplify the presentation. This will not only increase the proportion of each laboratory period spent performing the experiments, but will also provide a better understanding of what is being achieved by each configuration. It is, however, important that care is taken to identify the correct terminals before a connection is made to achieve the required circuit and performance. It is recommended that the experiments are completed in the order given since the performances of the later assignments are to be compared with the earlier more basic experiments. The blank experimentation circuit diagrams provided in Appendix B are to allow users to develop their own test circuits. It is recommended that you photocopy the original outline drawings of the CE111/123 and then add the required connection leads. In this way the original may be used to produce an indefinite number of copies. The CE111 PLC Process/CE123 PLC Trainer combination provides a totally self-contained control system, with all devices and facilities required to assemble and investigate a wide range of control situations. In particular, the CE123 programming software provides all the features needed to monitor, document and observe the PLC sequences in action. No other equipment is required, apart from a printer for hard copy.
IMPORTANT
The performance of this equipment, as with any other scientific instrument, is dependent upon it being connected to a reliable and stable voltage mains supply. The Serial Number Plate, mounted at the rear of the unit, defines the corr ect power supply requirements.
Should the power supply vary during usage, for whatever reason, it must be anticipated that the performance of the equipment will be affected and the quality of the results impaired. In extreme cases, it may be necessary to consider the use of a voltage stabilising device. TecQuipment can accept no responsibility for damage caused to equipment which is connected to an unsuitable supply voltage.
NOTE
The experiments described here assume the user has a working knowledge of the CE123 PLC Trainer and the ladder logic programming method. This knowledge is obtained by performing the experiments in the CE123 manual. It is important therefore that students should work through the CE123 experiment sequence before attempting the experiments given here.
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Initial Setup
For all experiments, place the CE111 and the CE123 on a solid level bench. Allow enough space for a PC and a printer if required. Connect the lead from the CE111 to the CE123 as shown in Figure 6 and then proceed with the experiment.
WARNING
The CE111 uses water and the CE123 is connected t o a mains electrical supply. If water i s spilled anywhere on the apparatus, disconnect the electrical supply and clear up the spills. Do not reconnect the apparatus until an electrically qualified person has checked that it is safe. Always clear up any spills before connecting the mains supply. Disconnect the mains supply before adding water to or ‘top ping up’ the water in the CE111.
Figure 6 Connection Between the CE111 and CE123
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Connection of Inputs and Outputs
For all experiments, first make sure that the power to the CE123 is disconnected and then connect the CE111 to the CE123 with 2 mm leads as shown in Figure 7.
n o i t c n u F
Figure 7 Connection of Inp uts and Outputs Between the CE111 and CE123
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e t ) a r h s c s w t a i h o h h h p l c c t c w f c t t i i t i S y i o b w w t w w S t ( S S S t a d e t o t a t a l l e t a o a o F v a a l o l l o l l V l e e F F F l F l v i r r e e l e l e e o e e v l v v l e v e v l v l s v e v e l a a a e l l e l W r u l e V V V F F s O n i n O p H W H L e d i , r W e / a a G G e r R e r r N t O I O I i L H L H o t o F D D O e 2 2 1 1 v r p 1 1 2 p m k k k k e k k m k n n n n s n n n m w o a a a a e u a a a u l T T T T R P T T T P F
3 2 1 E C
1 2 3 4 5 1 2 3 4 0 0 X X X X X Y Y Y Y Y X
1 1 1 E C
1 2 3 4 5 1 2 3 4 1 1 L L L L L V V V V P F
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Experiment 1: Basic Programming Exercise
Object
The object of this experiment is to check the functionality of the CE111 and the CE123 PLC. The manual controls on the PLC are used to switch the CE111 inputs. Also the outputs of the CE111 are seen to operate on the CE123. Apparatus
CE111 PLC Process CE123 PLC Trainer. A PC and printer is not needed for this experiment. Procedure Part 1. Set Up
See “Initial Setup” on page 8. Part 2. Connect Inputs and Outputs
Connect the inputs and outputs between the CE111 to the CE123. See “Connection of Inputs and Outputs” on page 9. Part 3. Test the System
Turn on the power on the CE123 front panel. Use the manual selectors to set all outputs to Logic 0. The CE111 should now be inactive, except for the reservoir float switch and possibly the flow meter F1 output, which may or may not be illuminated. Ensure that the light L5 is ON and X5 is set HIGH (reservoir float switch). If not, top up fluid level. The valves are OPEN when they are set HIGH (logic 1) and CLOSED when set LOW (logic 0). Open and close each of the valves in turn and an audible click should be heard as they operate and the corresponding indicator light should operate. Set
Y1 ON – This opens the return to reservoir valve V1 Y0 ON – This starts pump P1
Set the pump speed control to maximum.
