Sample. Pearson BTEC Levels 4 Higher Nationals in Engineering (RQF) Unit 15: Automation, Robotics and Programmable Logic Controllers (PLCs)

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1 Unit WorkBook 2 Lvl 4 ENG U5: Autoation, Robotics and Prograabl Logic Controllrs (PLCs) 28 UniCours Ltd. All Rights Rsrvd. Parson BTEC Lvls 4 Highr Nationals in Enginring (RQF) Unit 5: Autoation, Robotics and Prograabl Logic Controllrs (PLCs) Unit Workbook 2 in a sris of 2 for this unit Larning Outco 2 PLC Progra Dsign Pag of 24

2 Unit WorkBook 2 Lvl 4 ENG U5: Autoation, Robotics and Prograabl Logic Controllrs (PLCs) 28 UniCours Ltd. All Rights Rsrvd. Prograing Languag Signal Typs Signals fro snsors, and to output dvics, can b in on of thr fors; Analogu a continuously varying signal aitud with ti. Discrt basically just on and off Digital pulss with flat tops and bottos Th CPU insid th PLC will, howvr, only rspond to digital signals of a particular aitud. Usually volts to rprsnt logic, and +5 volts to rprsnt logic. This ans that input and output signals ust b anipulatd so that thy ar prsntd in th corrct for for th CPU. This is a job for th PLC input/output units. Figur : Currnt sourcing and currnt sinking Whn th PLC input unit supis currnt to th input dvic, w tr this currnt sourcing. Whn it is th input dvic itslf that supis th currnt to th input unit, w tr this currnt sinking, as in Figur. To convrt an analogu signal into a digital signal w us an ADC (analogu-to-digital convrtr). Pag 4 of 24

3 Unit WorkBook 2 Lvl 4 ENG U5: Autoation, Robotics and Prograabl Logic Controllrs (PLCs) 28 UniCours Ltd. All Rights Rsrvd. Figur 2: Analogu-to-digital convrsion Figur 2 shows an 8-bit ADC. Th analogu signal is input to th ADC, which thn convrts th signal aitud at ach ont in ti into a digital cod. For an 8-bit ADC thr ar 28 = 256 possibl digital cods to rprsnt th input signal. Ths will rang fro (zro) to (255). Should th analogu input signal vary btwn V and V thn this will giv us a rsolution of /255, which is around 4 V. Thrfor, is th input signal incrasd by 3 V thr will b no chang in th digital output cod. If th input signal incrasd by 8 V thn this will caus th digital output to incras by two stps. Should w us an ADC with 6 bits thn thr will b 26 possibl digital cods i.. 65,536 of th. In this cas, th rsolution will b /65,535, which is around.5 V. Thrfor, th rsolution will iprov (gt sallr) if w us an ADC with a gratr nubr of bits. Pag 5 of 24

4 Unit WorkBook 2 Lvl 4 ENG U5: Autoation, Robotics and Prograabl Logic Controllrs (PLCs) 28 UniCours Ltd. All Rights Rsrvd. Nubr Systs Th basic typs of nubr w dal with rgularly in nginring ar: Natural Evryday positiv whol counting nubrs (i..,, 2, 3, 4, 5, ) Intgr Siilar to Naturals, but ngativs ar allowd (i.. -3, -2, -,,, 2, 3, ) Rational Can b xprssd as a fraction of two intgrs ( not allowd in dnoinator, i.. 9 5) Irrational - Can NOT b xprssd as a fraction of two intgrs (i.. 2 ) Ral ANY quantity along a continuous lin (i ) Cox Hav ral and iaginary coponnts. Rad or on ths latr Binary Bas 2 Octal Bas 8 Dnary Bas (what you r ost usd to) Duodcial (also known as Doznal) Bas 2 Hxadcial Bas 6 Coon nubr systs ncountrd in nginring ar: To work fficintly in odrn nginring, you nd to b abl to not only apprciat ach of ths nubr systs but also convrt btwn th. You can always chck your answrs by using th Windows Calculator (click on Viw thn Prograr). Using th calculator is fin, but Assignnt asks that you donstrat knowldg of th chanics of ths convrsions. Lt s look at ach syst first and thn work out how to go about th convrsions in dtail. Binary Syst (Bas 2) Th Binary syst only uss two digits, and (hnc th tr Binary). Lt s look at a tat for th Binary syst 𝟐𝟕 28 s 𝟐𝟔 64 s 𝟐𝟓 32 s 𝟐𝟒 6 s 𝟐𝟑 8 s 𝟐𝟐 4 s 𝟐𝟏 2 s 𝟐𝟎 s Octal Syst (Bas 8) Th Octal syst uss ight digits, through to 7 (hnc th tr Octal). Lt s look at a tat for th Octal syst 𝟖𝟕 𝟖𝟔 2,97,52 s 262,44 s Pag 6 of 24 𝟖𝟓 32,768 s 𝟖𝟒 4,96 s 𝟖𝟑 52 s 𝟖𝟐 64 s 𝟖𝟏 8 s 𝟖𝟎 s

