PTZ Control Deep Dive: RS485 Bus Principles, Protocols, and Common Troubleshooting

Labari

18 ga Agusta, 2023

RS485 shine ma'aunin sadarwar serial na daban wanda ke amfani da layin sigina guda biyu (wanda ake kira A da B, ko + da -) don watsa bayanai. Babban fa'idar siginar bambance-bambance shine ƙarfin hana tsangwama mai ƙarfi.

RS485 Layer na Jiki: Ba Wayoyi Biyu bane kawai

RS485 shine ma'aunin sadarwar serial na daban wanda ke amfani da layin sigina guda biyu (wanda ake kira A da B, ko + da -) don watsa bayanai. Babban fa'idar siginar bambance-bambance shine ƙarfin hana tsangwama - mai karɓa yana gano bambancin ƙarfin lantarki tsakanin layin biyu maimakon cikakken ƙarfin lantarki dangane da ƙasa. Wannan yana nufin hayaniyar yanayin gama-gari (kamar tsangwama da injinan da ke kusa da su ke gabatar da su ko mitar mitoci) ana soke su ta atomatik.

Amma fa'idar siginar bambance-bambance ta zo tare da farashi. Bus ɗin RS485 yana buƙatar daidaitattun masu tsayayyar ƙarewa (yawanci 120 ohms) waɗanda aka sanya a ƙarshen bas ɗin don kawar da tunanin sigina. Idan resistor ƙarewa ya ɓace ko shigar da shi a wuri mara kyau, tunanin siginar yana haifar da kurakuran bayanai - yana bayyana azaman sigina da yawa da yin ƙara akan oscilloscope. A cikin aikin injiniya mai amfani, mai bacewar ƙarewa yana ɗaya daga cikin manyan abubuwan da ke haifar da gazawar sarrafa PTZ.

Pelco-D vs Pelco-P: Zabin Protocol Ba Mai Zama Bane

Ka'idojin sarrafa PTZ da aka fi amfani da su a cikin kulawar tsaro sune Pelco-D da Pelco-P. Dukansu ka'idojin sadarwa ne na serial, amma tare da nau'ikan bayanai daban-daban: Pelco-D yana amfani da tsarin 7-byte, yayin da Pelco-P ke amfani da mafi ƙarancin tsari. Ka'idojin biyu ba su dace ba - idan kyamara tana goyan bayan Pelco-D kuma kayan aikin injiniya sun aika umarnin Pelco-P, PTZ ba zai amsa ba.

Ko da ya fi damuwa shi ne cewa aiwatar da nau'ikan nau'ikan daban-daban na ƙa'idar iri ɗaya na iya samun bambance-bambance a hankali. Misali, a wasu abubuwan aiwatarwa na Pelco-D, PTZ saurin rufaffen ya bambanta da ma'auni, yana haifar da raguwar daidaiton sarrafawa. A cikin ayyukan haɗaɗɗiyar alamar, ana ba da shawarar tabbatar da alamar dacewa ta alama ta alama, maimakon ɗaukar 'idan duk suna goyan bayan Pelco-D, sun dace.' Jerin PK69 da PK68 na FangService suna goyan bayan ka'idodin Pelco-D da Pelco-P, kuma suna iya canzawa ta atomatik ko da hannu dangane da alamar kyamara.