NOTE
Do not run the pump with both the bypass valve V1 and the feed valve to tank 1 (V2) closed. Close the valve V1 after valve V2 is opened, otherwise the fluid will flow through the bypass valve and not into tank 1.
The noise of the pump and the water going back into the reservoir tank should be audible. Open valves V2, V3, V4 (set CE123 outputs Y1, Y2 and Y3 HIGH) and close the by-pass valve V1 ( set CE123 output Y1 LOW). The water will now follow through tanks 1 and 2 and back to the reservoir. Note that the CE111 is equipped with fluid overflow pipes which prevent the water spilling over the edges of the tanks. Part 4. Manual Control
In this section you are asked to fill tank 2 and tank 1 and then empty the tanks back into the reservoir. This is a typical PLC control cycle and will help you to understand the way in which logical sequences operate. Note in the cycle given below that valve V2 stays open all the time and the flow input is controlled from the by-pass valve V1. This is to avoid the pump operating with both valves closed. a)
Open valve V1, V2, V3 and V4
b)
Start the pump and close valve V1
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c)
Close valve V4
d)
When level indicator L2 lights up then close valve V3
e)
When level indicator L4 lights up then stop the pump (set Y0 low)
f)
Drain the tanks by opening valves V3 and V4
Conclusion
At the conclusion of this experiment you should f eel familiar with the inputs and outputs of the CE111. I n addition, you should be able to manually operate the CE111 valves and pump from the CE123 Trainer, and perform basic control sequences manually.
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Experiment 2: Basic Level Control (Tank 1)
Object
To use the CE111 in order to control the pump action and illustrate basic level control using a PLC. Apparatus
CE111 PLC Process Trainer CE123 PLC Trainer and suitable PC (A printer may be needed to record results) Procedure Part 1a. Set Up: Connect the CE123 and CE111
See “Initial Setup” on page 8. Part 1b. Set Up: Start the PLC software
Refer to the CE123 PLC Trainer manual. Part 2. Connect Inputs and Outputs
Connect the inputs and outputs between the CE111 to the CE123. See “Connection of Inputs and Outputs” on page 9. Part 3. Test the System
Turn on the power on the CE123 and set all the outputs to logic ‘0’ using the manual s witches. The CE111 should now be inactive. Ensure that X5 is set HIGH (reservoir float switch). If not, top up the fluid level. Note: During operation the indicator light F1 and the corresponding controller lamp will flash at a rate determined by the fluid flow rate. This i s because the flow rate sensor pr ovides a pulsed output. A consequence of this i s that when the fluid flow stops the sensor F1 may be ill uminated or not depending upon the point in the cycle at which the sensor stops rotating. The valves are OPEN when they are set HIGH (logic ‘1’) and CLOSED when set L OW (Logic ‘0’). Open and close each of the valves in turn and an audible click should be heard as they operate. Part 4. The Basic Pump Control
Use the CE123 software to create the ladder diagram shown in Figure 8. This logic control circuit checks the reservoir level, and the state of the input X6 opens the by-pass valve (V1) and then switches on the pump (P1). The control sequence is activated by setting input X6 to ‘1’ using the CE123 control switches. Use the software to transfer the programme to the CE123. Run the programme and set the input and output switches on the CE123 to external. The valve V1 should open and then pump P1 will start. This is a basic form of interlock system in PLC systems whereby certain events are prevented from happening before a set of other events has occurred. In the CE111, the pump may be damaged if it is run with both V1 and V2 closed. This programme segment shows how to prevent this happening in one simple set of circumstances. Part 5. Basic Level Control
Use the CE123 software to create the ladder diagram shown in Figure 9. Set the pump speed to the maximum setting. Use the CE123 software to load the programme to the CE123. Start the programme by switching the CE123 to RUN using the switch mounted on the back of the CE123 and set the i nput and output switches on the CE123 to external.
