Uxhathiso lwesikhululo sebhasi ye-CAN luqhelekile luyi-120 ohms. Ngapha koko, xa uyilwa, zimbini ii-60 ohms zokuxhathisa umtya, kwaye kukho iindawo ezimbini ze-120Ω ngokubanzi ebhasini. Ngokusisiseko, abantu abayaziyo ibhasi encinci ye-CAN bancinci. Wonke umntu uyayazi le nto.
Kukho iziphumo ezintathu zokuxhathisa kwisikhululo sebhasi ye-CAN:
1. Ukuphucula ikhono lokuchasana nokuphazamiseka, vumela umqondiso we-frequency ephezulu kunye namandla aphantsi ahambe ngokukhawuleza;
2. Qinisekisa ukuba ibhasi ifakwe ngokukhawuleza kwisimo esifihlakeleyo, ukwenzela ukuba amandla e-parasitic capacitors aya kuhamba ngokukhawuleza;
3. Ukuphucula umgangatho wesignali kwaye uyibeke kuzo zombini iziphelo zebhasi ukunciphisa amandla okubonakalisa.
1. Ukuphucula amandla okuthintela ukuphazamiseka
Ibhasi ye-CAN inamazwe amabini: "ecacileyo" kunye "efihliweyo". "I-Expressive" imele "0", "ifihliwe" imele "1", kwaye igqitywe yi-CAN transceiver. Umzobo ongezantsi ngumzobo oqhelekileyo wesakhiwo sangaphakathi se-CAN transceiver, kunye neCanh kunye neCanl uxhumano lwebhasi.
Xa ibhasi icacile, i-Q1 yangaphakathi kunye ne-Q2 ivuliwe, kunye nokwahlukana koxinzelelo phakathi kwe-can kunye ne-can; xa i-Q1 kunye ne-Q2 zinqunyulwa, i-Canh kunye ne-Canl zikwimeko engabonakaliyo kunye nokwahlukana koxinzelelo lwe-0.
Ukuba akukho mthwalo ebhasini, ixabiso lokuchasana lomahluko kwixesha elifihliweyo likhulu kakhulu. Ityhubhu ye-MOS yangaphakathi yimeko ephezulu yokuchasa. Ukuphazamiseka kwangaphandle kufuna kuphela amandla amancinci kakhulu ukwenzela ukuba ibhasi ingene ecacileyo (i-voltage encinci yecandelo eliqhelekileyo le-transceiver. Kuphela i-500mv). Ngeli xesha, ukuba kukho ukuphazanyiswa kwemodeli eyahlukileyo, kuya kubakho ukuguquguquka okucacileyo kwibhasi, kwaye akukho ndawo yokuba oku kuguquguquka ukufunxa, kwaye kuya kudala indawo ecacileyo ebhasini.
Ngoko ke, ukuze kuphuculwe ikhono lokuchasana nokuphazamiseka kwebhasi efihliweyo, kunokunyusa ukuchasana komthwalo ohlukeneyo, kwaye ixabiso lokumelana lincinci kangangoko ukuthintela impembelelo yamandla amaninzi engxolo. Nangona kunjalo, ukwenzela ukuba ugweme ibhasi yangoku ngokugqithisileyo ukuba ingene ecacileyo, ixabiso lokumelana alikwazi ukuba lincinci.
2. Qinisekisa ukungena ngokukhawuleza kwimeko efihliweyo
Ngexesha lesimo esicacileyo, i-parasitic capacitor yebhasi iya kuhlawuliswa, kwaye ezi capacitors kufuneka zikhutshwe xa zibuyela kwimeko efihliweyo. Ukuba akukho mthwalo wokuchasana obekwe phakathi kwe-CANH kunye neCanl, i-capacitance inokuthululelwa kuphela ngokumelana nokwahlukana ngaphakathi kwe-transceiver. Le impedance inkulu. Ngokweempawu ze-RC filter circuit, ixesha lokukhutshwa liya kuba lide kakhulu. Songeza i-220pf capacitor phakathi kweCanh kunye neCanl ye-transceiver yovavanyo lwe-analog. Izinga lendawo yi-500kbit/s. I-waveform iboniswe kumzobo. Ukwehla kolu tshintsho yimeko ende.
Ukuze ukhuphe ngokukhawuleza i-bus parasitic capacitors kwaye uqinisekise ukuba ibhasi ingena ngokukhawuleza kwimeko efihliweyo, ukuchasana nomthwalo kufuneka kubekwe phakathi kwe-CANH kunye neCanl. Emva kokongeza i60Ω isixhasi, iifom zamaza ziboniswa kumzobo. Ukususela kumanani, ixesha lokubuyela ngokucacileyo kwi-recession liyancipha ukuya kwi-128ns, elilingana nexesha lokusekwa kokucaca.
3. Ukuphucula umgangatho womqondiso
Xa umqondiso uphezulu kwizinga eliphezulu lokuguqulwa, amandla omgca wesignali uya kuvelisa ukubonakaliswa komqondiso xa i-impedance ingahambelani; ulwakhiwo lwejometri yotshintsho lwecandelo lomnqamlezo wekhebula, iimpawu zentambo ziya kutshintsha ngoko, kwaye ukubonakalisa kuya kubangela ukubonakaliswa. Undoqo
Xa amandla ebonakaliswa, i-waveform ebangela ukuba ibonakaliswe ibekwe phezulu kunye ne-original waveform, eya kuvelisa iintsimbi.
