Cau Truc Va Nguyen Ly Hoat Dong Cua PLC S7-200

7/27/2019 Cau Truc Va Nguyen Ly Hoat Dong Cua PLC S7-200

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Gio trnh ng dng tin hc trong CTM

1

Mc lc

Ch-ng 1. Cu trc v nguyn l hot ng ca PLC ........................................................21.1. Khi nim v PLC ......................................................................................................... 2

1.1.1. Khi nim ............................................................................................................... 21.1.2. c im ................................................................................................................. 21.1.3. -u im................................................................................................................... 2

1.1.4. So snh vi h thng iu khin r-le .................................................................... 31.2. Cu trc phn cng ca PLC ...................................................................................... 5 1.2.1. Kt cu chung ca h thng PLC........................................................................... 51.2.2. Cu trc bn trong ca PLC................................................................................... 7

1.3. Hot ng ca PLC .................................................................................................... 141.3.1. Chu k hot ng.................................................................................................. 141.3.2. a ch ng vo v ng ra..................................................................................... 151.3.3. Cu trc b nh.................................................................................................... 161.3.4. Cc ph-ng php lp trnh.................................................................................... 18

1.4. Cc lnh bit logic ........................................................................................................ 20

1.4.1. Cc lnh bit logic tip im (contacts)................................................................. 201.4.2. Cc lnh bit logic xut (output)............................................................................ 221.4.3. Lnh bit logic ghi (set) v xo (reset).................................................................. 24

1.5. Cc lnh so snh d liu. ........................................................................................... 251.6. Lnh Timer .................................................................................................................. 25

1.6.1. nh ngha v phn loi........................................................................................ 251.6.2. Tnh cht ca Timer.............................................................................................. 261.6.3. C php khai bo s dng Timer......................................................................... 261.5.4. V d s dng Timer............................................................................................. 28

1.7. Lnh Counter .............................................................................................................. 311.7.1. Phn loi Counter................................................................................................. 311.7.2. C php khai bo s dng Counter...................................................................... 311.7.3. Th d s dng counter......................................................................................... 32

1.8. Cc lnh di chuyn d liu ......................................................................................... 331.9. Cc php tnh s hc ................................................................................................... 34

1.9.1. Khi nim v phn loi php tnh s hc............................................................. 341.9.2. Khai bo php tnh trong ch-ng trnh................................................................ 341.9.3. Th d v php tnh s hc................................................................................... 36

1.10. Lp trnh PLC .......................................................................................................... 371.10.1. Cu trc ch-ng trnh PLC................................................................................. 381.10.2. Cc b-c lp trnh............................................................................................... 38

1.10.3. Kt ni linh kin vo/ra (nhp/xut).................................................................. 401.10.4. V d lp trnh PLC............................................................................................ 41


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Ch-ng 1. Cu trc v nguyn l hot ng ca PLC

1.1. Khi nim v PLC

1.1.1. Khi nim

PLC xut hin ln u vo nm 1968 nhm thay th cc panel iu khin kiu r-le cacc h thng iu khin chu trnh. Tuy nhin t nm 1970 kh nng ca PLC ni bt,

-c b sung nhiu chc nng khc: chng khng ch thc hin cc chc nng iu khinn gin m cn gim st cc h thng sn xut phc tp. Ngy nay PLC c mt trongcc h thng x l tn hiu s v truyn thng tc cao. NEMA (National ElectricalManufacturing Association) nh ngha PLCl thit b in t s. Chng s dng ch-ngtrnh l-u b nh trong thc hin cc hm (lnh) c bit nh- logic, nh thi gian, m,s hc... iu khin cc loi thit b hay cc qu trnh khc nhau thng qua cc module

xut/nhp dng s hoc t-ng t". nh ngha ny cho thy PLC l mt thit b in t, thchin cc php tnh logic trn cc tn hiu vo (Inputs) xut ra (Output) cc tn hiu iukhin.

1.1.2. c im

Thit b iu khin logic lp trnh (PLC) l dng thit b iu khin c bitda trnb vi x l, s dng b nh lp trnh -c l-u tr cc lnh v thc hin cc chc nng,chng hn, php tnh logic, lp chui, nh gi, m, v thut ton iu khin my v ccqu trnh (Hnh 1.1). PLC-c thit k cho php cc k s-, khng yu cu kin thc cao vmy tnh v ngn ng my tnh, c th vn hnh d dng.

Hnh 1.1 S b iu khin logic lp trnh PLC

PLC khng -c thit k ch c cc nh lp trnh my tnh mi c th ci t hocthay i ch-ng trnh. V vy, cc nh thit k PLCphi lptrnh sn sao cho ch-ng trnhiu khin c th -c nhp bng cch s dng dng ngn ng n gin. Thut ng logic-c s dng v vic lp trnh ch yu lin quan n cc hot ng logicthc thi v chuynmch, v d, nu s kin Ahoc Bxy ra, ngmch C, nu s kin Av Bxy ra, ng

mch D... Cc thit b nhp, chng hn cc b cm bin, cc cng tc, v cc thit b xuttrong h thng -c iu khin, v d, cc ng c, cc van... -c ni kt vi PLC. Ng-ivn hnh nhp chui lnh (ch-ng trnh) vo b nh ca PLC. Thit b iu khin s gimst cc tn hiu vo v cc tn hiu ra theo ch-ng trnh ny v thc hin cc quy tc iukhin -c lp trnh.

1.1.3. -u im

Cc PLCc -u im chnhl c th s dng cng mt thit b iu khin c bn chonhiu h thng iu khin. sa i h thng iu khin v cc quy tc ang -c sdng, ng-i vn hnh ch cn nhp tp lnh khc; khng cn mc ni li dy. Nh , h

thng rt linh hot v hiu qu.Cc PLC t-ng t my tnh, nh-ng my tnh -c ti -u ha cho cc nhim v tnh

ton v hin th; cn PLC-c chuyn bit cho cc nhim v iu khin v mi tr-ng snxut cng nghip. V vy, cc PLC -c thit k:


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- chu -c rung ng, nhit, m v ting n.- Csn giao din cho cc thit b nhp v thit b xut. - D dng vi ngn ng lp trnh d hiu, ch yu gii quyt cc php ton logic

v chuyn mch.

1.1.4. So snh vi h thng iu khin r-le

Tr-c y, PLC c nhiu hn ch nh- gi thnh t, kh nng lp trnh hn ch v ccth tc lp trnh phc tp. V vy, chng ch -c s dng trn cc my cng c c bit(CNC) hay trn cc thit b phi thay i ch-ng trnh lm rlc trong qu trnh vn hnh.Tuy nhin do gi c khng ngng h, cng vi vic lun tng c-ng cc kh nng ca PLC,cho php PLCngy cng -c s dng rng ri hn v cho n nay th n l thit b iukhin ph bin. Cc cng dng ca PLC c rt nhiu li th cho c ng-i thit k v ng-is dng. Sau y l cc th mnh -c th hin ca PLC.

a) Phn phi nhanh chng.

Thit k theo module cho php PLC p ng mi yu cu iu khin. Biu khin vcc cu kin km theo -c ch to ng b, c th nng cp tc thi.

b) tin cy cao.

Cc linh kin in t c tui th phc v cao hn cc thit b in-c. Do , tui thca PLC-c nng ln v thi gian phc v -c ko di. Vic bo d-ng nh k th-ng lvn rt quan trng i vi cc b iu khin r-le, nh-ing b loi b i vi PLC.

c) D dng lp v sa i ch-ng trnh.

Nhng thay i khi bt u ch-ng trnh hoc tip theo c th d dng thc hin mkhng cn thay i mt s u dy no. Mi s thay i trong ch-ng trnh -c t ngl-u li.

