TI:

Nhim v thit k:mch m thi gian v o nhit I/Mch o nhit . o nhit t 0100 dng cm bin LM335 o nhit mi trng by gi tr nn kh n gin v d lm. Khng cn phi nhit k thy ngn na m chng ta hy ng dng nhng kin thc hc vo lm 1 mch o nhit n gin. Mt phn ci thin kin thc lp trnh v cch x l tn hiu tng t sang s m chng ta gi tt l ADC. Mt iu y ch cn hiu bn cht ca vn l c. bi ny chng ti dng chip vi iu khin PSoc (11 bit) v Dspic (10bit) x l tn hiu ny.

A.Chun b linh kin : + 1 con cm bin nhit LM335 : 9K n 12K + 1 con chip Psoc CY8C29466 hay l Dspic30f4011 + 1 con LCD 16*2 hin th kt qu + Thm vo l vi linh kin c bn nh bin tr, t in,... Tm hiu cm bin LM335 Hnh dng ca LM335 ngoi thc t :

N c 3 chn chnh : 2 chn cp ngun v 1 chn out tn hiu Analog

Khi ta cp in p 5V cho LM335 th nhit o c t cm bin s chuyn thnh in p tng ng ti chn s 2 (Vout). in p ny c t l vi gii nhit m n o c. Vi gii ca nhit u ra l 10mV/K. Hot ng trong gii in p t 0 cho n 5V v gii nhit o c t 0 oC n 100oC. V cn ch n nhng thng s chnh sau : + Hot ng chnh xc dng in u vo t 0.4mA n 5mA. Dng in u vo ngoi khong ny kt qu o s sai + in p cp vo n nh l 5V + Tr khng u ra thp 1 m + Gii nhit mi trng l t 0 n 100 C Nh vy LM335 n cho chng ta tn hiu tng t (Analog) v chng phi x l tn hiu ny thnh nhit .

B.Tnh ton cc gi tr ca mch o Do tn hiu tr v t cm bin LM335 l tn hiu tng t . Nh vy x l tn hiu ny v cho ra kt qu nhit tng ng th ta cn dng b bin i tng t sang s gi tt l ADC. u bi l o nhit t 0 n 100 C Nh ta bit phn gii nhit ca LM335 l 10mV/ K nn ta c + Ti 0 C th in p u ra ti LM335 l 2.73V + Ti 100 C th in p u ra LM335 l 3.73V Nh vy gii in p m ADC bin i l t (2.73V n 3.73V) tc l 1V Gi S l gii in p o ca tn hiu : S = (2.73 3.73V) tc l 1V A l gii in p ca ADC : A = 5V Ta c trong con Dspic tch hp sn b khi ADC 10 bit tc cao v trong con Psoc n cng tch hp sn b ADC 11 bit nn s dng b ADC ny cho mc ch bin i. Ta c bc thay i ca ADC 10 bit : n = 5 /1024 = 4.9mV (Dspic) n1 = 5/2047 = 2.44mV (Psoc Sai s tng i ca mch o = 0.0049/1 = 0.49% (Dspic) 1 = 0.00244/1 = 0.244% (Psoc)

C.Tnh gi tr nhit u ra LM335 l cm bin nhit , vi nhit u ra l 10mV/K S dng b bin i ADC_10bit : + c gi tr ln nht l 1024 + vi V = V = 5V + Bc thay i l : (Ca Dspic v Psoc)n = 5/1024 = 4.9 (mV) (Dspic) n1 = 5/2047 = 2.44(mV) (Psoc) Nn ti 0 C hay 273K th in p u ra LM335 c gi tr l 2.73V Nn ti 100 C hay 373K th in p u ra ca LM335 c gi tr l : 373.10mV/K = 3.73V. Nh vy gii in p u vo s l (2.73 n 3.73V) Tnh ton c gi tr ADC c c t Lm335. + V_in = 2.73V =>ADC_value = (1024/5).2.73 = 559 (Dspic) + V_in = 3.73V => ADC_value = (1024/5).3.73 = 764 (Dspic) + V_in = 2.73V => ADC_value = (2047/5)*2.73 = 1118 (Psoc) + V_in = 3.73 => ADC_value = (2047/5)*3.73 = 1527 (Psoc) Mt khc do ADC_value = 1 cho ra in p tng ng l 4.9mV (dspic) v 2.44mV (Psoc). Trong khi LM335 cho ra in p l 10mV/K. Nn do ADC _value thay i trong 1 n v th nhit phi thay i l : (4.9mV/10mV/K) = 0.5K (dspic) v (2.44mV/10mV/K) = 0.244K (Psoc) Nh vy ta c cng thc tnh y ra C tng ng cho c Psoc v Dspic:

