Iisensa ezitshiphu zomswakamo womhlaba ezineempondo ezimbini ziyaphela emva kweentsuku ezimbalwa egadini yesikolo, kuba eneneni zizekethe zokupleyitha ngombane ezisebenza ngokuchasene. Xa ushiya isensa ye-resistive enemizila evulekileyo ixhunywe kumgca we-3.3V okanye we-5V emhlabeni omanzi, otyebe ngeeminerali, umsinga wombane othe ngqo (DC) ongapheliyo uqhuba i-electrolysis ekhawulezayo. Iprobhu epozitivu isebenza njenge-anode: iyafakwa i-oksijini ize incithe upleyithi lwayo lobhedu emhlabeni de umzila uqhawuke ngokupheleleyo.

Kwizikolo zoMzantsi Afrika ezakha iiprojekthi zonkcenkceshelo oluziqhubayo okanye zolimo olukrelekrele phantsi kwekharityhulam ye-CAPS yeCoding neRobotics, le ndlela yokusilela iguqula iprojekthi ethatha ikota yonke ibe luvavanyo olufileyo phambi kokuba kuntshule isithole sokuqala. Ngethamsanqa, isisombululo asifuni ziiprobhu zoshishino ezidulu okanye uyilo olutsha oluntsonkothileyo.

IKhemistri: kutheni iiprobhu ze-resistive zizitshabalalisa

Iisensa eziqhelekileyo ze-resistive zomswakamo womhlaba zisebenza ngokudlulisa umsinga wombane phakathi kwemizila emibini evulekileyo edlulisa umbane. Ukumelana nombane phakathi kweempondo kuhamba ngokuchasene nomthamo wamanzi: umhlaba owomileyo unokumelana nombane okuphezulu, ngelixa umhlaba omanzi udlulisa umsinga ngokukhululekileyo.

Noko ke, amanzi asemhlabeni asiyiyo i-H₂O ecocekileyo. Sisisombululo se-electrolyte esiqulethe iityuwa zeeminerali ezinyibilikileyo, ii-nitrate zesichumisi, kunye nee-ion zezinto eziphilayo. Xa kufakwa i-voltage ye-DC engapheliyo:

• Kwenzeka i-anodic oxidation kwiprobhu epozitivu: Ii-athom zobhedu ziphulukana nee-electron zize zinyibilike emhlabeni njengee-ion zobhedu (Cu → Cu²⁺ + 2e^-).
• Kwenzeka i-cathodic reduction kwiprobhu enegethivu: Amanzi okanye ii-ion ze-hydrogen zifumana ii-electron, zidla ngokwenza amaqamza egesi ye-hydrogen amancinci kakhulu okanye zitsale ukubumbeka kweeminerali.
• Imizila yobhedu iyaqhekeka: Emva kweveki enye okanye ezimbini, ungqimba lwegolide okanye lwetoti luyaxobuka, ubhedu obungaphantsi butshintshele kuhlaza okumnyama, ize isekethe ivuleke ngonaphakade.

Amanani afundwa yisensa ayaphambuka kakhulu njengoko intsimbi idleka, into eyenza ukuba nawuphi na umgangatho wempompo ezisebenzelayo ungabi namsebenzi phambi kokuba iprobhu iphele ngokupheleleyo.

Enye indlela 1: iisensa ze-capacitive zomswakamo womhlaba (ezicetyiswayo)

Isisombululo esiqhelekileyo kushishino kwii-microcontroller zemfundo (i-ESP32, i-micro:bit, okanye i-Arduino) yisensa ye-analog ye-capacitive yomswakamo womhlaba (ngokuqhelekileyo ethengiswa njengeprobhu ye-capacitive v1.2 okanye v2.0).

Endaweni yokudlulisa umsinga othe ngqo emhlabeni, iprobhu ye-capacitive ilinganisa utshintsho kwi-capacitance yombane olubangelwa yi-dielectric permittivity yomhlaba. Amanzi ane-relative permittivity ephezulu kakhulu (≈ 80) xa kuthelekiswa nezinto eziqinileyo zomhlaba owomileyo (≈ 3 ukuya ku-5) nomoya (≈ 1). Njengoko umswakamo womhlaba usanda, i-capacitance ejikeleze iprobhu iyenyuka, itshintshe i-frequency yesekethe ye-555-timer esebhodini okanye ye-oscillator ye-frequency ephezulu, ethi ibhodi iyiguqule ibe yi-voltage ye-analog ephumayo.

Kutheni iiprobhu ze-capacitive zingadleki

• Akukho bhedu buvulekileyo emhlabeni: Imizila edlulisa umbane itywinwe ngokupheleleyo phantsi kongqimba lwe-solder mask lwe-PCB. Akukho ntsimbi ichukumisa umhlaba omanzi ngokuthe ngqo.
• Akukho ndlela yomsinga othe ngqo: Ngenxa yokuba akukho sekethe ye-galvanic evaliweyo edlula emanzini omhlaba, i-electrolysis ayinakwenzeka.
• Ukungachaphazeleki bubutyuwa bomhlaba: Iisensa ze-resistive zinika amanani obuxoki omswakamo ophezulu ukuba ufaka isichumisi, kuba ii-ion ezongezelelekileyo zehlisa ukumelana nombane. Iisensa ze-capacitive azichaphazeleki kangako kukudluliswa kombane ziiminerali.