Khi s dng b iu khin vo cc thit b khc nhau t v trnh t thc hin th ch-ng

trnh c th -c dng li bi s sao chp gin n, sau thay i v thm vo cc phnmi. Cc phn ch-ng trnh sn c c th -c s dng li m khng thay i. So vi iukhin dng k thut r-le, ton b thi gian lp rp c th gin i ng kbi ton b ccchc nng c th -c lp trnh tr-c hoc trong khi lp rp.

d) D dng xc nh cu hnh.

Nu bit s l-ng tn hiu u vo, u ra trong nhiu PLC, s l-u tr d liu -cthc hin t ng, lm cho s thit k mch in n gin hn.

e) Khng gian lp t nh gn.

Cc PLCyu cu t khng gian hn cc b iu khin r-le t-ng t. Trong nhiu

tr-ng hp khng gian lp my gim do loi b -c nhiu bng mch ring r. f) C kh nng ti to.

S dng PLCvo mt yu cu c th lm gimchi ph lao ng so vi iu khin r-lev b -c phn ln chi ph lp rp. V vy PLCkhng ch -c dng trn cc thit b thnghim m cn trn cc thit b tiu chun.

Hin nay, cc h thng iu khin bng PLC ang dn dn thay th cho cc h thngiu khin bng relay, contactor thng th-ng. Ta hy th so snh -u, khuyt im ca haih thng trn:

H thng iu khin thng th-ng:

Th kch do c qu nhiu dy dn v relay trn bn iu khin. Tn kh nhiu thi gian cho vic thit k, lp t . Tc hot ng chm.


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Cng sut tiu th ln. Mi ln mun thay i ch-ng trnh th phi lp t li tan b, tn nhiu thi gian. Kh bo qun v sa cha.

H thng iu khin bng PLC:

Nhng dy kt ni trong h thng gim -c 80% nn nh gn hn.

Cng sut tiu th t hn. S thay i cc ng vo, ra v iu khin h thng tr nn d dng hn nh phn

mm iu khin bng my tnh hay trn Console.

Tc hot ng ca h thng nhanh hn. Bo tr v sa cha d dng. bn v tin cy vn hnhcao. Gi thnh ca h thng gim khi s tip im tng. C thit b chng nhiu. Ngn ng lp trnh d hiu. D lp trnh v c th lp trnh trn my tnh, thch hp cho vic thc hin cc lnh

tun t ca n.

Cc modul ri cho php thay th hoc thmvo khi cn thit.Do nhng l do trn PLC th hin r -u im ca n so vi cc thit b iu khin

thng th-ng khc. PLC cn c kh nng thm vo hay thay i cc lnh tu theo yu cuca cng ngh. Khi ta ch cn thay i ch-ng trnh ca n, iu ny ni ln tnh nngiu khin kh linh ng ca PLC.


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1.2. Cu trc phn cng ca PLCH thng PLCthng dng c nm b phn c bn, gm b x l, b nh, b ngun,

giao din nhp/xut, v thit b lp trnh. Hnh 1.2 minh ha s khi c bn.

Hnh 1.2 Cu trc ca b iu khin logic lp trnh PLC in hnh.

Bx lcn gi l b vi x l trung tm (CPU), l linh kin cha b vi x l, bindch cc tn hiu nhp v thc hin cc hot ng iu khin theo ch-ng trnh -c l-utrong b nh ca CPU, truyn cc quyt nh d-i dng tn hiu hot ng n cc thit bxut.

Bngunc nhim v chuyn i in p ACthnh in p thp DC(5V) cn thitcho b vi x l v cc mch in trong cc module giao din nhp v xut.

Thit b lp trnh-cs dng nhp ch-ng trnh cn thit vo b nh ca b vix l. Ch-ng trnh -c vit trn thit b ny, sau -c chuyn n b nh ca PLC.

Bnh l ni l-u ch-ng trnh -c s dng cho cc hot ng iu khin, d-i skim tra ca b vi x l.

Cc cng nhp v xutl ni b x l nhn thng tin t cc thit b ngoi vi v truynthng tin n cc thit b bn ngoi. Tn hiu nhp c th t cc cng tc hnh trnh trnmy khoan t ng, hoc cc b cm bin, chng hn, cc t bo quang in trong c cum, cc b cm bin nhit , hoc cc b cm bin l-u l-ng... Cc thit b xut c thn cun dy ca b khi ng ng c, cc van in t (solenoid)... Cc cngnhp v xuts -c trnh by trong mc 2.2. Cc thit b nhp v xut c th -c phn loi theo kiutn hiu cung cp: ri rc, digital hoc analog (hnh 1.6).

1.2.1. Kt cu chung ca h thngPLC

C hai kiu kt cu thng dng i vi cc h thng PLC: kiu hp n, v kiumodule ni ghp. Kiu hp n (hnh 1.3a) th-ng -c s dng cho cc thit b iu khinlp trnh c nh v -c cung cp d-i dng nguyn chic hon chnh gm b ngun) b xl, b nh v cc thit b nhp/xut. Thng th-ng kiu PLCny c th c 40 ng nhp/xutv b nh c th l-u tr khong 300-1000 lnh .

Kiu module (hnh 1.3b) gm cc module ring cho b ngun, b x l... Chngth-ng -c lp trn cc rnh bn trong hp kim loi. Kiu ny c th -c s dng cho ccthit b iu khin lp trnh vi mi kch c, c nhiu b chc nng khc nhau -c gp vo

cc module ring bit, c th -c cm vo cm trn rnh (slot) chnh. S phi hp ccmodule cn thit ty theo cng dng c th do ng-i dng xc nh. V vy kiu ny khlinh hot, cho php m rng s l-ng u ni nhp/xut bng cch b sung cc modulenhp/xut hoc tng c-ng b nh bng cch tng thm cc n v nh.


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Cc ch-ng trnh -c -a vo b nh ca PLCbng thit b lp trnh, thit b nykhng ni kt c nh vi PLC, v c th chuyn t thit b iu khin ny n thit b iukhin khc m khng lm xo trn cc hot ng. PLCc th vn hnh m khng cn nikt vi thit b lp trnh, sau khi ch-ng trnh -c ti vo b nh ca PLC.

a) b)

Hnh 1.3Cu trc chung ca PLC

a) Kiu hp n, b) Kiu module ni ghp

Hnh 1.4. Cc b phn bn ngoi ca mt PLC

Cc thit b lp trnh c th l loi cm tay, bn, hoc my tnh. Cc h thng cmtay c bn phm nh v mn hnh tinh th lng . Cc thit b bn c th c b hin th vibn phm hon chnh v mn hnh hin th. Cc my tnh c nhn -c lp cu hnh nh- cctrm lm vic pht trin ch-ng trnh. Mt sPLCi hi my tnh phi c phn mmt-ng ng, s khc chi cn th mch truyn thng chuyn dng giao tip vi PLC. -uim chnh khi s dng my tnh l ch-ng trnh c th -c l-u trn a cng hoc amm v d dng thc hin cc bn sao. Nh-c im l vic lp trnh th-ng kh thc hin.Cc thit b giao tip lp trnh cm tay th-ng c b nh l-u gi ch-ng trnh trongkhi chuyn t v tr ny n v tr khc.

Ch-ng trnh ch -c chuyn vo b nh ca PLCkhi -c vit hon chnh trnthit b lp trnh.


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1.2.2. Cu trc bn trong ca PLC

Hnh 1.5 minh ha cu trc bn trong c bn ca PLC, gm b x l trung tm (CPU)cha b vi x l h thng, b nh, v mch nhp/xut CPUiu khin v x l mi hotng bn trong PLC: Bx l trung tm -c trang b ng h c tn s trong khong 1 n8 MHz. Tn s ny quyt nh tc vn hnh ca PLC, cung cp chun thi gian v ng b ha tt c cc thnh phn ca h thng. Thng tin trong PLC-c truyn d-i dng cctn hiu digital. Cc -ng dn bn trong truyn cc tn hiu digital d-c gi l cc bus. Vvt l, bus l b dy dn, truyn tn hiu in. Bus c th l cc vt dn trn bn mch inhoc cc dy in trong cp. CPUs dng bus d liu gi d liu gia cc b phn, busa ch gi a ch cc v tr truy cp d liu -c l-u tr v bus iu khin dn tn hiulin quan n cc hot ng iu khin ni b. Bus h thng -c s dng truyn thnggia cc cng v thit b nhp/xut.