t = (ADC_value 559)* (4.9mV/10mV) = (ADC_value 559) * 0.49 (i vi Dspic) t = (ADC_value - 1118) * (2.44mV/10mV) = (ADC_value - 1118) * 0.244 (i vi Psoc) 5) Tnh gi tr in tr m cho LM355 Mun p ra ng vi 10mV/oK th phi cp dng cho n t 400uA n 5mA, vy phi c in tr m. Nu dng ngun p 5V, di o t 0-100 C => p trn LM335 s t 2.73V n 3.73V => p ri trn in tr s l t 2.27V n 1.27V => chn in tr 1.5k ni 5V - 1,5k - LM335. Do in tr 1.5K khng c nn ta dng bin tr cho in tr m l 1.5K.iu chnh gitrijij in tr ny cho nhit ng vi gi tr nhit mu.

D. S phn cng ca mch o

E) nh gi u nhc im ca mch thit k Psoc chng ti vit trn phn mn bin dch ca PSoc Desiger v ngn ng l C. V cn Dspic ti vit trn mi trng Mplad v ngn ng l C30 + i vi chng trnh ca Psoc th ti ch vit l o c nhit v gi tr nhit ch hin th ln LCD. Ngoi ra ko c chc nng no. + i vi chng trnh vit trn Dspic th ti lm kh nhiu chc nng : o nhit v cnh bo nhit nhp t bn phm (Ma trn phm). Trong chng trnh th qu trnh nhp bn phm cha c ti u khng c nhp ngon lnh nh bn phm my tnh, Sau khi cnh bo th chng trnh phi reset li. Trong qu trnh thc hin cn ch . Cn hiu qu trnh bin i ADC nh tc ly mu, qu trnh lc s cho tn hiu. Trong y ca chng ti khng c qu trnh lc s cho tn hiu.Trong qu trnh cn hiu chnh nhit ng vi gi tr thc ca mi trng.

8) Mt vi hnh nh ca mch o + Mch o i vi Psoc

+ Mch o khi lm vi Dspic

II/Mch m thi gian. Mch m thi gian

Xt mch m phng mch m c bn dng IC m 7490 nh sau:

1. Phn to xung clock: C th dng Tranistor hoc IC nhng thng

th hng ta dng mch to xung s dng IC NE555 d g 5. S S mch to xun h ng:

S S chn NE555: n

2. IC m: Dng IC 74LS90 S S chn IC 7490: n

S S cng logic: g

* Ch : + Chn CP0: Chn kch xung clock. +MR1, MR2: chn reset. + Cc chn Q0,Q1,Q2, Q3: Cc ng ra ca IC m a vo Input ca IC gii m. y l mch m c bn m t 0 n 9. Ta c th thit k m n 1 s N bt k bng cch ni ng ra Q3( bit cao) ca tng th n n chn CP0 ca tng th (n+1) 3. IC gii m: Dng IC 74LS48:

Cc u vo t A0 n A3 tng ng vi cc s BCD c chn. LED s hin th cc s ny theo bng sau:

T T s c bn ny ta thit k mch ng h s. S m phng y k ca mch ng h s :

Mch ny khng m t 00:00:00 n 99:99:99 m s m n 23:59:59. V y l mch ng h nn xung clock a vo phi c chu k 1giy( tn s 1Hz). i vi IC iu khin vic m giy, ngay lc LED hin th chuyn t trng thi 59 giy sang 60 giy , ta dng IC 7408 (Cng AND u tin t trn xung) Reset IC 7490 th nht. Lc ny chn Reset s cng trng thi vi u ra ca cng AND th nht ( mc 1) , u ra ny cn c ni vi chn xung clock CP0 ca IC m pht. Mt xung clock c kch v IC m pht m ln 1 n v. Tng t nh th i vi IC m pht . Ring i vi IC m gi, trng thi n lm cho LED hin th 24 cng chnh l lc n Reset. S nh phn tng ng ca 2 l Q3Q2Q1Q0=0010 v ca 4 l Q3Q2Q1Q0=0100. V vy u ra ti Q1 ca IC m gi ( m hng chc) v Q2 ca IC m gi ( m hng n v) c a vo 7408( cng AND th 3 t trn xung) . u ra t cng AND ny s c a vo chn Reset ca 2 IC m gi. V vy trng thi tip theo s l 00:00:00.