5 Unit WorkBook 2 Lvl 4 ENG U5: Autoation, Robotics and Prograabl Logic Controllrs (PLCs) 28 UniCours Ltd. All Rights Rsrvd. Dnary Syst (Bas ) Th Dnary syst uss tn digits, through to 9 (hnc th tr Dnary). Lt s look at a tat for th Dnary syst (which you got usd to as a child) 𝟏𝟎𝟕 illions 𝟏𝟎𝟔 illions 𝟏𝟎𝟓, s 𝟏𝟎𝟒, s 𝟏𝟎𝟑, s 𝟏𝟎𝟐 s 𝟏𝟎𝟏 s 𝟏𝟎𝟎 s Duodcial Syst (Bas 2) Th Duodcial syst uss twlv digits, through to 9, thn T for tn and E for lvn (hnc th altrnativ tr Doznal, aning dozn). Lt s look at a tat for th Duodcial syst Hxadcial Syst (Bas 6) 𝟏𝟐𝟒 𝟏𝟐𝟑 𝟏𝟐𝟐 𝟏𝟐𝟏 𝟏𝟐𝟎 2,736 s,728 s 44 s 2 s s 𝟏𝟐𝟕 𝟏𝟐𝟔 𝟏𝟐𝟓 35,83,88 s 2,985,984 s 248,832 s Th Hxadcial syst uss sixtn digits, through to 9 us A through to F (hnc th tr Hxadcial). To oy 6 digits, w hav usd th lttrs A to F to rprsnt th nubrs to through to 5 rspctivly. Lt s look at a tat for th Hxadcial syst 𝟏𝟔𝟕 tc. 𝟏𝟔𝟔 tc. 𝟏𝟔𝟓 tc. 𝟏𝟔𝟒 65,536 s 𝟏𝟔𝟑 4,96 s 𝟏𝟔𝟐 256 s 𝟏𝟔𝟏 6 s 𝟏𝟔𝟎 s Rprsnting Nubrs in Each Syst If w wantd to rprsnt th vryday Dnary (bas ) nubr 2 in Binary forat thn w would hav to work fro lft to right in th Binary tabl 28 s in 2? Answr: so put in that cll 64 s in 2? Answr: so put in that cll 32 s in 2? Answr: so put in that cll 6 s in 2? Answr: so put in that cll 8 s in 2? Answr: so put in that cll and subtract th 8 fro th 2, laving 4 4 s in 4? Answr: so put in that cll and subtract th 4 fro th 4, laving Thr is nothing lft ovr hr, so w v finishd. W ay now writ 2 = 2. Pag 7 of 24