Hnh 1.4 Cu trc bn trong ca PLC

-B x l trung tm - CPUCu hnh CPUty thuc vo b vi x l. Ni chung, CPU c:


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B tnh ton s hc v b logic (ALU) chu trch nhim x l d liu, thc hin ccphp ton s hc (cng, tr) v cc php ton logic AND, OR, NOT v EXCLUSIVE-OR.

Bnh, cn gi l cc thanh ghi, bn trong b vi x l, -c s dng l-u tr thngtin lin quan n s thc thi ch-ng trnh.

Biu khin-c s dng nh chun thi gian ca cc php ton.

--ng truyn -BUS

Busl cc -ng dn dng truyn thng bn trong PLC. Thng tin -c truyn theodng nh phn, theo nhm bit, mi bit l mt s nh phn 1 hoc 0, t-ng ng vi cc trngthi ON/OFF. Thut ng t my (WORD) -c s dng cho nhm bit to thnh thng tinno . V vy mt t my 8-bit c th l s nh phn 00100110. C 8-bit ny -c truynng thi theo -ng dn song song ca chng. H thng PLCc bn bus:

Bus d liu ti d liu trong qu trnh x l ca CPU. Bvi x l 8-bit c mt bus dliu ni c th thao tc cc s nh phn 8-bit, c th thc hin cc php ton gia cc s nhphn 8-bit v phn phi kt qu theo gi tr 8-bit.

Bus a ch -c s dng ti a chcc v tr trong b nh. Nh- vy, mi t my c

th d-c nh v trong b nh, mi v tr nh -c gn mt a ch duy nht. Mi v tr tmy -c gn mt a ch sao cho d liu -c l-u tr v tr nht nh, CPU c th choc ghi . Bus a ch mang thng tin cho bit a ch s -c truy cp. Nu bus a chgm 8 -ng s l-ng t my 8-bit, hoc s l-ng a ch phn bit l 28= 256. Vi bus ach 16 -ng s l-ng a ch kh dng l 65536.

Bus iu khin mang cc tn hiu -c CPUsdng iu khin; v d, thngbo cho cc thit b nh nhn d liu t thit b nhp hoc xut d liu, v ti cc tn hiuchun thi gian -c dng ng b ha cc hot ng.

Bus h thng -c dng truyn thng gia cc cng nhp/xut v thit b nhp/xut.

-BnhTrong h thng PLCc nhiu loi b nh:

Bnh ch c (ROM) cung cp dung l-ng l-u tr cho h iu hnh v d liu cnh -c CPUs dng.

Bnh truy cp ngu nhin (RAM) dnh cho ch-ng trnh ca ng-i dng.

Bnh truy cp ngu nhin (RAM) dnh cho d liu. y l ni l-u tr thng tin theotrng thi ca cc thit b nhp/xut cc gi tr ca ng h thi chun, cc b m v ccthit b ni vi khc. RAMd liu i khi -c xem l bng d liu hoc bng ghi. Mt phnca b nh ny, khi a ch, dnh cho cc a ch ng vo v ng ra, cng vi trng thi cacc ng vo v ng ra . Mt phn dnh cho d liu -c ci t tr-c, v mt phn khcdnh l-u tr cc gi tr ca b m, cc gi tr ca ng h thi chun ...

Bnh ch c c th xo v lp trnh -c (EPROM) l cc ROMc th -c lptrnh, sau ch-ng trnh ny -c th-ng tr trong ROM.

Ng-i dng c th thay i ch-ng trnh v d liu trong RAM. Tt c cc PLCu cmt l-ng RAM l-u ch-ng trnh do ng-i dng ci t v d liu ch-ng trnh. Tuynhin, trnh mt mt ch-ng trnh khi ngun cng sut b ngt, PLCs dng c quy duy tr ni dung RAMtrong mt thi gian. Sau khi -c ci t vo RAM, ch-ng trnh cth -c ti vo vi mch ca b nh EPROM, th-ng l module c kha i vi PLC, do ch-ng trnh tr thnh vnh cu. Ngoi ra cn c cc b m tm thi, l-u tr cc knh

nhp/xut.Dung l-ng l-u tr ca b nh -c xc nh bng s l-ng t my nh phn c th

l-u tr -c. Nh- vy, nu dung l-ng b nh l 256 t my, b nh c th l-u tr 256x8=2048 bit, nu s dng cc t my 8-bit, v 256x16 = 4096 bit, nu cc t my -c s


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dng l 16 bit. Kch c b nh th-ng -c chuyn bit theo s l-ng v tr l-u tr kh dngvi 1K biu din s nh phn 210= 1024. Cc nh sn xut cung cp vi mch b nh vi ccv tr l-u tr theo nhm 1, 4, v 8 bit. B nh 4Kx1 c 4x1xl024 bit v tr. Bnh 4Kx8 c4x8xl024 bit v tr. Thut ng byte -c s dng cho t my c di 8 bit.V vy, b nh4Kx8 c th l-u tr 4096 byte. Vi bus a ch 16-bit, bn c th c 216a ch khc nhau,v vi cc t 8-bit -c l-u tr mi a ch, bn c th c 216x 8 a ch l-u tr, v sdng b nh c dung l-ng 216x 8/210= 64Kx8, bn c th c cu hnh gm bn vi mchnh 16Kx8.

-Mch(modun)giao din.Mch giao din -c dng lin kt cc thit b ngoi vi, nh- mn hnh, thit b lp

trnh hoc cc linh kin m rng khc ca PLC. Ngoi ra m rng kh nng ca PLC, ccnh ch to cn cung cp cc module logic thc hin cc chc nng c bit. Vic ci tcc module ny vo ht sc d dng bng cch ghp chng vo cc rnh (slots) c sn trnPLC c s.

- Cc mch nhp/xut(vo/ra).Tn hiu nhp t cc b cm bin, cng tchnh trnh... v cc tn hiu xut n cc

thit b dn ng, c cu chp hnh... c th l:- Analog, tn hiu c kch c lin quan vi i l-ng ang -c cm bin.- Ri rc, v bn cht ch l tn hiu ng-ngt.- Digital, l chui xung dng m s.

Cc thit b cung cp tn hiu ri rc hoc digital l cc thit b c tn hiu ON/OFF(hnh 1.5).

a) Tn hiu ri rc b) Tn hiu digital c) Tn hiu analog

Hnh 1.5. Cc loi tn hiu

Cng tc l thit b cung cp tn hiu ri rc, c hoc khng c inp. V c bn, ccthit b digital c th -c xem l cc thit b ri rc, vi chui cc tn hiu ON/OFF. Ccthit b analog cung cp cc tn hiu c ln t l vi gi tr ca bin ang -c gim st.V d, b cm bin nhit c th cung cp in p t l vi nhit .

Tuy nhin, CPUcn c ng vo cho cc tn hiu digital c ln xc nh, th-ng t 0 n 5V. Tn hiu ra t CPUl digital, th-ng t 0 n 5V. V vy, cn phi x l cc tnhiu vo v tn hiu ra chng c dng theo yu cu. Mch nhp/xut ca cc PLC -cthit k sao cho di tn hiu vo c th -c i thnh cc tn hiu digital 5V, v di tn hiura l kh dng truyn ng cc thit b ngoi vi. Tnh nng ny cho php x l di tnhiu vo v tn hiu ra cc PLCddng s dng.