Rashin Ganewa gama gari da Gudun Matsala

PTZ sarrafa gazawar matsala na matsala yana buƙatar tsari mai gudana. Shawarar da aka ba da shawarar magance matsalar ita ce: ① duba Layer na jiki (ko kebul na RS485 ba shi da kyau, ko wayoyi na A/B daidai ne, ko an shigar da resistor na ƙarshe); ② bincika Layer na yarjejeniya (ko nau'in yarjejeniya ya dace, ko ƙimar baud daidai yake, ko lambar adireshin daidai); ③ duba Layer kayan aiki (ko PTZ kanta ba ta da kyau, ko samar da wutar lantarki ya isa, ko ɓangaren injin ɗin ya lalace). Rashin gazawar Layer na jiki shine mafi yawan gama-gari - Juya layin A/B shine matsala mafi banƙyama domin a mafi yawan lokuta PTZ har yanzu tana jujjuyawa, kawai a akasin shugabanci. A lokacin gyara kurakurai, idan ka sami PTZ ya 'juya hagu' lokacin da ya kamata ya 'juya dama,' da farko duba wayar A/B. Wani batu na yau da kullun shine RS485 multixing line tare da nau'i-nau'i na waya marasa aiki a cikin kebul na cibiyar sadarwa - idan nau'ikan waya da aka yi amfani da su don RS485 a cikin kebul ɗin suna da ƙima mara daidaituwa tare da nau'ikan bayanan, tsangwama na iya haifar da shi. Jerin PK69 na FangService yana da aikin gwajin kebul na RS485 da aka gina a ciki wanda zai iya gano ci gaba da kebul, gajerun da'irori, da ƙetare. Haɗe tare da aikin bincike na yarjejeniya, zai iya gano wuri na gazawar da sauri.

RS485 Cibiyar Sadarwar Topology da Iyakokin Nisa

Topology bas RS485 da iyakokin nisa sune ƙuntatawa a sauƙaƙe a cikin ƙirar injiniya. Ma'auni na RS485 yana ba da shawarar nau'in nau'in bas - duk na'urori masu daidaitawa akan babban layi guda ɗaya, tare da resistor ƙarewa a kowane ƙarshen babban layin. Tauraro topology (duk na'urorin da ke da alaƙa da kansu zuwa tsakiyar wuri) suna haifar da tunanin sigina, wanda zai iya haifar da gazawar sadarwa koda a ɗan gajeren nesa.

Matsakaicin nisa na sadarwa na RS485 ya yi daidai da ƙimar baud. A ƙaramin baud na 9600bps, matsakaicin nisa zai iya kaiwa mita 1200; a babban adadin baud na 115200bps, matsakaicin nisa yawanci bai wuce mita 200 ba. Idan an rarraba na'urorin PTZ a cikin aikin a kan nesa mai nisa, yi la'akari da ƙara masu maimaitawa ko rage ƙimar baud. FangService's PK69 da PK68 jerin, a cikin RS485 gwajin yanayin, iya nuna halin yanzu sadarwa sigogi (baud rate, data bits, tasha ragowa, daidaici), taimaka injiniyoyi da sauri tabbatar da cewa sanyi ne daidai.

Daga RS485 zuwa IP PTZ Control: Juyin Halitta na Fasahar Sadarwa

Ana aiwatar da sarrafa PTZ na al'ada ta hanyar bas na RS485, amma yayin da kyamarori na IP suka zama ruwan dare, sarrafa PTZ yana haɓaka zuwa hanyoyin tushen hanyar sadarwar IP. IP PTZ na zamani na iya karɓar umarnin sarrafawa kai tsaye akan kebul na cibiyar sadarwa ta hanyar ka'idar ONVIF ko ka'idojin mallakar mallakar mai siyarwa, yana kawar da buƙatar cabling RS485 mai zaman kanta.

Amma RS485 ba zai ɓace ba nan da nan. A cikin coaxial HD tsarin (AHD / TVI / CVI), kulawar PTZ har yanzu yana dogara ne akan RS485; a cikin adadi mai yawa na tsarin gargajiya da aka riga aka shigar, RS485 ita ce kawai hanyar sarrafawa. Saboda haka, ko da a cikin lokacin IP, RS485 PTZ iko ya kasance muhimmiyar fasaha ga injiniyoyin tsaro. Layin gwajin gwajin hanyar sadarwa na FangService yana rufe duka gwajin sarrafa RS485 PTZ (jerin PK68/PK69) da gwajin hanyar sadarwar IP (jerin PK69), yana ba da cikakkiyar mafita na gwaji don tsarin gargajiya da na zamani. Don gaurayawan ayyukan da suka haɗa da sababbi da tsofaffin tsarin, wannan ƙarfin ɗaukar hoto biyu yana da mahimmanci musamman. View the Network Test Instruments Collection