6 Unit WorkBook 2 Lvl 4 ENG U5: Autoation, Robotics and Prograabl Logic Controllrs (PLCs) 28 UniCours Ltd. All Rights Rsrvd. So xas of starting with a Dnary nubr and rprsnting it in th Binary, Octal and Hxadcial forats now follow Binary Syst (Bas 2) Octal Syst (Bas 8) 𝟐𝟕 𝟐𝟔 𝟐𝟓 𝟐𝟒 𝟐𝟑 𝟐𝟐 𝟐𝟏 𝟐𝟎 Dnary Exas Dnary Exas 𝟖𝟕 𝟖𝟔 𝟖𝟓 𝟖𝟒 𝟖𝟑 𝟖𝟐 𝟖𝟏 𝟖𝟎 ,67, Hxadcial Syst (Bas 6) Dnary Exas 𝟏𝟔𝟕 𝟏𝟔𝟔 𝟏𝟔𝟓 𝟏𝟔𝟒 𝟏𝟔𝟑 𝟏𝟔𝟐 𝟏𝟔𝟏 𝟏𝟔𝟎 5 F , F 2,, B E B C 2 Convrsions btwn bass: Dnary to Binary, Dnary to Octal and Dnary to Hxadcial convrsions ar all prford in th annr dscribd in th abov tabls. Binary to Dnary, Octal to Dnary and Hxadcial to Dnary convrsions ar all prford in th rvrs annr to thos convrsions alrady statd. That lavs us with six typs of convrsion to dal with: Binary to Octal Octal to Binary Binary to Hxadcial Pag 8 of 24

7 Unit WorkBook 2 Lvl 4 ENG U5: Autoation, Robotics and Prograabl Logic Controllrs (PLCs) 28 UniCours Ltd. All Rights Rsrvd. Hxadcial Addition To add hxadcial nubrs togthr w nd to think of th hx nubr syst ( to F) and start at th first digit to b addd to. W thn count to th right. Onc w ov right and pass F w rstart (loop) to th lft at until w hav countd th dubr of digits for th nubr w wish to add. Lt s clarify this procss by first of all listing th digits in th hx syst A B C D E F Now assu w wish to add th hx nubrs 8 and A. W start at 8 and thn ov right by A acs (i.. actual acs). Onc w hav ovd right by 7 acs w rach th nd, so nd to go back to th start and ov right by th raining 3 acs, which will tak us to 2. Sinc w hav loopd onc w not down that loop and thn appnd whr w ndd up, i.. that 2. Th answr in hx is thrfor 2 (on lot of 6 us 2 is 8, of cours, in dcial). Hr is a usful tabl for hx addition A B C D E F A B C D E F A B C D E F A B C D E F A B C D E F A B C D E F A B C D E F A B C D E F A B C D E F A B C D E F A B C D E F A A B C D E F B B C D E F A C C D E F A B D D E F A B C E E F A B C D F F A B C D E To us th tabl, locat th first digit to b addd in th orang row. Thn, locat th scond digit to b addd in th grn colun. Whr your slctions t is th answr to th addition. For xa, to add togthr hx 9 with hx A w locat th 9 in th orang row. Thn, locat th A in th grn colun. Whr ths two clls t is th answr i.. hx 3 in this cas. Hr is an xa us of th tabl for that particular probl A B C D E F A B C D E F A B C D E F Pag of 24

8 Unit WorkBook 2 Lvl 4 ENG U5: Autoation, Robotics and Prograabl Logic Controllrs (PLCs) 28 UniCours Ltd. All Rights Rsrvd A B C D E F A B C D E F A B C D E F A B C D E F A B C D E F A B C D E F A B C D E F A B C D E F A A B C D E F B B C D E F A C C D E F A B D D E F A B C E E F A B C D F F A B C D E Pag of 24

9 Unit WorkBook 2 Lvl 4 ENG U5: Autoation, Robotics and Prograabl Logic Controllrs (PLCs) 28 UniCours Ltd. All Rights Rsrvd. Counication Tchniqus Whn thr ar any inputs and outputs locatd at so distanc fro th ain PLC it is not practical or wis to run any cabls fro ths locations to th PLC. Instad w us input/output oduls in th rot aras and thn just run a twistd pair, scrnd coaxial or fibr cabl to th ain PLC, as in figur 3. Figur 3: Counicating with rot inputs/outputs So situations ight call for a nubr of slav PLCs counicating with th ain PLC, as in figur 4. Figur 4: Using a Mastr PLC to counicat with Slav PLCs Pag 5 of 24