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NOTE
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If the PLC programme appears not to work, first check the connections between the CE111 and the CE123. Next check the ladder diagram. Also check that there is sufficient fluid in the reservoir to keep L5 HIGH at all t imes. If the reservoir becomes low during the cycle, it will be detected in the logic programme.
This logic controller circuit is started if th e input X6 is set manually to ‘1’ and the reservoir sensor is high. It operates a level control cycle whereby valves V2 and V3 are opened and closed, according to the state of the L4 sensor in tank 1. The objective is to maintain the tank level in tank 1 around the high mark. Going through the ladder diagram rung by rung: Rung 1 starts the pump when X6 is high and, if the reservoir level is high, it also opens the by-pass valve if the feed to tank 1 is closed. Rung 2 when the pump is high (or the reservoir level is too low) the tank 2 valve is opened. (This is to drain water back to the reservoir and is not part of the control cycle). Rung 3 when the tank 1 high level indicator is low and the input X6 is high then the tank 1 feed is valve is opened. Rung 4 when the tank 1 high level indicator is hi gh the drain valve to tank 1 is opened. Part 6. Basic Level Control with Delay Timers
The control cycle in part 5 should oscillate rapidly between the two states. This can cause wear in the valves. To avoid this, change the last two rungs of your ladder diagram as shown in the ladder diagram in F igure 10. This programme will introduce delays in the control action for the two valves and reduce the speed of the control loop cycle according to the timer count values. Conclusion
Comment on the structure of the programme. You may find it useful to draw a simple flow chart that relates the actions on each rung with a logical action in a flow chart.
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Figure 8 Basic Pump Control
Figure 9 Basic Level Control
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Figure 10 Basic Level Control with Delay Timers
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Experiment 3: Level Control (Tank 1 and Tank 2)
Object
To use the CE123 in order to control the levels in the two tanks. Apparatus
CE111 PLC Process Trainer CE123 PLC Trainer and suitable PC, loaded with the correct sof tware. A printer may be needed to record results. Procedure Part 1a. Set Up: Connect the CE123 and CE111
See “Initial Setup” on page 8. Part 1b. Set Up: Start the PLC software
Refer to the CE123 PLC Trainer manual. Part 2. Connect Inputs Outputs
Connect the inputs and outputs between the CE111 to the CE123. See “Connection of Inputs and Outputs” on page 9. Part 3. Test the System
Turn on the power on the CE123 front panel and use the manual selectors to set all outputs to logic ‘0’. The CE111 should now be inactive. Ensure that X5 (the reservoir level indicator) is set HIGH, if it is not then top up the fluid reservoir. The valves are open when their inputs are set HIGH (logic ‘1’) and closed when set LOW (logic ‘0’). Open and close each valve in turn, an audible click should be heard as they operate. Part 4. Level Control for Tanks 1 and 2
Use the CE123 software to construct the ladder diagram programme shown in Figure 11. Use the CE123 software to load the programme to the CE123. Start the program by switching the CE123 to run using the switch mounted on the back of the CE123 and set the input and output switches on the CE123 to external.
NOTE
If the PLC programme appears not to work, first check the connections between the CE111 and the CE123. Next check the ladder diagram. Also check that there is sufficient fluid in the reservoir to keep L5 HIGH at all times. If the reservoir becomes low during the cycle, it will be detected in the logic programme.
