CHNG 3XY DNG M HNH H THNG CN BNG NH LNG3.1. M HNH CN BNG NH
LNGng c s dng l ng c khng ng b ba pha roto lng sc, tc ng c o c nh
my pht tc v a v b iu khin.B iu khin PLC iu chnh tc ca bng ti v lu
lng im liu sao cho tng ng vi gi tr t.Cm bin trng lng Loadcell s bin
i trng lng nhn c trn bng thnh tn hiu in a v b khuch i. B khuch i s
khuch i tn hiu nhn c t t bo cn v a v b iu khin. Tn hiu thu c l ti
trng tc thi m t bo cn o c kt hp vi tn hiu nhn c t my pht tc xc nh
khong thi gian (khong thi gian tr ) m on bng i t t bo cn n im
liu.Sau khong thi gian tr lu lng ti im liu ca cn nh lng l kt qu ca
tch s gia lng ti trn mt n v chiu di ca bng (o c lc i qua t bo cn)
vi tc hin thi ca on bng .B iu khin PID c nhim v iu chnh sai lch gia
lu lng t v lu lng thc, khuch i v trit tiu sai lch ch tnh. Tn hiu u
ra ca b PID c a n iu khin bin tn ng c, lm cho tc ng c truyn ng bng
ti thay i sao cho lu lng ti im liu tng ng vi lu lng t.3.2. THNG S
CA CC THIT B TRONG H THNG
Di RngMt bngLu lngTi nh mc trn bngChiu di cu cnng knh tang
quayTc bng nh mcT bo cnTi trng nh mc ca t bo cnng c ng c truyn ng l
ng c xoay chiu Tc ng c in p nh mcDng nh mcTn s nh mcCng sut nh mcHp
gim tcT s truynB o tc My pht tc a ra tn hiu in tB bin tnB bin tn
TOSHIBA VnC1-2000TNH CHN LINH KIN CHO NGUN CP CHO LOADCELL
Ngun cung cp cho Loadcell phi l b ngun n p m bo chnh xc, n nh,
vi cp in p 5V v 12V. Tnh chn linh kin to ra b ngun n p vi cp in p
5V v 12V: Ngun n p l mt thit b c nhim v n nh in p mt chiu ra ti khi
in p v tn s ca li thay i hoc khi ti bin i. Trong thc t, cc b ngun n
p c phn thnh 3 loi nh sau: Loi dng cc linh kin nh iot n p n nh
ngun: loi ny thng dng cho nhng trng hp yu cu dng ti khng qu vi chc
mA v n nh dng in ra khng qu vi phn trm. Khng ph hp cho nhng n p tay
i trong phm vi ln v khi cc Diode v in tr s b t nng qu mc gy nn hng
hc. Loi dng cc Tranzitor: c th kt hp vi nhng Diode n p, cho php tng
dng ti ln n vi ampe, song vi cng ngh IC pht trin th loi ny thng t c
s dng. Loi dng cc IC chuyn dng thc hin n p: yl phng php thng c ng
dng rt rng ri v gi thnh r, tin cy cao. Cc IC n p thng m bo dng ra
khong 100mA 1A, in p ra ti 50V.Trong n ny em s dng phng php dng IC
chuyn dng to mch ngun n p. to ngun 5V s dng IC7805, to ngun 12V s
dng IC7812. y l 2 IC thuc h IC 78xx c ch to cng nghip vi cp in p
chun. Cp in p c th hin bng hai s cui trong tn IC. Dng ti cho php ca
h IC ny l 1.5 (A). S nguyn l mch ngun:
Hnh 3.x. S ngun cp cho Loadcell v mch khuch iu vo ca mch ngun l
in p 220V xoay chiu qua bin p, vo b chnh lu cu 1 pha thnh in p mt
chiu, in p ny s c a vo hai IC ngun l LM7805 v LM7812 to ngun in p
mt chiu n nh 5V v 12V. Cc Diode trong chnh lu cu c la chn l loi
1N5402 c I=2A v in p U=70V.T C1 v C4 c chc nng lm gim gn sng, nng
cao mc in p mt chiu ln gn bng mc in p cc i, lm kho cha in n nh cp
in cho ti. Chn loi t 2200F - 35V .T C2 v C5 c tc dng hn ch hin tng
dao ng t kch trong IC. La chn loi t 470F - 35V.T C3 v C6 c chc nng
lc cc sng hi v nhiu cao tn, la chn loi 0.1F-40V.Hai in tr hn dng
cho hai Led bo trng thi dng loi 220 Ohm.
