Kukana kwa basi ya CAN nthawi zambiri kumakhala 120 ohms. M'malo mwake, popanga, pali zingwe ziwiri za 60 ohms kukana, ndipo nthawi zambiri pabasi pamakhala ma node awiri a 120Ω. Kwenikweni, anthu omwe amadziwa basi ya CAN pang'ono ndi pang'ono. Aliyense amadziwa izi.
Pali zotsatira zitatu za kukana mabasi a CAN:
1. Kupititsa patsogolo luso loletsa kusokoneza, lolani chizindikiro chafupipafupi ndi mphamvu zochepa zipite mofulumira;
2. Onetsetsani kuti basiyo imalowetsedwa mwamsanga kumalo obisika, kuti mphamvu ya parasitic capacitors ipite mofulumira;
3. Limbikitsani chizindikiro cha chizindikiro ndikuchiyika pamapeto onse a basi kuti muchepetse mphamvu yowonetsera.
1. Kupititsa patsogolo luso loletsa kusokoneza
Basi ya CAN ili ndi zigawo ziwiri: "zowonekera" ndi "zobisika". "Expressive" imayimira "0", "zobisika" zimayimira "1", ndipo zimatsimikiziridwa ndi transceiver ya CAN. Chithunzi chomwe chili pansipa ndi chithunzi chamkati cha transceiver ya CAN, ndi mabasi olumikizana a Canh ndi Canl.
Pamene basi ikuwonekera, Q1 ndi Q2 yamkati imayatsidwa, ndipo kusiyana kwapakati pakati pa chitha ndi chitha; Q1 ndi Q2 zikadulidwa, Canh ndi Canl zili mumkhalidwe wongokhala ndi kusiyana kwa 0.
Ngati palibe katundu mu basi, mtengo wotsutsa wa kusiyana kwa nthawi yobisika ndi yaikulu kwambiri. Chubu chamkati cha MOS ndizovuta kwambiri. Kusokoneza kwakunja kumangofuna mphamvu yochepa kwambiri kuti basi ilowemo momveka bwino (pafupifupi voteji ya gawo lonse la transceiver. Only 500mv). Panthawiyi, ngati pali kusokoneza kwachitsanzo chosiyana, padzakhala kusinthasintha koonekeratu pabasi, ndipo palibe malo oti kusinthasintha kumeneku kungawatengere, ndipo kudzapanga malo omveka bwino pa basi.
Choncho, pofuna kupititsa patsogolo mphamvu yotsutsa-kusokoneza mabasi obisika, ikhoza kuonjezera kukana kwa katundu wosiyana, ndipo mtengo wotsutsa ndi wochepa kwambiri kuti uteteze kukhudzidwa kwa mphamvu zambiri zaphokoso. Komabe, kuti mupewe mabasi ochulukirapo kuti alowe momveka bwino, mtengo wotsutsa sungakhale wochepa kwambiri.
2. Onetsetsani mwamsanga kulowa mu dziko lobisika
Panthawi yomveka bwino, parasitic capacitor ya basi idzaperekedwa, ndipo ma capacitorswa amafunika kumasulidwa akabwerera kudziko lobisika. Ngati palibe katundu wotsutsa amaikidwa pakati pa CANH ndi Canl, mphamvuyo imatha kutsanuliridwa ndi kukana kosiyana mkati mwa transceiver. Izi impedance ndi yayikulu. Malinga ndi mawonekedwe a RC fyuluta dera, nthawi yotulutsa idzakhala yayitali kwambiri. Timawonjezera 220pf capacitor pakati pa Canh ndi Canl ya transceiver ya mayeso a analogi. Chiwerengero cha malo ndi 500kbit / s. Mawonekedwe a waveform akuwonetsedwa pachithunzichi. Kutsika kwa mawonekedwe a mafundewa ndi dziko lalitali.
Kuti mutulutse mwachangu mabasi a parasitic capacitor ndikuwonetsetsa kuti basi imalowa mwachangu pamalo obisika, kukana katundu kuyenera kuyikidwa pakati pa CANH ndi Canl. Pambuyo powonjezera 60Ω resistor, ma waveform akuwonetsedwa pachithunzichi. Kuchokera pachiwonetsero, nthawi yobwerera momveka bwino pakutsika kwachuma imachepetsedwa mpaka 128ns, zomwe ndizofanana ndi nthawi yokhazikitsidwa momveka bwino.
3. Sinthani khalidwe la chizindikiro
Pamene chizindikirocho chili pamwamba pa kutembenuka kwakukulu, mphamvu ya m'mphepete mwa chizindikiro idzapanga chiwonetsero cha chizindikiro pamene impedance sichikufanana; mawonekedwe a geometric a kusintha kwa gawo la chingwe chopatsirana, mawonekedwe a chingwe adzasintha ndiye, ndipo kuwunikira kudzachititsanso kusinkhasinkha. Essence
Mphamvu ikawonetsedwa, mawonekedwe a mafunde omwe amayambitsa kuwunikira amakhala apamwamba kwambiri ndi mawonekedwe oyambira, omwe amapanga mabelu.
