Beginners Guide to PLC Programming
Contents
1. LAD 2 MAIN Total Rungs in File 35 0008 0009 0010 0011 0012 Run Infeed System in Conveyor Auto Mode MS1 B3 0 2 0 3 0 e 25 1746 0 16 0 3 0 XIC 2 23 Ensure there are no parts in the machine to start the drilling eyele Placed in Placed in Part at Part No Part X Axis Y Axis Home Cleared In PSC31 PSC32 PSC33 PSC34 Machine 1 2 6 1 2 7 1 2 8 1 2 9 B3 0 4 B3 0 4 XIC 2 11 1746 1 16 1746 1 16 1746 I 16 1746 I 16 Hold Part Drilling Spindle in Place Stop Gate Raised Machine SOL11 SOL12 PRS35 at Home 0 3 5 0 3 6 1 2 10 B3 0 5 B3 0 5 XIC 2 11 1746 0716 1746 0716 1746 I 16 2 15 2 12 No Part End of System in In Machine Machine Auto Mode Machine at Home Cycle B3 0 2 B3 0 4 B3 0 5 B3 0 8 ee 2 5 2 9 2 10 2 19 Machine in Cycle B3 0 6 C es 211 Machine in Cycle B3 0 6 ee B3 0 6 XIC 2 11 2 12 2 15 2 10 2 17 2 18 2 19 2 28 2 31 Lower the stop gate to stop the part under the spindle Drilling Machine Stop Gate in Cycle SOL12 B3 0 6 0 3 6 2 11 1746 0 16 0 3 6 XIO 2 10 Supplementary recommendations that will help available at engineer and technician com How to Program RSView32 ebook 19 95 PLC Programming Pic Programming with RSLogix 500 ebook ASLogix 500 19 95 PLC Programming PLC Programming How To Troubleshoot with with RSLogix 5000 With A PLC RSLogix 50002. B3 0 2 is the same bit as COIL4 in our generic program Cross Reference The RSLogix program shows cross referencing The number 2 5 under the first instruction means that the output or coil for that address is found in file 2 rung 5 2 is the first and default data file of a ladder in RSLogix The output O 3 2 shows that its contacts are found on rungs 6 7 and 25 of data file 2 Rung Numbers RSLogix starts with rung 0000 the generic program starts with rung 1 so the rung numbers shown in the RSLogix program will be one less than the rung numbers in the generic program Logic Flow Bits that are true in RSLogix are shown with a green highlight This RSLogix ladder printout above is a snapshot showing the system in automatic mode the part is in place and the drill bit is being lowered There are no faults Other Information RSLogix will provide a variety of information regarding the program and hardware have included those pages here Beginner s Guide to PLC Programming 39 Copyright 2013 Modern Media amp Automation LLC engineer and technician com DRILPRES RSS LAD 2 MAIN Total Rungs in File 35 EmergStop Guard in Start Stop Cleared Place System System System CR1 LS26 Fault PB2 PB3 1 1 4 1 2 4 B3 0 12 1 1 14 1 1 2 0000 230 1746 I 16 1746 I 16 1746 I 16 1746 1716 System Running B3 0 0 2 0 System Running B3 0 0
3. s Guide to PLC Programming 7 Copyright 2013 Modern Media amp Automation LLC engineer and technician com proceed to drill a hole in the part After the hole has been drilled and the spindle has retracted to its home position the clamp will release the stop gate will raise and the part will exit The cycle then repeats itself for each part that comes down the line Here is a more detailed explanation of the drilling process When the machine starts the stop gate lowers and the part is moved into position by the main conveyor Optical sensors photoeyes determine when the part is in place When the part is positioned correctly a clamp extends to hold the part in place Beginner s Guide to PLC Programming 8 Copyright 2013 Modern Media amp Automation LLC engineer and technician com The spindle of the drill press is lowered and the hole is drilled in the part A sensor in the drill press spindle tells the PLC when the spindle has reached the end of its travel After the hole is drilled the spindle retracts the clamp retracts the stop gate is lifted and the part is carried out of the machine by the main conveyor Beginner s Guide to PLC Programming 9 Copyright 2013 Modern Media amp Automation LLC engineer and technician com The Program Now that you understand what has to be done and how it is to be accomplished by the mechanical equipment you can begin writing the program The