Ni chung, di tn hiu vo trn module nhp -c chn la bng cc cng tc DIP(Dual-In-Line Package). Cc cng tc ny -c b tr mt sau module. Chng ch c haitrng thi ng hoc ngt, v -c s dng ci t cc tham s cho module. Cc cng tcny cng -c s dng xc lp a ch ca cc module.

D-i y chng ta s xem xt mt s mch xut v nhp c bn -c s dng trongPLC. i vi cc thit b kiu module, chng -c gn ln cc th mch, c th -c cmvo cc rnh. V vy, bn c th thay i cc c tnh nhp/xut ca PLCbng cch thay i


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th mch. PLC dng hp n c cc thit b nhp/xut -c nh sn xut gn cng bntrong.

Hnh 1.6 v 1.7 minh ha cc mch nhp c bn i vi cc tn hiu vo ri rc, digitalDC v AC. Cc b cch in quang hc -c s dng bo v. i vi th mch dng chotn hiu vo dng AC, mng cu chnh l-u -c s dng chnh l-u dng AC sao chotn.hiu DC c th cung cp tn hiu m b cch in quang hc s dng to ra cc tn

hiu nhp vo CPU

ca PLC.

Hnh 1.6.

Hnh 1.7. Mch nhp (vo)

Tn hiu mt chiu DC (trn); b) Tn hiu xoay chiu AC (d-i)

Cc tn hiu analog c th -c nhp vo PLC, nu mch nhp ca PLCc kh nngchuyn tn hiu thnh tn hiu digital qua b chuyn i analog-digital. i vi h thng-c lp theo rnh, vic nhp tn hiu analog c th thc hin bng cch lp bn mch cng vo analog thch hp trn rnh ng vo. Do , khng cn bn mch con analog chotng ng vo analog, thay vo c th s dng chuyn mch in t(hnh 1.8). B phnny gm nhiu ng vo analog i vi bn mch con v s dng cc cng tc in t lnl-t chn la tng tn hiu nhp. Cc bn mch con thng dng c 4, 8, hoc 16 ng voanalog.


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Tn hiu vo Analog (V) Tn hiu ra Digital0.00 0000 00000,04 0000 00010,08 0000 00100,12 0000 00110,16 0000 01000,20 0000 0101

0,24 0000 01100,28 0000 01110,32 0000 1000.... ....

Hnh 1.11. Cc mch xut c bn ca PLC

a) Mch xut kiu transistor, b) Mch xut kiu triac; c) Mch xut kiu r-le.

minh ha cho vn trn, c th xt cp nhit in -c dng lm b cm bin choPLCv cung cptn hiu ra 0,5 mV/0C. Cn tm chnh xc bo m PLCkch hot thitb xut khi cp nhit in ni vi ng vo analog trong khong 0- 10V DC, s dng ADC10-bit. Vi b chuyn i 10-bit s c 210= 1024 bc trn di tn hiu vo analog 0 n10V. Vvy, s thay i l bc t-ng ng 10/1023 V (0,01V = 10 mV). T , phn giichnh xc PLCphn bit tn hiu vo t cp nhit in l 5 mV t-ng ng 100C.

Cc mch xut c th l r-le, transistor hoc triac. Hnh 1.11a minh ha dng cc cbn ca mch xut kiu r-le, hnh 1.11b trnh by cc mch xut kiu transistor v hnh

1.11c minh ha mch xut kiu triac.Tn hiu ra analog c nhu cu rt ln v c th -c cung cp bng b chuyn i

digital-analog (DAC) knh xut. Tn hiu vo b chuyn i ny l chui bit, vi mi bit


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trn mt -ng song song. Hnh 1.12 trnh by chc nng c bn ca chuyn i ny. Bittrn -ng 0cung cp xung tn hiu ra c c-ng nht nh. Bit trn -ng 1 cung cpxung tn hiu ra c c-ng gp i xung trn -ng 0. Bit trn -ng 2 cung cp xung tnhiu ra c c-ng gp i xung trn -ng 1. Bit trn -ng 3 cung cp xung tn hiu rac c-ng gp i xung trn -ng 2... Tt c cc tn hiu ra ny kt hp vi nhau tothnh dng analog ca tn hiu vo digital. Khi tn hiu vo digital thay i, tn hiu raanalog thay i theo bc, s thay i in p tn hiu ra bng cc thay i in p lin ktvi mi bit. V d, nu s dng b chuyn i 8-bit, tn hiu ra to thnh cc gi tr in pgm 28= 256 bc analog. Gi s di tn hiu ra -c xc lp n 10V DC, mt bit cung cps thay i 10/255 V (0,04 V). Nh- vy:

Tn hiu vo digital Tn hiu ra Analog (V)0000 0000 0.000000 0001 0,040000 0010 0,08 + 0,00 = 0,080000 0011 0,08 + 0,04 = 0,120000 0100 0,160000 0101 0,16 + 0,00 + 0,04 = 0,20

0000 0110 0,16 + 0,08 = 0,240000 0111 0,16 + 0,08 + 0,04 = 0,280000 1000 0,32

.... ....Cc module xut analog th-ng -c cung cp theo s tn hiu ra, v d, 4 n 20 mA,

0n +5V DC, 0 n +10V DC, v tn hiu ra thch hp -c chn bng cc cng tc DIPtrn module. Thng th-ng, module c cc ng ra chia thnh hai dng, th nht, mi ng raca module c ngun in p chung, th hai, cc ng ra c ngun in p ring. Hnh 1.13trnh by cc nguyn l c bn ca hai dng ng ra ny.

Hnh 1.12. Chc nng ca DAC

Hnh 1.13. Cc dng ng ra.

a) Ngun chung, b) Ngun ring


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1.3. Hot ng ca PLC

1.3.1. Chu k hot ng

Cc ch-ng trnh PLC biu din dy cc lnh lp trnh tun theo mt c php tu thucvo ngn ng lp trnh (mi mt b iu khin c mt ngn ng lp trnh ring). Thit bPLC thc hin ch-ng trnh bt u t lnh lp trnh u tin v kt thc lnh lp trnhcui trong mt dng. Mt vng qut nh- vy -c gi l mt chu k.

Mt vng qut bt u bng vic c trng thi ca u vo, sau thc hin ch-ngtrnh v kt thc bng vic thay i trng thi ca u ra. Tr-c khi bt u vng qut tiptheo, b iu khin thc hin cc nhim v t kim tra sa liv nhim v truyn thng.Hnh 1.14 minh ha hot ng ny. Chai ph-ng php c th -c s dng cho cc hotng x l tn hiu nhp/xut.

Hnh 1.14. Hot ng ca PLC

Cp nht lin tcTheo ph-ng php ny, CPUqut cc knh nhp khi chng xut hin theo cc lnh

ca ch-ng trnh. Mi im nhp -c kim tra ring r v tc ng ca chng ln ch-ngtrnh s -c xc nh. S yu cu tng im nhp theo mi lnh ch-ng trnh s tn thigian. Nhiu knh nhp c th phi -c qut tr-c khi ch-ng trnh c ch th thc thihot ng c th v tn hiu ra xut hin. Cc tn hiu ra duy tr trng thi ca chng, bkha cho n khi c s cp nht k tip. Tp lnh ny bao gm:

- Tm np v gii m lnh ch-ng trnh th nht.- Qut cc ng vo t-ng ng.- Tm np v gii m lnh ch-ng trnh th hai.- Qut cc ng vo t-ng ng... i vi cc lnh cn li.- Cp nht cc ng ra.- Lp li ton b tp lnh trn.