Kumapeto kwa chingwe cha basi, kusintha kofulumira kwa impedance kumapangitsa kuti chizindikiro cha m'mphepete mwake chiwonetsere mphamvu, ndipo belu limapangidwa pa chizindikiro cha basi. Ngati belulo ndi lalikulu kwambiri, lidzakhudza khalidwe la kulankhulana. Chotsutsa chotsiriza chokhala ndi vuto lomwelo la mawonekedwe a chingwe chikhoza kuwonjezeredwa kumapeto kwa chingwe, chomwe chingatenge gawo ili la mphamvu ndikupewa kupanga mabelu.
Anthu ena adayesa mayeso a analogi (zithunzizo zidakopedwa ndi ine), kuchuluka kwa malo kunali 1MBIT / s, transceiver Canh ndi Canl adalumikizana ndi mizere yopotoka ya 10m, ndipo transistor idalumikizidwa ndi 120Ω resistor kuti zitsimikizire kutembenuka kobisika. Palibe katundu pamapeto. Mawonekedwe amtundu wamawonekedwe omaliza akuwonetsedwa pachithunzichi, ndipo chizindikiro chokwera m'mphepete chikuwoneka belu.
Ngati chopinga cha 120Ω chiwonjezedwa kumapeto kwa mzere wokhotakhota, mawonekedwe amtundu wamawonekedwe amawongoleredwa bwino, ndipo belu limasowa.
Nthawi zambiri, mu topology yowongoka, malekezero onse a chingwe ndi malekezero otumiza ndi olandila. Chifukwa chake, kukana kumodzi kumayenera kuwonjezeredwa kumapeto kwa chingwe.
Munjira yeniyeni yogwiritsira ntchito, basi ya CAN nthawi zambiri simapangidwe amtundu wa basi. Nthawi zambiri zimakhala zosakanikirana zamtundu wa basi ndi mtundu wa nyenyezi. Kapangidwe ka basi ya analogi CAN.
Chifukwa chiyani kusankha 120Ω?
Kodi impedance ndi chiyani? Mu sayansi yamagetsi, chopinga chapano muderali nthawi zambiri chimatchedwa impedance. Chigawo cha impedance ndi Ohm, chomwe nthawi zambiri chimagwiritsidwa ntchito ndi Z, chomwe chimakhala chochuluka z = r+i (ωl - 1/(ωc)). Mwachindunji, impedance ikhoza kugawidwa m'magawo awiri, kukana (magawo enieni) ndi kukana magetsi (magawo enieni). Kukaniza kwamagetsi kumaphatikizanso mphamvu komanso kukana zomverera. Zomwe zimayambitsidwa ndi ma capacitors zimatchedwa capacitance, ndipo zomwe zimachitika chifukwa cha inductance zimatchedwa sensory resistance. Kulepheretsa apa kukutanthauza nkhungu ya Z.
Chikhalidwe cha impedance ya chingwe chilichonse chikhoza kupezedwa mwa kuyesa. Pamapeto amodzi a chingwe, jenereta ya square wave, mbali inayo imalumikizidwa ndi chowongolera chosinthika, ndipo imayang'ana mawonekedwe a mafunde pa kukana kudzera mu oscilloscope. Sinthani kukula kwa mtengo wokana mpaka chizindikiro pa kukana ndi belu labwino-free square wave: impedance yofananira ndi kukhulupirika kwa chizindikiro. Panthawiyi, mtengo wotsutsa ukhoza kuonedwa kuti ukugwirizana ndi makhalidwe a chingwe.
Gwiritsani ntchito zingwe ziwiri zomwe zimagwiritsidwa ntchito ndi magalimoto awiri kuti muwapotoze kukhala mizere yokhotakhota, ndipo mawonekedwewo amatha kupezeka ndi njira yomwe ili pamwambapa pafupifupi 120Ω. Uku ndiyenso kukana kukana komwe kumalimbikitsidwa ndi muyezo wa CAN. Chifukwa chake Simawerengeredwa potengera mawonekedwe a mtengo wa mzere weniweni. Zachidziwikire, pali matanthauzidwe mu muyezo wa ISO 11898-2.
Chifukwa chiyani ndiyenera kusankha 0.25W?
Izi ziyenera kuwerengedwa mophatikiza ndi zina zolephera. Mawonekedwe onse agalimoto ECU ayenera kuganizira zazifupi -zozungulira ku mphamvu ndi zazifupi -zozungulira pansi, kotero tiyeneranso kuganizira za dera lalifupi kupita ku magetsi a basi ya CAN. Malinga ndi muyezo, tiyenera kuganizira dera lalifupi kwa 18V. Poganiza kuti CANH ndi yaifupi ku 18V, panopa idzayenda ku Canl kupyolera mu kukana kotsiriza, ndipo chifukwa Mphamvu ya 120Ω resistor ndi 50mA * 50mA * 120Ω = 0.3W. Poganizira kuchepetsedwa kwa kuchuluka kwa kutentha kwakukulu, mphamvu yotsutsa ma terminal ndi 0.5W.
Nthawi yotumiza: Jul-08-2023