4. SS B3 0 0 XIC 2 0 2 3 2 4 2 5 EmergStop Pilot Cleared Light CR1 Test Time 1 1 4 TON 0001 m Timer On Delay EN gt _ Timer T4 0 1746 I 16 Time Base 1 0 DN Preset 2 lt Accum 2 lt T4 0 DN XIO 2 2 EmergStop Pilot Pilot Cleared Light Light CR1 Test Time Test 1 1 4 T4 0 DN B3 0 1 0002 2 1 B3 0 1 XIC 2 3 2 7 2 14 1746 1 16 2 20 2 22 2 27 2 30 Indicate the system is operational O OO O O O O OOO a System System Running Running PL20 B3 0 0 0 3 7 0003 lle 2 0 1746 0716 Pilot Light Test B3 0 1 20 DRILPRES RSS LAD 2 MAIN Total Rungs in File 35 System in System in System Auto Mode Manual Running SS4 Mode B3 0 0 1 1 3 B3 0 3 0004 2 0 B3 0 3 XIC 2 6 2 15 2 16 1746 I 16 2 18 System in System Auto Mode System in Running SS4 Auto Mode B3 0 0 1 1 3 B3 0 2 0005 a r 2 0 B3 0 2 XIC 2 6 2 8 2 11 1746 1 16 2 13 Run Drill System in Press Auto Mode MS5 B3 0 2 0 3 2 0006 n B EEE CC 2 5 1746 0 16 System in Start Stop O0 3 2 XIC 2 6 2 7 2 25 Manual Press Press Mode PB6 PB7 B3 0 3 11 5 1 1 6 ins 2 4 1746 1 16 1746 I 16 Run Drill Press MS5 0 3 2 1746 0 16 2 6 Indicate the drill press is running Drill Run Drill Press Press Running MS5 PL21 0 3 2 0 3 8 0007 n SE _ 1746 0 16 1746 0 16 2 6 Pilot Light Test B3 0 1 22 DRILPRES RSS
5. text in the fixed font is basically the information that you would see if you were looking at the monitor of the computer or a printout In actual practice the fonts used in PLC software vary widely For the purposes of this book we want to easily differentiate the program logic from our explanations of the logic A series of asterisks indicates a rung comment This is descriptive text added to the program and is seen on the programming monitor but has no affect on the logic For purposes of this manual have placed additional explanations between rungs Use a title to name the program and include any general information AUTOMATIC DRILL PRESS MACHINE CONTROL PRODUCTION LINE 3 REVISION 2 Machine Safeties It is best to start a program by evaluating any safety switches and setting a master bit This type of bit is what we call an internal coil It has no hardwired connection to the outside world In this case a latch is used to set an internal System Running bit The latch is accomplished by putting a normally open contact around the Start System pushbutton input If the emergency stop is clear and the machine guard is in place and there is no system fault the operator may press the start button to set the latch If the stop button is pushed or a previous conditions ceases to exist the System Running latch will drop out Most of the time the order of the bits in a rung doesn t matter We could have rearra
6. Beginner s Guide PLC Programming by Neal Babcock How to Program a PLC Programmable Logic Controller Beginners Guide To PLC Programming How to Program a PLC Programmable Logic Controller By Neal Babcock Industrial Automation Series engineer and technician com Beginner s Guide to PLC Programming Copyright 2013 Modern Media amp Automation LLC engineer and technician com Table of Contents Introduction to PLUGS ctcaricit sce Seed Ladder ele eae neee eee err ee ee a rer The Dialect of PUG Sree ete piacere area ctels Equivalent 0 eee ee or eee Scan TMe cere Sener ener E nen nee renee earnest en The Automated Drill Press Sequence of Operation c ccceccseeeeeseeeeeeeeseeeeeeesaeeeeeees Operator Station asistgs ececeatsedeiasnaitesespae ineysiereteds te tiertadedaes MO LE SUING ie cesia aa iar e ERENER ATRE EE PUIS n a E E E JUNG occa cecicssdncacoite selma sainepedemtsc epaavekacee lassie eaveseantudemeseaige Internal Coils asd iaeeentet acetic id essere cnenteniedies nceaeeian miedo The ProgtaMs sisisi anana Machine Safeties oss sca seca etiam cad PMU LAW WSSU csscees occ ie tic peer aenenes encase ckeeeee eens Indicate The System Is Operational cceeeeeeeeeeees Machine Operation Mode cccceeeeeeeeeeeeeteeeeeeeeentaeeeteees Run The Spindle Drive Motot ccccceeesscceeeesseeeeeeeeeees Indicate The Spindle Drive Is Running eeeeeeeeees
7. Inc Beginner s Guide to PLC Programming Copyright 2013 Modern Media amp Automation LLC engineer and technician com