Sao chp khi tn hiu nhp/xut.Do ph-ng php cp nht lin tc cn c thi gian kim tra ln l-t tng im nhp,

thi gian cn thit kim tra vi trm im nhp/xut c th ng k. thc thi ch-ngtrnh nhanh hn, mt vng c bit ca RAM-c s dng lm b l-u tr m gia logiciu khin v b nhp/xut. Mi b nhp/xut u c a ch trong vng nh ny. Khi btu mi chu k ch-ng trnh CPUqut tt c cc b nhp v sao chp trng thi ca chngvo cc a ch ca b nhp/xut trong RAM. Khi ch-ng trnh -c thc thi, CPU c d


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liu -c l-u tr trong RAM, theo yu cu, v thc hin cc php ton logic. Tn hiu xut-c l-u tr trong phn RAMdnh ring cho nhp/xut. Cui mi chu k ch-ng trnh, ttc cc tn hiu xut trong RAMu -c chuyn n cc knh xut t-ng ng. Cc tn hiuxut vn duy tr trng thi ca chng cho n chu k cp nht k tip. Tp lnh ny baogm:

- Qut tt c cc n v nhp v sao chp vo RAM- Tm kim, gii m, v thc thi tt c cc lnh ca ch-ng trnh theo th t, saochp cc ch th xut vo RAM.- Cp nht tt c cc ch th xut.- Lp li tp lnh trn.

Mc d thi gian cn thit hon tt chu k qut cc ng vo v cp nht cc ng ratheo cc lnh ch-ng trnh t-ng i ngn, nh-ng khng phi tc thi. Ngha l, cc ng vokhng -c theo di lin tc, cc mu trng thi ca chng -c ly nh k. Thi gian cachu k thng th-ng khong 10 n 50 ms, ngha l cc ng vo v cc ng ra -c cp nhtmi 10 n 50 ms, nh- vy, s p ng ca h thng c th b tr. iu ny cng c ngha l

nu c chu k nhp rt ngn xy ra

thi im khng thch hp, chu k c th b b st.Tm li, chu k nhp bt k phi xut hin trong thi gian di hn thi gian chu k caPLC. Cc module c bit c th hu ch trong cc tr-ng hp nu trn.

Hy xt PLCc thi gian chu k 40 ms. Tn s cc i ca cc xung digital l baonhiu c th -c pht hin? Nu mi 40 ms c mt xung xut hin, tn s cc i s l:1/0,04 = 25 Hz.

Th d v cp nht gi tr cc cng nhp (input) v xut (output) vo vng nh(hnh1.15):

Hnh 1.15. Hot ng cp nht cng vo/ra

1.3.2. a ch ng vo v ng ra

PLCc kh nng nhn bit tng ng vo v ng ra bng cch gn a ch cho chng.Vi PLCnh, a ch l ch s c tip u ng cho bit l ng vo hoc ng ra. i viPLCMitsubishi. cc ng vo c a ch dng X400, X401, X402... v cc ng ra c a ch

dng Y430, Y431, Y482... Nh- vy X biu th ng vo v Y l ng ra. Hng Toshiba cngs dng h thng a ch t-ng t.


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Cc PLCln c nhiu rnh cho cc knh nhp v knh xut, cc rnh ny -c nhs. Vi Allen Bradley PLC-5, rnh cha b x l -c gn s 0v a ch cc rnh khc-c nh s 1, 2, 3... ty theo cch ci t cc cng tc. Mi rnh c th c nhiu modulev mi module lin quan vi nhiu ng vo/ra. Hnh 1.16 minh ha dng a ch ny. V d,ng vo c a ch I:012/03. a ch ny cho bit (I) l ng vo, rnh 01, module 2 vthit b u cui 03.

Hnh 1.16. Cch ghi a ch trn Allen Bradley PLC-5

Vi Siemens SIMATIC S7, cc ng vo v cc ng ra -c sp xp theo nhm 8. Mi

nhm 8 -c gi l byte v mi tn hiu vo hoc ra c 8 bit. Cc ng vo v ra c a ch-c biu din bng cc s byte v bite, to thnh s module, tip theo l s thit b ucui, du chm (.) phn chia hai s ny. Hnh 1.17 trnh by h thng a ch ny. V d I0.1l ng vo bit 1 trong byte 0, Q2.0 l ng ra bit 0 trong byte 2.

Hnh 1.17. Cch ghi a ch trn Siemens SISMATIC S7

PLC GEM-80 biu din a ch cc ng vo/ra bng s module v s thit b u cuitrong module . Ch ci A -c dng biu th cc ng vo, v ch ci B biu th ccng ra. V d, A3.02 l ng vo thit b u cui 02 trong module 3, B5.12 l ng ra thitb u cui 12 trong module 5.

Vi Sprecher+Schuh SESTEP, cc ng vo -c biu th bng chci X v cc ng ra

l Y v -c nh s th t. V tr ca module khng nh h-ng n cch ghi a ch. V d,X002 l ng vo v Y003 l ng ra.

Ngoi vic s dng a ch nhn bit cc ng vo v cc ng ra, PLCcn s dngcc h thng a ch ca chng nhn bit cc thit b ni do phn mm to ra, chng hnnh- cc r-le ni, cc ng h tnh gi v cc b m.

1.3.3. Cu trc b nh

PLC chia b nh th nh bn vng nh, c t duy tr d liu trong thi gian nht nhkhi mt ngun. N c tnh nng ng cao, c/ghi -c trong to n vng tr vng SM(Special Memory) ch c.

-Vng nh ch-ng trnh:l min b nh dng l-u gi lnh ch-ng trnh. Vng n ythuc kiu Non- volatile c/ghi -c.


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- Vng nh tham s: l min l-u gi cc tham s nh-: t kha, a ch trm l-uch-ng trnh Cng ging nh- vng ch-ng trnh vng n y thuc kiu Non - volatilec/ghi -c.

-Vng nh d liu:-c s dng ct d liu ch- ng trnh bao gm kt qu phptnh, hng s -c nh ngha trong ch-ng trnh, b m truyn thng Mt phn ca vngnh n y (200 byte u tin i vi CPU222, 1Kbyte u tin i vi CPU214) thuc kiu

Non- volatile c ghi/-c.

Vng d liu li -c chia ra vi nhng min nh nh c cc cng dng khc nhaunh-:


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V: Variable Memory(Vng nh bin).

I: Input Image Register (Vng m cng v o).

O: Output Image Register (Vng m cng ra).

M: Interal Memory Bits (Vng nh ni).

SM: Special Memory Bits (Vng nh c bit).

Vng nh d liu l vng nh ng. N c th truy nhp theo tng bit, byte, t n, tkp -c s dng lm min l-u tr d liu cho cc thut ton, cc hm truyn thng, lpbng, hm dch chuyn, xoay vng thanh ghi, con tr a ch

Cc ph-ng php truy nhp:

Truy nhp theo Bit:Tn mim + a ch byte +.+ a ch bit.

V d: V150.4 - Ch bit th 4 ca byte 150 thuc min nh V.

Truy nhp theo Byte:Tn mim + B + a ch ca byte.

V d: VB50 - Ch byte th 50 thuc min V.

Truy nhp theo t n:Tn min + W + a ch byte cao ca t trong min.

V d: VW150 - Ch t n gm 2 byte 150 v 151 thuc min V. Trong byte 150ng vai tr l byte cao, byte 151 ng vai tr l byte thp.

Truy nhp theo t kp:Tn min + D + a ch byte cao ca t kp trong min

V d: VD150 - Ch t kp gm 4 byte 150, 151, 152 v 153 thuc min V. Trong byte 150 ng vai tr l byte cao, byte 153 ng vai tr l byte thp.

-Vng i t-ng:-c s dng l-u tr d liu cho cc i t-ng lp trnh nh- ccgi tr tc thi, gi tr t tr-c ca b m hay timer. D liu kiu i t-ng gm thanh ghica timer, b m, cc b m c tc cao, b m v o/ra t-ng t v cc thanh ghiAccumulator (AC).

