n iu khin logic c th lp trnh

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O MC CHT LNG DNG CM BIN SIU MNguyn Thanh in, Thnh Duy Lm Thnh Hip1,Trn L Trung Chnh2

ABSTRACTThis research aims to design a measurement system of tanks in factorys by using transceiver ultrasonic module SRF-06 and expansion module EM231 of PLC S7-200. PLC( Programmable logic control) computes value of liquid level from the converted value of ADC in EM231 and shows it in text display TD200. Keyword: measuring liquid level, ultrasonic sensor Title: Measuring liquid level using ultrasonic sensor

TM TT ti nghin cu ny nhm mc ch thit k h thng o lng mc cht lng ca cc bn cha trong cc nh my bng cch s dng module thu pht siu m SRF-06 v module m rng EM231 ca PLC S7-200. PLC( Programmable logic control) tnh ton gi tr mc cht lng t gi tr chuyn i ca b ADC ca module EM231 v truyn gi tr hin th ln mn hnh TD200. T kha: o mc cht lng, cm bin siu m

1 GI THIU Hin nay trong cc nh my cng nghip, vic o lng v gim st h thng cc bn cha gn nh t ng hon ton. Tuy nhin tnh n nh v bn ca h thng cn ty thuc vo thit b s dng v phng php thit k. Vic o lng c th dng cc loi cm bin khc nhau nh cm bin siu m, cm bin p sut, hoc n gin l dng phao ni,kt hp vi vi iu khin hoc PCL. ti ny mong mun thit k mt h thng o lng mc cht lng ca h thng bn cha bng cch dng cm bin siu m v PLC vi tin cy 1 cm da trn phn mm Step7-MicroWin v m phng kt qu trn phn mm S7-200. 2 PHNG PHP THC HIN 2.1 Tng quan Nguyn l ca o khong cch bng sng siu m l iu khin cm bin pht siu m pht ra mt chui xung, sau thi gian lan truyn trong mi trng khng kh nu gp vt cn th sng siu m s phn x ngc li. Thi gian sng siu m lan truyn t cm bin pht n i tng v phn x li cm bin thu ph thuc vo khong cch t cm bin n vt cn. Vn tc ca sng siu m truyn trong khng kh b nh hng bi cc yu t mi trng, nhng mt cch tng i ta

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Nhm sinh vin lp K Thut iu Khin K35 B mn T ng Ha, Khoa Cng Ngh, H Cn Th

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n iu khin logic c th lp trnh

Trng i hc Cn Th

c th ly vn tc truyn sng siu m trong khng kh v = 350 m/s ( 30oC). T ta tnh c khong cch cn tm theo cng thc:d= 350.t ( m) 2

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trong t (s) l thi gian t lc pht n lc nhn li sng siu m. Nh th bit chnh xc mc cht lng trong bn th phi lp li qu trnh phtthu-x l mt cch lin tc. Trong bi nghin cu ny s dng module SRF-06, trn c sn cc mch in t v vi iu khin iu khin qu trnh pht, thu v x l tn hiu. EM231 l module m rng ca PLC S7-200, module ny c 4 ng vo tng t. Tn hiu ng vo c th l in th (0 - 10 V, 0 - 5 V, 5 V, 2.5 V) hay dng in (0 20 mA). Gi tr analog u vo c chuyn i tng ng thnh mt gi tr nh phn v lu trong vng nh AIWx, kch tht l 1 word. 2.2 Thit k phn phn mm

Hnh 1. nh dng gi tr nh phn ca mt knh chuyn i ADC ca EM231

Theo nh Hnh 1 th gi tr chuyn i c trong ch n cc ca ng vo th ch 13 bit ln nht trong vng nh cha gi tr chuyn i, trong bit MSB ca vng nh ny lun bng 0 (s dng), tc l gi tr chuyn i ch cha trong 12 bit (212 = 4096). V vy mun c ng gi tr chuyn i c th ta phi chia AIW0 cho 8 (tc l dch phi vng nh ny 3 bit). i vi module SRF06, gi tr ng ra t 1 5V tng ng vi khong o t 0 510 cm, nhng thang tham chiu trong ADC ca EM235 li t 0 5V nn gi tr nh nht ca vng nh AIW0 lun l 819 khi ng ra ca SRF-06 l 1V. V th ta cn a cn hiu chnh gi tr ny tr v 0 khi hin th ra TD-200. Khi ng ra ca SRF-06 thay i gi tr ( ln hn 1V) th gi tr AIW0 khng cn ng theo thang o ca SRF-06 v th ta tnh khong cch o c theo cng thc nh sau:d= AIW 0 819 (cm) 4095 819 510

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Nh vy, vi mt bn cha bit trc chiu cao, mc cht lng ti a, ti thiu trong qu trnh vn hnh ta c th lp t cm bin sao cho mc cao nht (c th) khng chm ti b cm bin. Khi ta bit c khong cch t y bn ti b cm bin l(cm) v c th d dng tnh ra c cao mc cht lng so vi y bn (h) l: h= l d2

(cm)

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n iu khin logic c th lp trnh

Trng i hc Cn Th

Trong gii hn ti ny, nhm nghin cu chn thng s lp t nh sau: Khong cch t y bn n module cm bin l = 450cm, chiu cao ca bn l 400 cm. Tc l khi nc cn st y bn cm bin vn cn o c v khi nc y ti ming bn vn khng chm ti cm bin.

Hnh 2. M hnh m phng

3 KT QU V NH GI Chng trnh m phng thc hin ng nh mc ch thit k, sai s ti a ch 1cm. Tuy nhin, y ch l kt qu m phng nn khng nh gi ht c nhng tc ng thc t bn ngoi, cc yu t nhit , cng v p lc m thanh xung quanh cng nh hng n tc thu/pht ca cm bin siu m.

Hnh 3. Kt qu m phng trn phn mm S7-200 3

n iu khin logic c th lp trnh

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4 KT LUN V NGH Tuy ch mc m phng nhng kt qu tnh ton v thit k ca ti cho thy hon ton c th trin khai h thng ny trn i tng thc t, nhng cng cn c nhng hiu chnh cn thit h thng t c kt qu tt nht. Vic o mc nc khng n gin l quan st gi tr, v th khi trin khai ngoi thc th cn c nhng pht trin thm nng cao hiu qu s dng PLC nh iu khin h thng my bm n nh mc nc v iu khin cc thit b khc. CM NNhm thc hin chn thnh cm n Ks. Trn L Trung Chnh h tr nhm trong qu trnh nghin cu. ng thi khng qun cm n gia nh to iu kin thun li cng nh ng vin tinh thn nhm vng ch thc hin ti ny.

TI LIU THAM KHOChu Ch c, 2008. K thut iu khin lp trnh PLC SIMATIC S7-200, 277 trang. Nguyn B Hi, Gio trnh l thuyt iu khin logic, Nxb i hc Nng.

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