With the programme running, the input X6 initiates the control sequence and input X7 disables the control. Note that a different system is used in this programme to prevent rapid cycling of the valves between open and closed. This is the function of the timers. Conclusions
Compare the method used to delay the control loop speed of response with the method used in Experiment 2. If you can, develop your own system for controlling the speed at which the valves cycle through the control loop.
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Figure 11 Level Control of Tanks 1 and 2
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Experiment 4: Tank Filling Sequence
Object
To use the CE123 to show how a simple filling sequence operates. These are commonly used in industry where a fixed sequence of events must be carried out in res ponse to a signal from another part of a system. This occurs in all branches of the manufacturing industry. The example here is taken from an oil industry example, in which a request from a dispatch centre (input X6 in the experiment) starts the filling of the two tanks. A further external input (X7) resets the process and empties the tanks. Apparatus
CE111 PLC Process Trainer CE123 PLC Trainer and suitable PC, loaded with the correct sof tware. A printer may be needed to record results. Procedure Part 1a. Set Up: Connect the CE123 and CE111
See “Initial Setup” on page 8. Part 1b. Set Up: Start the CE123 PLC software
Refer to the CE123 PLC Trainer manual. Part 2. Connect Inputs and Outputs
Connect the inputs and outputs between the CE111 to the CE123. See “Connection of Inputs and Outputs” on page 9. Part 3. Test the System
Turn on the power on the CE123 front panel. Use the manual selectors to set all outputs to logic ‘ 0’. The CE111 should now be inactive. Ensure that X5 (the reservoir level indicator) is set HIGH. If it is not, top up the fluid reservoir. The valves are open when their inputs are set HIGH (logic ‘1’) and closed when set LOW (logic ‘0’). Open and close each valve in turn. An audible click should be heard as they operate. Part 4. Tank Filling Sequence
Use the CE123 software to construct the ladder diagram shown in Figure 12. Use the CE123 software to load the programme to the CE123. Run the programme by using the run switch on the back of the CE123 and set the input and output switches on the CE123 to external.
NOTE
If the PLC programme does not work, then first check the connections between the CE111 and the CE123. Next check the ladder diagram. Also check that there is sufficient fluid in the reservoir to keep L5 HIGH at all times. If the reservoir becomes low during the cycle then it will be detected in the logic programme.
Start the control sequence manually by setting input X6. The logic control circuit then performs the task of first filling tank 1, then filling tank 2 and, finally, when tank 2 is full, refilling tank 1. When both tanks are full the process stops. To empty the tanks at the end of the cycle, or to stop the process mid-cycle, use X7. Conclusions
The experiment illustrates the form of filling sequences used in industry where a sequence of activities occurs until a set of desired conditions are met. In this case, the sequence corresponds with a tank filling sequence used in batch processing of petrol/chemicals. The inputs X6 (starting the sequence) and X7 (stopping the sequence) represent external control
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signals from another part of a process. Note the use of internal memory registers M 1, M2, to keep a record of the actions in the process.