M t vng nh d liu v vng nh i t-ng th hin trong bng trn:1.3.4. Cc ph-ng php lp trnh.

Cba ph-ng php lp trnh PLCc bn: ph-ng php hnh thang (Ladder Logic - vittt l LAD) v ph-ng php lit k lnh (Statement List - vit tt l STL) v ph-ng php s khi hm (Function block diagram - FBD).Th d v 3 nhm thnh t lp trnh c bnca PLC th hin trn hnh 1.18.

LADl ngn ng lp trnh bng ho. Nhng phn t c bn dng trong LAD t-ngng vi cc phn t ca bng iu khin r-le. Trong ch-ng trnh dng LAD cc phn tc bn dng biu din cc lnh logic nh- sau:

- Tip im (contacts):l biu t-ng m t bitlogic dng tip im ca r-le. Cc tipim cth l th-ng m hoc th-ng ng.

- Cun dy (coil): l biu t-ng ---( )--- m t bit logic dng r-le -c mc theochiu dng in -c cp cho r-le.

- Hp (box): l biu t-ng m t cc chc nng khc nhau. Cc chc nng ny t-cthc hin khi c dng in chy n hp. Cc chc nng th-ng -c biu din bng hp lcc b thi gian (timer), b m (counter) v cc hm ton hc. Cun dy v cc hp phi-c mc ng chiu dng in.


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Hnh 1.18. Th d v cc phn t lp trnh c bn

LAD l ngn ng lp trnh ho. Mng LAD bao gm cc-ng ni cc phn tthnh mt mch hon thin, i t -ng ngun bn tri sang -ng ngun bn phi. -ngngun bn tri l dy nng, -ng ngun bn phi l dy trung ho hay l -ng tr v nicp ngun. Dng in chy t bn tri qua cc tip im ng, cc cun dy hoc cc hpv tr v bn phi ngun. Kiu lp trnh ny thun tin cho ng-i lp trnh quen vi s nguyn l mch iu khin kiu r-le.

a) b)

Hnh 1.19. Cc ph-ng php lp trnh PLC

a) Lp trnh theo LAD; b) Lp trnh theo FBD


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Ph-ng php lit k lnh STLl ph-ng php th hin ch-ng trnh d-i dng mt tphp danh sch cc cu lnh. Mi cu lnh trong ch-ng trnh, k c cc lnh hnh thc ubiu din mt chc nng ca PLC. Ph-ng php ny th hin cu lnh ging nh- ngn ngASSEMBLER hoc ngn ng lp trnh vi iu khin.Th d lp trnh theo STL th hin nh-sau:

S khi hml ngn ng lp trnh ho. Ngn ng ny cho php ngi lp trnhxy dng cc qui trnh iu khin phc tp bng cch ly cc hm t thvin FBD v vitchng vo mt din tch ho. Mt khi hm l gc biu din quan h hay hm gia ccbin u vo v u ra.

Ta c th xy dng hm hon chnh thao tc bi chng trnh FBD vi cc s khica cc hm c s t th vin FBD . M i khi hm c s c s l ng u vo/ra c nhtrn cc im ni. u vo c ni vo mt bn tri ca khi v u ra mt bn phi. Hmc s thc hin cc hm n gin gia cc u vo v u ra ca n. Kt qu ca hm logcc chuyn n u ra. Tn ca khi c k hiu bng cc k t la tinh.

S khi hm logic l mt ngn ng khiu, trong cc t hp khc nhau ca ccbin l gc c biu din bi cc k hiu logic tiu chun ho. T ng t nh s thang, lp trnh c trong ngn ngny ta cn phi c m n hnh hin th s .

1.4. Cc lnh bit logic

1.4.1. Cc lnh bit logic tip im (contacts)

Tip im tiu chun ca PLC gm cc loi sau: th-ng m (Normally Open-NO),th-ng ng (Normally Closed-NC), th-ng m tc th (Normally Open Immediate-NOI),th-ng ng tc th (Normally Closed Immediate NCI), NOT, Positive and Negative

Transition(hnh1.20).


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Hnh 1.20. Cc lnh bit logic tip im ca PLC S7200 (Siemence)

Th d s dng lnh bit logic tip im:

Th d 1:

Th d 2:


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1.4.2. Cc lnh bit logic xut (output)

Th d s dng bit logic output:


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1.4.3. Lnh bit logic ghi (set) v xo (reset)

Th d s dng lnh bit logic output, set v reset:


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C TON - TONR cng bt u to thi gian tr tn hiu k t thi im c s-n ln tn hiu u v o, tc l khi tn hiu u v o chuyn trng thi logic t 0 ln 1, -c gi l thi im Timer -c kch v khng tnh khong thi gian khi u v o c gi tr logic 0v o thi gian tr tn hiu -c t tr-c.

Timer kiu TOF bt u m li thi gian khi c s-n xung ca tn hiu u vo, tcl khi tn hiu u vo chuyn t trng thi logic t 1 v 0 (t ON sang OFF). Khi gi tr tc

thi ca Timer bng 0, T_bit ca n chuyn trng thi. Khi u v o c gi tr logic bng 0, TON t ng Reset cn TONR th khng.

Timer TON dng to thi gian tr trong mt khong thi gian (min ln thng), cnvi TONR thi gian tr s -c to ra trong nhiu khong thi gian khc nhau.

C TON v TONR gm ba loi vi ba phn gii khc nhau l 1ms, 10ms,100ms.Thi giantr to ra l tch ca phn gii ca b Timer -cchn v gi tr t tr-c choTimer(xem bng d-i).

Chus : S liu trong bng l ca PLC S7 200 ca Siemence

1.6.2. Tnh cht ca Timer

+) Cc b Timer -c iu khin bi mt cng v o v gi tr m tc thi. Gitr m tc thi ca Timer -c nh trong thanh ghi 2 byte l (T_word) ca Timer,

xc nh khong thi gian tr k t khi Timer kch. Gi tr t tr-c ca Timer l PT.

Gi tr m tc thi ca thanh ghi T_word th-ng xuyn -c so snh vi gi tr ttr-c ca Timer.

+) Mi b Timer ngo i thanh ghi 2 byte T_word l-u gi tr m tc thi, cn c mtbit k hiu T_bit ch th trng thi logic u ra. Gi tr logic ca bit n y ph thuc v o ktqu so snh gia gi tr m tc thi v t tr-c.

+) Trong khong thi gian tn hiu u v o c gi tr logic 1, gi tr m tc thi trong

T_word lun cp nhp v thay i tng dn cho n khi n t gi tr cc i. Khi gi trm tc thi (T_word) ln hn hay bng (>=) gi tr t tr-c (PT) th T_bit c gi tr logic1.

1.6.3. C php khai bo s dng Timer.

a) Trong LAD


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Mt Timer ang lm vic c th -c-av trng thi khi ng ban u. Cngvic-amt Timer v trng thi ban u gi l Reset Timer .

Khi Reset mt b Timer, T_word v T_bit ca n ng thi -cxo v c gi trbng 0, nn gi tr m tc thi t v 0 v tn hiu u ta cng c trng thi logicbng 0.C th Reset bt c b Timer n o ca S7-200 bng lnh Reset. Chng t R choT_bit camt Timer. Timer s -c-av trng thi ban u v c hai ph-ng php Reset mt

Timer kiu TON l xo tn hiu u v o hoc dng R.- Cp nhp Timer c phn gii 1ms cho php PLC cp nhp v thay i gi trmtc thi T_word mi 1ms mt ln. Timer c phn gii thp n y c kh nngiu khinchnh xc mt thao tc vic cp nhp T_word ho n to n t ng. B Timer1ms khng phthuc v o vng qut ca b iu khin v b ch-ng trnh ang. Gi trm tc thi T_bitca b Timer n y c th -ccp nhp bt c thi im n o trongvng qut v cp nhpnhiu ln trong mt vng qut nu thi gian vng qut ln hn1ms.