8. Run The Infeed Conveyor ccccceeesceceeeeseceeeeessieeeeeeeeees Ensure There Are No Parts In The Machine Ensure All Components Are At HOMG eeeeeeeeeeeeeeeeees Begin The CVC acai cecactiya cei enteseetsnes dence tes Jacecnade netemsanncneeene Lower The Stop GANS eccisec cascdeecscrixieccuseanstsatiencenteseenieceleanedice Run The Main Conveyor is sicccscccccssssscccacsasereereadeeenasense Indicate The Part Is In Place Clamp The Part In Place siccscpecexesciiececter een tuacaccs dutta Lower The Spindle ssneneeenneeeeeerrneerrrreereersrrrrserrrr rreren Drilling Operation Is Complete c cceeeeeceeeeeteeeeeeeeeees Return The Spindle To Its Home Position cceeee Machine Cycle Is Complete cceceeeeeeeeeeeeeeeeeteeeenees Fault Detection And System Diagnostics cceee Personnel Safety Guard DOol ccccceeeessceeeeesteeeeeeeenees Low Compressed Air Pressure ccccceeecteeereeeeesteeeeetees Motor Starter Overload wisaitcdsetenicicateniehsciedsaents eecehtnlerenaciede Latch The Motor Overload Detection ccceceeeeeeeeeee Indicate A Motor Overload Condition cceeeeeeeeeeees Jammed Part Detection scccsiinc dest sasccceantilevetcstieeaetdeastelencies Latch The Part Jammed Detection n Indicate A Part Jammed Condition eeceeeeteeeeeeteeeees Monitor The Drill Time 0 eeeeseeeceeee ener eeeeeeeee
9. a good idea to keep track of the compressed air pressure The machine will not operate properly if there is insufficient air pressure You can put it on a fairly long time delay because you don t care about momentary drops in pressure like a second or two But when it does drop beyond the lower limit for enough time you want the machine to stop You also want it to latch so you know why the machine stopped running The air pressure could come back up before the operator sees the pilot light and he would be left scratching his head The latch is reset by the Reset System pushbutton xxx Detect abnormally low compressed air pressure AirPressr Air Normal Pressure PS27 Abnormal INPUT27 TIMER27 22 4SEC Air Reset Pressure System Abnormal PB1 TIMER27 INPUT1 gt xxx Indicate abnormally low air pressure Air Low Air Pressure Pressure Abnormal PL26 TIMER27 OUTPUT26 23 t OUT Pilot Light Test corr2 77 Beginner s Guide to PLC Programming 28 Copyright 2013 Modern Media amp Automation LLC engineer and technician com Motor Starter Overload If the auxiliary contacts in the motor starters don t pull in after one second there is some kind of problem You have to look at e
10. ach one individually 25 xxx x The starter is assumed to be overloaded if the aux contact does not pull in after 1 second RunInfeed Conveyor MS1 OUTPUT1 Run Main Conveyor MS2 ouTPUT2 Run Drill Press MS5 OUTPUTS InfedConv Infeed Running Conveyor MS1AUX Overload INPUT20 TIMER1 Se a ee 1SEC Main Conv Main Running Conveyor MS2AUX Overload INPUT23 TIMER3 Sg ee ee ee ee 1SEC DrillPres Drill Running Press MS5AUX Overload INPUT24 TIMER5 Se ee ee 4 1 EC lt Beginner s Guide to PLC Programming Copyright 2013 Modern Media amp Automation LLC engineer and technician com 29 The Automated Drill Press in RSLogix 500 The most popular and most widely used manufacturer of PLCs is Rockwell Automation who produces the Allen Bradley MicroLogix and SLC series of PLCs The MicroLogix and SLC families of processors and I O modules are all programmed using Rockwell s proprietary software known as RSLogix used a generic style of ladder logic in the first part of the book to explain the fundamentals of ladder logic This style was chosen because it applies to all types of PLCs To give you a better understanding of how the program would look in a real world situation have included the same Automated Drill Press program as it would appear if it were written in Allen Bradley s RSLogix Here is an example Run Drill System in Press Au
11. ebook ebook Cate ae 19 95 19 95 tow te Penge os Alen Pafe AC w Pub M he Dyane al mmc Peder wth Riiaga 00 arai Aliagas 1000 by Nesi Badcock Beginner s Guide to PLC Programming Copyright 2013 Modern Media amp Automation LLC engineer and technician com PLC is a trademark of the Allen Bradley Company THE FOLLOWING ARE TRADEMARKS OF ROCKWELL AUTOMATION INC Allen Bradley MicroLogix PanelView RSLinx RSLogix RSLogix 500 SLC 500 THE AUTHOR OR THE PUBLISHER OF THIS BOOK IS IN NO WAY AFFILIATED WITH ROCKWELL AUTOMATION INC Disclaimer THE AUTHOR INTENDS THIS DOCUMENT TO BE ADVISORY ONLY ITS USE IN INDUSTRY OR TRADE IS ENTIRELY VOLUNTARY THIS DOCUMENT IS PROVIDED BY THE VENDOR AS IS AND ANY EXPRESSED OR IMPLIED WARRANTIES INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FORA PARTICULAR PURPOSE ARE DISCLAIMED IN NO EVENT SHALL THE VENDOR OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT INDIRECT INCIDENTAL SPECIAL EXEMPLARY OR CONSEQUENTIAL DAMAGES INCLUDING BUT NOT LIMITED TO PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES LOSS OF USE DATA OR PROFITS OR BUSINESS INTERRUPTION HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY WHETHER IN CONTRACT STRICT LIABILITY OR TORT INCLUDING NEGLIGENCE OR OTHERWISE ARISING IN ANY WAY OUT OF THE USE OF THIS DOCUMENT EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE Courtesy of Rockwell Automation
