Ukumelana netheminali yebhasi ye-CAN kuvamise ukuba ngu-120 ohms. Eqinisweni, lapho uklama, kunezintambo ezimbili zokumelana ne-60 ohms, futhi ngokuvamile kunamanodi amabili angu-120Ω ebhasini. Empeleni, abantu abazi ibhasi elincane le-CAN bancane. Wonke umuntu uyakwazi lokhu.
Kunemiphumela emithathu yokumelana netheminali yebhasi ye-CAN:
1. Thuthukisa ikhono lokulwa nokuphazamiseka, vumela isignali yemvamisa ephezulu namandla aphansi ihambe ngokushesha;
2. Qinisekisa ukuthi ibhasi ingena ngokushesha esimweni esifihliwe, ukuze amandla ama-capacitors e-parasitic azohamba ngokushesha;
3. Thuthukisa ikhwalithi yesiginali futhi uyibeke kuzo zombili iziphetho zebhasi ukuze unciphise amandla okubonisa.
1. Thuthukisa ikhono lokulwa nokugxambukela
Ibhasi le-CAN linezifunda ezimbili: “okusobala” kanye “nokufihliwe”. I-“Expressive” imele “0”, “ifihliwe” imele “1″, futhi inqunywa i-transceiver ye-CAN. Isibalo esingezansi siwumdwebo ojwayelekile wesakhiwo sangaphakathi se-transceiver ye-CAN, kanye nebhasi lokuxhuma iCanh neCanl.
Uma ibhasi licacile, i-Q1 yangaphakathi ne-Q2 iyavulwa, futhi umehluko wengcindezi phakathi kwekani nekani; lapho i-Q1 ne-Q2 inqanyulwa, iCanh neCanl zisesimweni sokungenzi lutho ngomehluko wengcindezi ongu-0.
Uma kungekho mthwalo ebhasini, inani lokumelana lomehluko ngesikhathi esifihliwe likhulu kakhulu. Ishubhu ye-MOS yangaphakathi iyisimo sokumelana okuphezulu. Ukuphazamiseka kwangaphandle kudinga kuphela amandla amancane kakhulu ukuze ibhasi likwazi ukungena ebaleni (i-voltage encane yesigaba esijwayelekile se-transceiver. I-500mv kuphela). Ngalesi sikhathi, uma kukhona ukuphazanyiswa kwemodeli ehlukile, kuzoba nokuguquguquka okusobala ebhasini, futhi ayikho indawo yokuthi lokhu kuguquguquka kuthathe, futhi kuzodala isikhundla esicacile ebhasini.
Ngakho-ke, ukuze kuthuthukiswe ikhono lokulwa nokuphazamiseka kwebhasi elifihliwe, lingakhuphula ukumelana nomthwalo ohlukile, futhi inani lokumelana lincane ngangokunokwenzeka ukuvimbela umthelela wamandla amaningi omsindo. Kodwa-ke, ukuze ugweme ibhasi lamanje elidlulele ukuze lifake okucacile, inani lokumelana alikwazi ukuba lincane kakhulu.
2. Qinisekisa ukuthi ungena ngokushesha esimweni esifihliwe
Ngesikhathi sesimo esicacile, i-capacitor ye-parasitic yebhasi izokhokhiswa, futhi lawa ma-capacitor adinga ukukhishwa lapho ebuyela esimweni esifihliwe. Uma kungekho mthwalo wokumelana obekwe phakathi kwe-CANH neCanl, i-capacitance ingathululwa kuphela ngokumelana okuhlukile ngaphakathi kwe-transceiver. Le impedance inkulu uma kuqhathaniswa. Ngokwezici zomjikelezo wesihlungi se-RC, isikhathi sokukhipha sizoba side kakhulu. Sengeza i-capacitor engu-220pf phakathi kweCanh neCanl ye-transceiver yokuhlolwa kwe-analog. Izinga lesikhundla ngu-500kbit/s. I-waveform iboniswa esithombeni. Ukwehla kwalolu hlobo lwamagagasi kuyisimo eside uma kuqhathaniswa.
Ukuze ukhiphe ngokushesha ama-capacitor e-parasitic webhasi futhi uqinisekise ukuthi ibhasi lingena ngokushesha endaweni efihliwe, ukumelana nomthwalo kufanele kubekwe phakathi kwe-CANH neCanl. Ngemva kokwengeza i-resistor engu-60Ω, ama-waveforms ayaboniswa emfanekisweni. Kusuka esibalweni, isikhathi lapho ubuyela ngokusobala ekuwohlokeni komnotho sincishiselwa ku-128ns, okulingana nesikhathi sokusungulwa kokucacisa.
3. Thuthukisa ikhwalithi yesiginali
Uma isignali iphezulu ngezinga eliphezulu lokuguqulwa, amandla onqenqema lwesignali azokhiqiza ukubonakaliswa kwesignali uma i-impedance ingafaniswa; isakhiwo sejometri sesigaba sesiphambano sekhebula lokudlulisela siyashintsha, izici zekhebula zizoshintsha ngaleso sikhathi, futhi ukucabangela kuzophinde kubangele ukucabangela. Ingqikithi
Lapho amandla eboniswa, i-waveform ebangela ukubonakaliswa iphakama ngaphezu kwe-waveform yasekuqaleni, ezokhiqiza izinsimbi.