- Thc hin lnh Reset vi mt Timer c phn gii 1ms ang trng thilm victc thi l -aTimer v trng thi ban u, gi tr m tc thi ca Timer-c v 0 v T-bit nhn gi tr logic bng 0.

- Cp nhp Timer c phn gii 10ms: khi -ckch vic cp nhpT_word v T_bit thay i gi tr m tc thi v trng thi logic u ra ca mtTimer n y khngph thuc v o ch-ng trnh v cng ho n to n t ng, mi vngqut mt ln v ti uvng qut. Thc hin lnh Reset vi mt Timer ang trngthi lm vic l -aTimer vban u v xo T_word, T_bit ca Timer.

Do vic cp nhp T_word ca Timer ch -cthc hin t ng mi vng qutmt lnnn thi im thay i gi tr m tc thi v logic T_bit ca Timer c th b tri trongkhong 10ms.

- Cp nhp Timer c phn gii 100ms: a phn cc b Timer ca S7-200 l c

phn gii 100ms v -ctnh ti u vng qut v thi gian tnh s l khongthi gianu vng qut tr-c .

Vic cp nhp thay i gi tr m tc thi ca Timer ch -ctin h nh ngay tithi im c lnh khai bo cho Timer trong ch-ng trnh. Nn qu trnh cpnht gi tr mtc thi khng phi l qu trnh t ng v khng nht thit phi thchin mt ln trongmi vng qut ngay c khi Timer -ckch. Trong tr-nghplnh Timer 100ms -ckhai bo nhiu ln trong mt vng qut th xy ra hin t-ng gi tr l-utr b cng nhiu lnvi gi tr m tc thi, nn s dng lnh khai boTimer 100ms chnh xc mt ln trongmt vng qut.

Hiu qu cp nht gitr tc thi Timer 1ms, 10ms, 100ms do phn gii khc nhau-c thc hin ti cc thi im khc nhau ph thuc v o vic s dng cc Timer .

1.5.4. V d s dng Timer

a)Kiu TimerTON:


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Khong thi gian tr t tr-c: l = 10* 100 = 1000ms = 1s.

b) KiuTimer TOF:

Khong thi gian tr t tr-c l:100*10 = 1000ms = 1s.

c) Kiu Timer TONR:


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B m CTUD cng -c -a v trng thi khi pht ban u bng hai cch:

+ Khi u v o logic ca chn xo k hiu R (Reset) trong LAD hoc bit th nht cangn xp trong STL c gi tr logic l 1.

+ Bng lnh Reset vi C-bit ca b m.

CTUD c gi tr m tc thi bng gi tr ang m v l-u trong thanh ghi 2byteC_word. Gi tr m tc thi lun so snh vi gi tr t tr-c PV. Nu C_word ln hn

hoc bng PV th C_bit c gi tr logic bng 1 ng-c li th C_bit bng 0. V d:

Th d 1: S dng b m CTUD trong LAD v STL:

Th d 2:

1.7.3. Th d s dng counterVit ch-ng trnh iu khin mt n theo chu trnh iu khin sau: Khi nhnStart,

n sng 5s, sau n tt 5s v lp li cho n khi 5 ln th t tt m khngphi nhnStop.


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Bi lm:

t bin hnh thc:Start: I0.0 (NO), Stop: I0.1 (NC), n: Q0.0

1.8. Cc lnh di chuyn d liuCc lnh di chuyn d liu tun th kh nng truy cp a ch vng nh ca PLC. C

cc dng di chuyn d liu sau y:

- Di chuyn d liukiubyte(8 bit).- Di chuyn d liu kiu word(16 bit).- Di chuyn d liu kiu double word(32 bit).- Di chuyn d liu kiu real(32 bit).

Trong mt s tr-ng hp, ng-i lp trnh s dng lnh di chuyn d liu d liu chotr-c vo vng nh no tin l-u gi v s dng.

Lnh x l d liu th-ng gm lnh x l - d liu, a ch ngun (S), ni ly d liu;v a ch ch (D), ni chuyn d liu n. Hnh 1.21 minh ha dng lnh ph bincahng siemence.

Hnh 1.21. Khai bo lnh di chuyn d liu

Sau y l v d v cc loi lnh x l d liu -c dng vi PLC.

Lnh -c s dng ph bin di chuyn d liu l MOV. Lnh ny sao chp gi tr t

a ch ny sang a ch khc. Hnh 1.22 minh ha hng Siemens di chuyn d liu nh- hailnh ring bit, ti d liu t ngun vo b tch ly, ri chuyn d liu t b tch ly nch.


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Cc chuyn giao d liu c th di chuyn gi tr ci t tr-c n ng h dnh gihoc b m, thi gian hoc gi tr em n thanh ghi no l-u tr, d liu t ng von thanh ghi hoc t thanh ghin ng ra. Hnh 1.22 minh ha qu trnh di chuyn khi dliu a ch VB20 n a ch VB100 khi bt ng vo I2.1 chuyn t 0 sang 1. y cngmt lc di chuyn mt dy 4 khi d liu l-u tr trong 4 byte: VB20, VB21, VB22, VB23n dy 4 byte: V100, VB101, VB102, V103.

Hnh 1.22. Khai bo lnh di chuyn d liu

1.9. Cc php tnh s hc

1.9.1. Khi nim v phn loi php tnh s hc

Mt s PLC-c trang b ch thc hin cc php ton s hc cng v tr, mt skhc c th thc hin bn php ton c bn cng, tr, nhn v chia. Cc PLCc bit c ththc hin cc php ton s hc v cc hm, chng hn hm m. Cc php ton cng v tr-c s dng thay i gi tr d liu -c gi trong cc vng nh (thanh ghi) d liu. Vd, iu chnh tr s tn hiu vo ca b cm bin hoc c th thu -c gi tr no bng cch tr hai gi tr ca b cm bin hoc thay i cc gi tr -c xc lp tr-c ca

ng h nh gi v b m. Php nhn c th -c s dng tng tn hiu vo ln nhiuln tr-c khi cng hoc tr vi tn hiu khc.

Cc PLC-c lp trnh thc hin cc php tnh xc nh, sau ghi kt qu vo ach ch theo yu cu. Khi lnh tnh ton trn mn hnh lp trnh, tr-c tin cn nhp chn, ri n biu thc ton hc. Hnh 1.25 minh ha cc dng lnh tnh ton s hc sau:cng (ADD), tr (SUB), nhn (MUL) v chia (DIV). Cc php tnh thc hin vi cc loi dliu sau: s nguyn 16 bit - Integer (I), s nguyn 32 bit - (DI) v s thc 32 bit (R).

Mt s PLC c th thc hin php tnh khai cn bc haiSQRT ca s thc 32 bit, ktqu cho s thc 32 bit. C php nh- sau:

1.9.2. Khai bo php tnh trong ch-ng trnh

a) Php cng v php tr s nguyn 16 bit


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b) Php cng v tr s nguyn 32 bit

c) Php nhn v chia s nguyn 16 bit


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d) Php nhn v chia s nguyn 32 bit

1.9.3. Th d v php tnh s hc

a) Vi d liu l s nguyn 16 bit - integer(hnh 1.26):

b) Vi s nguyn 16 bit cho kt qu 32 bit


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Hnh 1.26. Th d v cc php ton s hc

1.10.


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1.10 Lp trnh PLCS khc nhau ch yu gia PLC v cc b iu khin dy cng (iu khin bn dn

hoc r-le) l k thut -a ch-ng trnh iu khin vo b iu khin. Trong iu khin dycng, trnh t lm vic (hay ch-ng trnh iu khin), ph thuc vo cc tip im, chuynmch... v ph-ng phpp ni chng vi nhau. Ng-c li, ch-ng trnh iu khin cho mtPLC thc hin thng qua bng lp trnh, sau chng -c l-u tr trong b nh in t.