Ekupheleni kwekhebula lebhasi, utshintsho olukhawulezayo kwi-impedance lubangela ukubonakaliswa kwamandla e-signal, kwaye intsimbi iveliswa kwisignali yebhasi. Ukuba intsimbi inkulu kakhulu, iya kuchaphazela umgangatho wonxibelelwano. I-resistor ye-terminal ene-impedance efanayo yeempawu zentambo inokongezwa ekupheleni kwentambo, enokuthi ithathe le nxalenye yamandla kwaye igweme ukuveliswa kweentsimbi.
Abanye abantu baqhube uvavanyo lwe-analog (imifanekiso ikopishwe ndim), izinga lesikhundla laliyi-1MBIT / s, i-transceiver Canh kunye neCanl zixhumeke malunga nemigca ephothiweyo ye-10m, kwaye i-transistor idityaniswe kwi-120.Ω resistor ukuqinisekisa ixesha lokuguqulwa efihliweyo. Akukho mthwalo ekugqibeleni. I-waveform yesignali yokuphela iboniswa emfanekisweni, kwaye i-signal edge yokunyuka ibonakala intsimbi.
Ukuba i120Ω i-resistor yongezwa ekupheleni komgca ojijekileyo, i-waveform yesignali yesiphelo iphuculwe kakhulu, kwaye intsimbi iyanyamalala.
Ngokuqhelekileyo, kwi-topology ye-straight-line, zombini iziphelo zentambo zisiphelo sokuthumela kunye nesiphelo sokufumana. Ngoko ke, ukuchasana kwe-terminal kufuneka kufakwe kuzo zombini iziphelo zentambo.
Kweyona nkqubo yesicelo, ibhasi ye-CAN ayiloyilo loyilo lwebhasi olugqibeleleyo. Amaxesha amaninzi sisakhiwo esixubeneyo sohlobo lwebhasi kunye nohlobo lwenkwenkwezi. Ubume bomgangatho we-analog CAN ibhasi.
Kutheni ukhetha i-120Ω?
Yintoni impedance? Kwisayensi yombane, umqobo kwi-current in circuit udla ngokuba yi-impedance. Iyunithi ye-impedance yi-Ohm, esetyenziswa rhoqo ngu-Z, esisininzi z = r+i (ωl -1/(ωc)). Ngokukodwa, i-impedance inokwahlulwa ibe ngamacandelo amabini, ukuchasana (amacandelo okwenene) kunye nokumelana nombane (iindawo ezibonakalayo). Ukuxhathisa kombane kukwabandakanya i-capacitance kunye nokumelana noluvo. Ikhoyo ngoku ebangelwa yi-capacitors ibizwa ngokuba yi-capacitance, kwaye yangoku ebangelwa yi-inductance ibizwa ngokuba yi-sensory resistance. Uthintelo apha lubhekisa kubumba uZ.
I-impedance yeempawu zayo nayiphi na intambo inokufumaneka ngovavanyo. Kwesinye isiphelo sentambo, i-square wave generator, esinye isiphelo siqhagamshelwe kwi-resistor eguquguqukayo, kwaye ibona i-waveform ekuchaseni nge-oscilloscope. Lungisa ubungakanani bexabiso lokumelana kude kube ngumqondiso wokuchasana yintsimbi elungileyo-ekhululekileyo yesikwere samaza: ukuhambelana kwe-impedance kunye nengqibelelo yomqondiso. Ngeli xesha, ixabiso lokumelana linokuthi lithathwe lihambelana neempawu zekhebula.
Sebenzisa iintambo ezimbini eziqhelekileyo ezisetyenziswa ziimoto ezimbini ukuzigqwetha zibe yimigca ejijekileyo, kwaye imbonakalo yokuthintela inokufunyanwa ngale ndlela ingasentla malunga ne-120.Ω. Oku kwakhona ukuxhathisa i-terminal ukuxhathisa okucetyiswa ngumgangatho we-CAN. Ngoko ke Akubalwa ngokusekelwe kwiimpawu ze-beam zangempela. Ewe kunjalo, kukho iinkcazo kumgangatho we-ISO 11898-2.
Kutheni kufuneka ndikhethe i-0.25W?
Oku kufuneka kubalwe ngokudibanisa nemo ethile yokungaphumeleli. Zonke ii-interfaces zemoto ECU kufuneka ziqwalasele i-short-circuit kumandla kunye ne-short-circuit emhlabeni, ngoko ke kufuneka siqwalasele isiphaluka esifutshane kunikezelo lwamandla ebhasi ye-CAN. Ngokomgangatho, kufuneka siqwalasele isiphaluka esifutshane ukuya kwi-18V. Ukucinga ukuba i-CANH imfutshane kwi-18V, okwangoku iya kuhamba kwi-Canl ngokuchasana kwe-terminal, kwaye ngenxa Amandla e-120Ω isixhasi yi-50mA*50mA*120Ω = 0.3W. Ukuqwalasela ukunciphisa inani kwiqondo lokushisa eliphezulu, amandla okumelana nokuphela kwe-0.5W.
Ixesha lokuposa: Jul-05-2023