10 Unit WorkBook 2 Lvl 4 ENG U5: Autoation, Robotics and Prograabl Logic Controllrs (PLCs) 28 UniCours Ltd. All Rights Rsrvd. Ntwork Mthods Modrn industrial ants ths days nd intrconnctions btwn PLCs, PCs, robots, tablts, obil phons and achinry. To achiv this counication nd a LAN (local ara ntwork) is intd within or btwn buildings. Such ntworks ay tak thr basic fors; star, bus and ring, as dpictd in figur 5. Figur 5: Star, Bus and Ring LAN topologis In th star for th astr, or host, is at th cntr, whras th slav trinals ar locatd at th pritr of th astr. Th astr polls th trinals, in turn, to s whthr thy wish to counicat with th astr. With th bus topology, all th trinals ar on a singl cabl, so a counications protocol is stablishd to nsur that only on trinal ay counicat with th astr at any on ti. With th ring topology, all th trinals ar again on a singl cabl, so a counications protocol is stablishd to nsur that only on trinal ay counicat with th astr at any on ti. A tokn is passd around th ring, so that any whichvr trinal posssss th tokn is th only on allowd to counicat. That trinal will thn rlas th tokn with th addrss its prfrrd trinal. Pag 6 of 24

11 Unit WorkBook 2 Lvl 4 ENG U5: Autoation, Robotics and Prograabl Logic Controllrs (PLCs) 28 UniCours Ltd. All Rights Rsrvd. Logic Functions AND function Considr a si lctrical circuit consisting of an apid voltag sourc, a load (drawn as a rctangular block), and two switchs, A and B, connctd in sris. Th switchs can b considrd as inputs to th circuit and th load as th output. A truth tabl is a convnint thod of dscribing th opration of th circuit (figur 6). dit Figur 6: AND circuit with its Truth Tabl and Laddr Diagra As th load only rcivs currnt whn both th A and B switchs ar closd, this circuit can b said to prfor a 2-input AND function. In th truth tabl an opn switch is rprsntd by a and a closd switch by a. An nrgisd load is rprsntd by a and an unnrgisd load by a. To th right of th truth tabl w s a Laddr Diagra, as it s known, for a PLC prograd to rprsnt th AND function. Th lftost vrtical bar is th positiv powr rail, and th rightost vrtical bar is th ngativ powr rail (or ground). Btwn ths powr rails w s a Rung, drawn horizontally. Th rung contains our input and output lnts. Hr thr ar thr lnts drawn. Input A is a norally opn switch (ys, it looks lik a capacitor, but in th PLC world this sybol is takn as a norally opn switch). Input B is anothr norally opn switch, and th Output is our load. In this cas th output is a otor, dnotd by th curly brackts in th PLC world. Whn both switch A AND switch B ar closd th otor will nrgis. You can produc your vry first PLC progra and ricat/siulat th laddr diagra in figur 6 by using a vry usful browsr-basd PLC siulator found hr at csiulator.nt (sign up is rquird, but it is saf). Go to its Hlp sction for usful vidos on how to us it. Pag 7 of 24

12 Unit WorkBook 2 Lvl 4 ENG U5: Autoation, Robotics and Prograabl Logic Controllrs (PLCs) 28 UniCours Ltd. All Rights Rsrvd. Laddr Progras Exa Us to dsign and siulat a laddr diagra for a si syst whr a norallyopn switch is prssd to driv a otor. Pag 22 of 24

13 Unit WorkBook 2 Lvl 4 ENG U5: Autoation, Robotics and Prograabl Logic Controllrs (PLCs) 28 UniCours Ltd. All Rights Rsrvd. Exa 2 Us to dsign and siulat a laddr diagra for a si syst whr any on of thr norally-opn switchs, whn prssd, will driv a otor. Pag 23 of 24