12. eeeeeeneeeeees Summarize The Fault Conditions cccceeeeeeeeeeeneeeeeee 13 Marks Of A Well Written Program cceeeeeeeeeeeees General PLC TIPS soenan e aae The Automated Drill Press in RSLogix 500 Beginner s Guide to PLC Programming Copyright 2013 Modern Media amp Automation LLC engineer and technician com Nearly all the industrial equipment that you find in a modern manufacturing facility shares one thing in common computer control The most commonly used controller is the PLC or the Programmable Logic Controller using a programming language called Ladder Logic The language was developed to make programming easy for people who already understood how switches relay contacts and coils work Its format is similar to the electrical style of drawing known as the ladder diagram Originally there were only a few functions available in this language but as times have progressed many more higher level functions have been introduced We are going to stick to the basic commonly used functions here Also this text will not replace the user s manual that comes with a PLC but it will give you a big head start if you have never programmed a PLC This course is intended to provide an introduction to the programming methods used in PLCs and give the reader a solid basic understanding of the language of Ladder Logic After you complete this course you may be interested in learning about hardware specific sof
13. nged any of the bits in this rung though we would still have to put the latch around the Start pushbutton The PLC wouldn t care and the output coil would still respond the same However to make the rung easier to read try to place bits from left to right in order of importance If the E Stop is not cleared then nothing else should matter anyway Having the safety guard in place is more important than a system fault Now if those requirements have been met we can press the start button And we don t care about the stop button until we have pushed the start button Beginner s Guide to PLC Programming 13 Copyright 2013 Modern Media amp Automation LLC engineer and technician com Run The Spindle Drive Motor This rung turns on the drill press spindle motor It will come on immediately in automatic mode but it can also be controlled by the Start Press and Stop Press switches in manual mode xxxx x Run the spindle drive motor of the drill press manual mode is provided to allow ease of set up System in Auto Mode corL4 PM ee pene ener SystemIn Start Stop Manual Press Press Mode PB6 PB7 COILS INPUT6 INPUT7 a o na Run Drill Press MS5 OUTPUTS Beginner s Guide to PLC Programming Copyright 2013 Modern Media amp Automation LLC engineer and technician com A Run Drill Press MS5 OUTPUT5 17 Low Compressed Air Pressure It is
14. rogram Normally Closed Contact This is an inverted normally open contact When used with a hardwired input this instruction is true until there is a voltage applied to the input It then goes low or off and becomes false It also can be used with an internal coil becoming true when the coil is off and becoming false when the coil is on Beginner s Guide to PLC Programming 2 Copyright 2013 Modern Media amp Automation LLC engineer and technician com The Automated Drill Press Now let s jump right into a project The best way to learn a programming language is to look at a real world example However before you can do any programming you must have a clear understanding of how the machine works Let s say a furniture manufacturer needs to drill a 3 8 hole in a certain spot on a piece of wood The entire process needs to be automatic The mechanical and electrical engineers bring you an isometric drawing like the one shown here Mechanical details have been omitted for clarity as is often the case in a concept drawing The main conveyor will transport the part into the machine where the part will meet a pneumatically actuated stop gate At that time another pneumatic cylinder will actuate a clamp that will push the part back against the conveyor wall This will hold the part in place during the drilling process Photocells will verify that the part is in position the spindle will lower and Beginner