Kwiiseti zemfundo, ukuphonononga iikhithi ezilungele ukusetyenziswa ngoko nangoko njengezo zikwikharityhulam ye-Sheen Robotics Smart Agriculture kunika iisensa ze-capacitive esele zilungelelanisiwe, eziyilelwe ngokukodwa ii-microcontroller zegumbi lokufundela.

Enye indlela 2: amandla alawulwa yisoftwe (ukusebenzisa iiprobhu ze-resistive ngamaxesha)

Ukuba isikolo sakho sele sithenge iseti yegumbi lokufundela yeesensa ezitshiphu ze-resistive kwaye asinakukwazi ukuzitshintsha ngoko nangoko, ungabolula ubomi bazo ukusuka kwiiveki ezimbini ukuya kwiinyanga ezininzi ngokusebenzisa amandla alawulwa yisoftwe.

Endaweni yokuxhuma ipini ye-VCC yesensa ngokuthe ngqo kwipini esisigxina ye-3.3V okanye ye-5V ye-microcontroller, xhuma i-VCC kwipini yedijithali ephumayo (okanye kwi-transistor yokucima nokuvula ukuba isensa itsala umsinga ongaphezu kwalowo ipini ye-GPIO inokuwunika ngokukhuselekileyo):

1. Gcina ipini ye-GPIO yedijithali imiselwe ku-LOW (0V) ngexesha lokulinda okuqhelekileyo.
2. Xa uthatha isifundo (umzekelo, kanye kuyo yonke imizuzu engama-30), misela ipini ye-GPIO ku-HIGH.
3. Linda ii-millisecond ezingama-20 ukuya kwezingama-50 ukuze isifundo se-analog sizinze.
4. Funda ixabiso le-ADC ngepini ye-analog.
5. Ngoko nangoko buyisela ipini ye-GPIO ku-LOW.

Ukunciphisa umjikelo wokusebenza ukusuka kumandla angapheliyo ayi-100% ukuya kwii-millisecond ezingama-50 kwisiqingatha seyure nganye kunciphisa ukuchaphazeleka kwe-electrochemical kukonke malunga nama-99.97%, kucothise ukudleka kube kukurhubuluza okungenamsebenzi.

Uthelekiso olusebenzayo lweeprojekthi ze-IoT zegumbi lokufundela

Ukuxhuma nokukhusela iisensa zasegadini ekusebenzeni

Xa ufaka iiprobhu ze-capacitive kwithaneli yesikolo, kumthala wegadi ophakanyisiweyo, okanye kwisityalo esisembizeni engaphakathi, khumbula iinkcukacha ezintathu zokufaka:

• Yenza i-elektroniki esebhodini ingangeni manzi: Iiprobhu ze-capacitive zikhuselekile emhlabeni ukuya kutsho kumgca omhlophe osalathisayo ophawulwe kwi-PCB. Icandelo eliphezulu lebhodi—eliqulethe i-IC yesurface-mount, ii-resistor, kunye nesihloko sentambo—alingeni manzi. Ukubunjwa kwamathontsi okanye ukunkcenkceshela ngentla kuya kwenza isekethe emfutshane kwezi zinto. Tywina ii-cm ezi-2 eziphezulu ngethyubhu ye-heat-shrink ecacileyo egcwaliswe nge-glue eshushu okanye ngongqimba lwe-silicone.
• Qwalasela i-voltage yokusebenza: Iisensa ezininzi ezitshiphu ze-capacitive zisebenzisa i-IC ye-timer efuna ubuncinane be-3.3V ukuya ku-5V. Xa uxhuma kwiibhodi ze-3.3V ezinjenge-ESP32 okanye i-BBC micro:bit, qinisekisa ukuba olo hlobo lwesensa lunako ukusebenza ngokuzinzileyo kwi-3.3V; ngaphandle koko, umqondiso ophumayo uya kuzaliseka kwi-voltage yomgca nokuba umhlaba umanzi kangakanani.
• Lungelelanisa emoyeni nasemanzini: Amanani akrwada e-ADC (anjengo-0–4095 kwi-ESP32) awathethi nto kubafundi. Yenza abafundi barekhode ixabiso elikrwada emoyeni owomileyo (umgangatho we-0% womswakamo) nelo lixabiso xa itshoniswe kutsho emgceni kwikomityi yamanzi (umgangatho we-100% womswakamo), emva koko babhale imephu elula okanye umsebenzi we-interpolation kwi-MicroPython okanye kwi-MakeCode ukuguqula isifundo sibe yipesenti.

Ukuba uyila iinkqubo ezixhunyiweyo zokubeka esweni okusingqongileyo ekufuneka zimelane nemozulu yoMzantsi Afrika, ukucinywa kombane, neekhefu ezinde zeeholide, jonga kwizicwangciso ezivavanywe egumbini lokufundela kwi-Sheen IoT ukufumana iindlela zehardware esele zingqinisisiwe.