Ekupheleni kwekhebula lebhasi, izinguquko ezisheshayo ku-impedance zibangela ukubonakaliswa kwamandla esignali, futhi insimbi ikhiqizwa esignali yebhasi. Uma insimbi inkulu kakhulu, izophazamisa ikhwalithi yokuxhumana. Itheminali resistor ene-impedance efanayo yezimpawu zekhebula ingangezwa ekupheleni kwekhebula, engamunca le ngxenye yamandla futhi igweme ukukhiqizwa kwezinsimbi.
Abanye abantu benze uhlolo lwe-analog (izithombe zikopishwe yimi), izinga lokuma lalingu-1MBIT/s, i-transceiver Canh neCanl zixhume imigqa esontekile engu-10m, futhi i-transistor yayixhunywe ku-resistor engu-120Ω ukuze kuqinisekiswe isikhathi sokuguqulwa esifihliwe. Akukho mthwalo ekugcineni. I-waveform yesiginali yokuphela iboniswa emfanekisweni, futhi unqenqema lwesignali olukhuphukayo luvela insimbi.
Uma i-resistor engu-120Ω ingezwa ekugcineni komugqa osontekile, i-waveform yesiginali yokugcina iba ngcono kakhulu, futhi insimbi iyanyamalala.
Ngokuvamile, ku-topology yomugqa oqondile, zombili iziphetho zekhebula ziwukuphela kokuthumela kanye nesiphetho sokwamukela. Ngakho-ke, ukumelana netheminali eyodwa kufanele kwengezwe kuzo zombili iziphetho zekhebula.
Enqubweni yangempela yokufaka isicelo, ibhasi le-CAN ngokuvamile aliwona umklamo ophelele wohlobo lwebhasi. Izikhathi eziningi kuyisakhiwo esixubile sohlobo lwebhasi nohlobo lwenkanyezi. Isakhiwo esijwayelekile sebhasi le-analog CAN.
Kungani ukhetha i-120Ω?
Kuyini impedance? Kusayensi kagesi, isithiyo samanje kumjikelezo ngokuvamile sibizwa ngokuthi impedance. Iyunithi ye-impedance ithi Ohm, evame ukusetshenziswa ngu-Z, okuwubuningi z = r+i (ωl – 1/(ωc)). Ngokuqondile, i-impedance ingahlukaniswa izingxenye ezimbili, ukumelana (izingxenye zangempela) kanye nokumelana nogesi (izingxenye ezingokoqobo). Ukumelana nogesi kufaka phakathi amandla kanye nokumelana nezinzwa. I-current ebangelwa ama-capacitors ibizwa ngokuthi i-capacitance, futhi okwamanje okubangelwa i-inductance ibizwa ngokuthi ukumelana nezinzwa. I-impedance lapha ibhekisela ekubunjweni kuka-Z.
I-impedance yesici yanoma iyiphi ikhebula ingatholwa ngokuhlolwa. Ngakolunye uhlangothi lwekhebula, ijeneretha yegagasi yesikwele, enye ekugcineni ixhunywe ku-resistor eguquguqukayo, futhi ibheka i-waveform ekuphikisaneni nge-oscilloscope. Lungisa usayizi wevelu yokumelana kuze kube yilapho isignali ekuphikisaneni kuyinsimbi enhle engenawo amagagasi ayisikwele: ukufanisa i-impedance nobuqotho besignali. Ngalesi sikhathi, inani lokumelana lingabhekwa njengokuhambisana nezici zekhebula.
Sebenzisa izintambo ezimbili ezijwayelekile ezisetshenziswa izimoto ezimbili ukuze uzihlanekezele zibe imigqa esontekile, futhi isici singatholwa ngendlela engenhla cishe engu-120Ω. Lokhu futhi ukumelana nesiphetho esinconywe yizinga le-CAN. Ngakho-ke Ayibalwa ngokusekelwe ezicini zangempela zomugqa womugqa. Vele, zikhona izincazelo ezisezingeni le-ISO 11898-2.
Kungani kufanele ngikhethe i-0.25W?
Lokhu kufanele kubalwe kuhlanganiswe nesimo esithile sokwehluleka. Zonke izixhumanisi zemoto ye-ECU zidinga ukucabangela i-short -circuit emandleni kanye ne-short-circuit phansi, ngakho-ke sidinga ukucabangela isifunda esifushane ekunikezeni amandla ebhasi le-CAN. Ngokwezinga, sidinga ukucabangela isifunda esifushane ukuya ku-18V. Uma sicabanga ukuthi i-CANH imfushane ku-18V, yamanje izogeleza iye ku-Canl ngokumelana ne-terminal, futhi ngenxa Amandla we-resistor engu-120Ω ngu-50mA*50mA*120Ω = 0.3W. Uma ucabangela ukuncishiswa kwenani ekushiseni okuphezulu, amandla okumelana nokuphela kwe-0.5W.
Isikhathi sokuthumela: Jul-08-2023