15. tanding of the structure of this type of programming In the real world of industrial automation the methods presented in this document may be all that many people will ever need to know The Dialect of PLCs Let s define some terms and symbols BIT an address within the PLC It can be an input output or internal coil among others RUNG A section of the PLC ladder program that terminates in an output function of some type HARDWIRED INPUT a physical connection to the PLC from an input device switch or sensor etc A hardwired input is labeled INPUT in our example HARDWIRED OUTPUT a physical connection from the PLC to an output device relay or pilot light etc A hardwired output is labeled OUTPUT in our example INTERNAL COIL This is a programmable bit used to simulate a relay within the PLC The internal coil has no connection to the outside world It does not connect to an output card Internal coils are used to store information The contacts of this relay can then be used multiple times in other parts of the program An internal coil is labeled COIL in our example Normally Open Contact When used with a hardwired input this instruction is off until there is a voltage applied to the input The bit address then goes high or on and the instruction becomes true It works the same way when it has the same address as an internal coil except that the coil must be turned on by logic in the p
16. to Mode MS5 B3 0 2 O w2 0006 2 5 1746 0716 System in Start Stop O 3 2 XIC 2 6 2 7 2 25 Manual Press Press Mode PB6 PB7 B3 0 3 1s 16 2 4 1746 I 16 1746 116 Run Drill Press MS5 0 3 2 1746 0 16 2 6 will give you a brief outline of the differences between the generic format of ladder logic that used and RSLogix s format First though the address descriptions and the rung comments are the same in the RSLogix program as they are in the generic program Despite what the numbers say under the instruction System in Auto Mode is the same bit here as the System in Auto Mode is in the generic program Beginner s Guide to PLC Programming 38 Copyright 2013 Modern Media amp Automation LLC engineer and technician com Outputs Allen Bradley labels their outputs starting with a capital O whereas we used output in the generic program In the rung above O 3 2 is the same bit as OUTPUTS in our generic program 1746 O0 16 indicates the type of output module Inputs Allen Bradley labels their inputs starting with a capital I whereas we used input In the rung above I 1 5 is the same bit as INPUTS in our generic program 1746 I 16 indicates the type of input module Coils internal bits Allen Bradley labels most their internal coils starting with a capital B3 whereas we used out In the rung above
17. tware and programming techniques Modern Media offers a book entitled PLC Programming Techniques How to Program an Allen Bradley SLC 500 with Rockwell Automation s RSLogix This ebook shows step by step how to create a program from scratch in Allen Bradley s RSLogix 500 To learn more please visit engineer and technician com have summarized the terms and techniques you need to know if you are going to work with ladder logic It is not a comprehensive summary as that would take volumes of text but if you are just starting out the information in this book will be very helpful Every PLC programmer no matter what skill level must have learned the principles described in this book at one point in time There is simply no way around it have included a program for a simple machine that lets you really understand how Ladder Logic works To effectively write a program or even edit one the programmer must know how to visualize the effects of the changes he will make In other words you have to be able to look at the logic on paper and imagine how it will work when it is entered into the PLC This course will teach you how to do that Beginner s Guide to PLC Programming 1 Copyright 2013 Modern Media amp Automation LLC engineer and technician com There are many types of PLCs and differences among PLCs but what is discussed here should be common to all types After you read and understand this you will have a clear unders
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