Figure 12 Tank Filling Sequence
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Experiment 5: Simulated Batch Sequencing
Object
The object of this experiment is to use the CE123 to show how a batch process s equence operates. These are commonly used industries where repeated cycles must be carried out at specific times. This occurs in all manufacturing industries, although the specific example given here is from the chemical process industries. The experiment simulates a chemical reaction control sequence where the objective is to fill tank 2 with a mix of two chemicals (A and B) and to wait a fixed time until a reaction has taken place. After the reaction time (a period specified by timers) the logic control programme empties and flushes the tanks before beginning the s equence again. Apparatus
CE111 PLC Process Trainer CE123 PLC Trainer and suitable PC, loaded with the correct sof tware. A printer may be needed to record results. Procedure Part 1a. Set Up: Connect the CE123 and CE111
See “Initial Setup” on page 8. Part 1b. Set Up: Start the PLC software
Refer to the CE123 PLC Trainer manual. Part 2. Connect Inputs and Outputs
Connect the inputs and outputs between the CE111 to the CE123. See “Connection of Inputs and Outputs” on page 9. Part 3. Test the System
Turn on the power on the CE123 front panel and set all outputs to logic ‘0’ using the manual selectors. The CE111 should now be inactive. Ensure that X5 (the reservoir level indicator) is set HIGH. If it is not, top up the fluid reservoir. The valves are open when their inputs are set HIGH (logic ‘1’) and closed when set LOW (logic ‘0’). Open and close each valve in turn. An audible click should be heard as they operate. Part 4. Simulated Batch Sequencing
Use the CE123 software to construct the ladder diagram shown i n Figures 13, 14, 15 and 16. Use the CE123 software to transfer the programme to the CE123. Run the programme by using the run switch on the back of the CE123 and set the input and output switches on the CE123 to external.
NOTE
If the PLC programme does not work, first check the connections between the CE111 and the CE123. Next check the ladder diagram. Also check that there is sufficient fluid in the reservoir to keep L5 HIGH at all times. If the reservoir becomes low during the cycle, it will be detected in the logic programme.
The control sequence is started manually by setting input X6 to logic ‘1’. To stop the process mid-cycle, use X7. The logic control circuit simulates the following tasks: a)
Tank 1 is filled with chemical A
b)
Tank 1 is emptied into tank 2
c)
Tank 1 is filled with chemical B Page 21
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d)
Tank 1 is emptied into tank 2 until tank 2 is full
e)
The process waits 30 seconds on timer T0 for a chemical reaction to take place in tank 2 between chemicals A and B.
f)
Tank 2 valve opens and empties the result of the reaction out of the tank.
g)
Wash Tanks 1 and 2. To do this, fill them up to their upper limits and then drain them.
The process repeats itself. The reset button X7 can be used t o reset the programme at any s tage in the sequence. The logic programme is started by setting X6 to HIGH. If X6 is set low at any stage, the programme is held at its current state until either X6 or X7 is set HIGH. Part 5. Monitoring the Timers and Internal Memory Flags
The experiment uses timers are internal memory registers M. Use the monitor feature of the CE123 PLC software to trace how the memory registers are used and the t imer actions. Conclusions
This sequence is a fairly complex logical control sequence and is typical of repetitive sequences in manufacturing and process industries. If you have reached this stage with an understanding of the programme’s behaviour, you have reached a good level of knowledge of PLCs and their us e.
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Figure 13 Simulated Batch Sequencing (Steps 0 to 31)
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Figure 14 Simulated Batch Sequencing (Steps 32 to 54)
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Figure 15 Simulated Batch Sequencing (Steps 55 to 82)
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Figure 16 Simulated Batch Sequencing (Steps 82 to 96)
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SECTION 3.0 Results
As an aid to the course instructor and the laboratory assistant, the ladder diagrams (project files) used in the experiments are supplied on a disk that is shipped with the CE111. Keep this disk in a s ecure place. To use the ladder diagrams, insert the disk into your PC. Copy the project files to a suitable folder on your hard drive. Start the CE123 PLC Trainer software. Use the software to access the project files. The relevant ladder diagram (project file) names are given in Table 2.
Experiment
Project Files
1
None Needed
2
Exp 2 Basic Level Control Exp 2 Basic Level Control with Timers Exp 2 Basic Pump Control
3
Exp 3 Level Control of Tanks 1 & 2
4
Exp 4 Tank Filling Sequence
5
Exp 5 Simulated Batch Sequencing
Table 2 Experiment Project Files
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APPENDIX A:
Useful Textbooks
Programming Manual II
by Mitsubishi
Programmable Controllers: Operation and Application
by Ian G Warnock Published by Prentice Hall, 1988 ISBN 0137300379
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APPENDIX B:
Blank Experiment Panels
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