Phn ny trnh by ph-ng php thit k ch-ng trnh v xem xt mt s v d minh ha .1.10.1. Cu trc ch-ng trnh PLC

Cu trc ca mt ch-ng trnh PLCni chung bao gm ch-ng trnh chnh v sau lcc ch-ng trnh con v ch-ng trnh x l ngt.

Ch-ng trnh chnh -c vit tr-c.

Ch-ng trnh conl mt b phn ca ch-ng trnh v -c gi bi ch-ng trnh chnhhoc cc ch-ng trnh con khc. Ch-ng trnh con phi -c vit sau lnh kt thc ch-ngtrnhchnh.

Cc ch-ng trnh x l ngtcng l mt b phn ca ch-ng trnh. Nu cn s dng,

cc ch-ng trnh x l ngt phi -c vit sau lnh kt thc ch-ng trnh chnh.Cc ch-ng trnh con -c nhm li thnh mt nhm sau ch-ng trnh chnh, tip n

l cc ch-ng trnh x l ngt. Bng cch vit nh- vy, cu trc ch-ng trnh -c r rngv thun tinhn trong vic sa v hiu chnh ch-ng trnh sau ny. Tuy nhin c th t dotrn ln cc ch-ng trnh con v cc ch-ng trnh x l ngt ng sau ch-ng trnh chnh.

1.10.2. Cc b-c lp trnh

Ngn ng lp trnh, s tip cn vn c h thng c th ci thin kh nng to ra ccch-ng trnh cht l-ng cao trong thi gian ngn. K thut thit k c h thng gm ccb-c sau:

Xc nh qu trnh cng ngh (trnh t hot ng ca h thng cng ngh) cniu khin.

Xc nh cc thit bng vo v ng ra;phn phi a chcc ng vo v ng ra. Xc nh thut ton v vit ch-ng trnh iu khin. Bin dch v np ch-ng trnh vo PLC. Kim tra v g ri ch-ng trnh. Lp thnh ti liu mi ng-i s dng u hiu s hot ng ca ch-ng trnh

.

Xc nh qu trnh cng ngh. Tr-c tin, ta phi xc nh thit b hay h thng nomun iu khin, chng gm nhng b phn thit b no, quan h gia cc b phn . Mcch cui cng ca b iu khin l iu khin mt h thng hot ng.

S vn hnh ca h thng -c kim tra bi cc thit b u vo. N nhn tn hiu vgi tn hiu n CPU, CPU x l tn hiu v gi n n thit b xut iu khin s hotng ca h thng nh- lp trnh sn trong ch-ng trnh

Xc nh ng vo, ng ra.Tt c cc thit b xut, nhp bn ngoi u -c kt nivi b iu khin lp trnh. Thit b nhp l nhng contact, cm bin... Thit b xut lnhng cun dy, valve in t, motor, b hin th...

Xc nh thut ton v vit ch-ng trnh. Sau khi xc nh tt c cc thit bxut/nhp cn thit, ta nh v cc thit b vo/ra t-ng ng cho tng ng vo/ra trn PLCtr-c khi lp thut ton v vit ch-ng trnh. Thut ton l th t cc b-c xc nh ph-ng


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php gii quyt vn . iu ny th-ng -c thc hin bng l-u hoc vit bng thutgii, k c s dng cc t BEGIN, DO, END, IF-THEN-ELSE, WHILE-DO...

Khi vit ch-ng trnh theo s hnh bc thang (ladder) phi theo s hot ng tun ttng b-c ca h thng.C th s dng cc phn mm ca cc hng sn xut PLC xydng ch-ng trnh iu khin.

Np ch-ng trnh vo b nh.By gi chng ta c th cung cp ngun cho b iu

khin c lp trnh thng qua cng I/O. Bin dch v sau np ch-ng trnh vo b nhthng qua b console lp trnh hay my tnh c cha phn mm lp trnh hnh thang. Sau khinp xong, kim tra li bng hm chun on. Nu -c, cnm phng ton b hot ngca h thng chc chn rng chung trnh hot ng tt.

Chy ch-ng trnh. Tr-c khi nhn nt Start, phi chc chn rng cc dy dn ni ccng vo, ra n cc thit b nhp, xut -c ni ng theo ch nh. Lc PLC mi btu hot ng thc s. Trong khi chy ch-ng trnh, nu b li th my tnh hoc b Consoles bo li, ta phi sa li cho n khi n hot ng an ton .

Thut ton th hin trn hnh 1.27.

Xc nh yu cu cah thng iu khin

V l-u chung ca hthng iu khin

Lit k tt c cc ng ra, ng vo nit-ng i n cc cng I/O ca PLC

Chuyn l-u sangs hnh thang

Np lp trnh s hnhthang thit k cho PLC

M phng ch-ng trnh vsa li phn mm

Hiu chnh ch-ngtrnh cho ph hp

Ch-ngtrnh OK


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Hnh 1.27. Thut ton lp trnh PLC

1.10.3. Kt ni linh kin vo/ra (nhp/xut)

Trn hnh 1.28a l mch in c in thng dng gm mt nt n PB1, hai cng tc LSv mtn PL. Chng kt ni vi nhau nhm iu khin n PL. Cn trn hnh 1.28b l ktni ca h thng iu khin bng PLC. Cc nt n v cng tc lp ti cc u vo, cn nlp ti u ra ca PLC. Ch rng gia hnh ny l phn ch-ng trnh PLC, chng thhin mi quan h ca nt bm, cc cng tcv bng n t-ng t nh- s kt ni cngca mch in c in.

Chy th ch-ng trnh

Hiu nh liphn mm

Np ch-ng trnhvo EPROM

Lp h sh thng chott c cc bn v

END

Ch-ngtrnh OK


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a

b

Hnh 1.28

1.10.4. V d lp trnh PLC

Xt hot ng ca van tr-t thu lc iu khin xi lanh v lp ch-ng trnh iu khinchng. Hnh1.29 minh ha van tr-t 4/3 (4 cng bav tr). Khi cp ngun cho cun htsolenoid tri (Q0.0), cng P(k hiu ngun cung cp p sut) -c ni vi A. Do chophp cht lng thy lc l-u thng t Pn Avi lanh chy sang phi. Du ngn bn phitrv thng cha qua B. Khi cp ngun cho cun ht solenoid phi, cht lng thy lc l-uthng t Pn Bvo bn ngn phi xi lanh lm piston chy sang tri, cn du bn ngn tritrv thng cha qua A.

Hnh 1.29. Van tr-t 4 cng 3v tr (4/3) iu khin xi lanh.


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Hy quan st hai ng h tnh gi u xc lp 10s. Khi ng cc tip im khi ngX400, ng h nh gi T450 khi ng, ng thi c tn hiu ra t Y431. Ng ra Y431 lmt trong cc solenoid -c s dng kch hot van. Khi -c cp in, Y431 ht co tr-tca van sang phi lm dng kh nn to ra p sut P tc dng vo u bn phi ca xi lanh,khoang tri xi lanh -c ni vi thng vi kh quyn. Do piston di chuyn v bn tri.

Sau 10s cc tip im th-ng m T450 ng v cc tipim th-ng ng T450 m.iu ny ngn chn ng ra Y431, khi ng ng h nh gi T451 v cp ngun cho ngra Y480. Khi , ngun p sut Ptc dng vo pha bn tri piston v pha bn phi -c nikt vi l thng kh quyn. Lc ny piston di chuyn v bn phi. Sau , cc tip imth-ng ng T451 s m, lm cho cc tip im th-ng ng T450 ng, nh Y431 -ccp in. T y chui lnh iu khin s lp li.

Documents

Cau Truc Va Nguyen Ly Hoat Dong Cua PLC S7-200