Ukuba wakha wabukela irobhothi yomfundi ye-Arduino enamavili amabini irhubuluza phambili imizuzu esibhozo, ingcangcazele, ize icime ngokukhawuleza (reboot) ngalo lonke ixesha isivamvo se-ultrasonic (ultrasonic sensor) sibangela ukuba ijike, uhlangabezene nengxaki yebhetri ye-PP3 9V. Ibhetri ayinasiphako. Ifunwa nje ukuba yenze umsebenzi ifiziksi engazange yayilela wona.

Ibhetri eqhelekileyo enecala-xande ye-9V iphelelwa ngamandla ngokukhawuleza kwiiprojekthi zeerobhothi zasezikolweni ngenxa yezinto ezintathu ezidibeneyo: amandla amancinci agcinwe ngaphakathi, ukungavumi kwangaphakathi okuphezulu (high internal resistance) okubangela ukuhla okukhulu kwevolthi phantsi komthwalo weemotha, kunye nokulahleka kobushushu kwisilawuli-volthi esiyi-linear (linear voltage regulator) esikwibhodi ye-Arduino. Ukuqonda izibalo ezingemva kokusilela oku kwenza kube lula ukukhetha iindlela zombane ezinexabiso eliphantsi nezomelele ngakumbi kwigumbi lokufundela.

Yintoni Engaphakathi Kwibhetri ye-9V?

Xa uxobula isikhuseli sesinyithi sebhetri ye-alkaline PP3 9V eqhelekileyo, uya kufumana iiseli ezincinci eziyisilinda ezintandathu ze-1.5V (ezihlala zibizwa ngokuba yi-AAAA) ezidityaniswe ngokulandelelana (in series). Ngenxa yokuba ezi seli zincinci kakhulu, amandla azo eekhemikhali ewonke aphantsi ngokumangalisayo—ngokuqhelekileyo aphakathi kwe-400 milliamp-hours (mAh) kunye ne-550mAh xa ikhutshwa kancinci kakhulu.

Okona kubalulekileyo, abavelisi beebhetri balinganisa lawo mandla phantsi kweemeko ezifanelekileyo: umthwalo oqhubekayo we-15 ukuya kwi-25 milliamps (mA) kuphela, eqhelekileyo kwisilumkisi-mosi okanye kwimultimeter yedijithali. Xa ifakwe kwiprojekthi ye-Arduino eqhuba iimotha ezimbini ezityheli ze-TT geared DC (etsala i-200mA ukuya kwi-400mA inye) kunye ne-microcontroller, isivamvo se-ultrasonic, kunye nomqhubi weemotha we-H-bridge, umbane otsalwayo (current draw) udlula ngokulula kwi-500mA ukuya kwi-800mA. Phantsi kwaloo mthwalo unzima, amandla anokusetyenziswa eseli ye-9V ehla kakhulu abe yinxalenye encinci yexabiso layo elilinganisiweyo.

Izibalo Zokuhla Kwevolthi (Voltage Sag) Kunye ne-Brownouts

Ibhetri nganye inokungavumi kwangaphakathi ($R_{int}$). Kwibhetri entsha ye-alkaline 9V, ukungavumi kwangaphakathi kuqala phakathi kwe-$1.5\,\Omega$ ne-$2.0\,\Omega$, kwaye kunyuka kakhulu njengoko ibhetri iphelelwa ngamandla.

Xa umbane ($I$) utsalwa, ivolthi ephuma kwiziphelo zebhetri ($V_{terminal}$) yehla ngokwendlela yefomula ethi:

$$V_{terminal} = V_{open} - (I \times R_{int})$$

Khawucinge ngokwenzekayo xa irobhothi ehambayo ye-Arduino iqala iimotha zayo imile. Umbane okhawulezileyo wokuqala (stall current) weemotha ezincinci ezimbini ze-DC ungafikelela lula kwi-1.0A:

• Ivolthi yesekethe evulekileyo: 9.0V
• Ukuhla kwevolthi kunqamlezo lokungavumi kwangaphakathi: $1.0\text{A} \times 2.0\,\Omega = 2.0\text{V}$
• Ivolthi yesiphelo yangelo xesha: $9.0\text{V} - 2.0\text{V} = 7.0\text{V}$

Njengoko ibhetri iphelelwa ngamandla kancinci kwimizuzu elishumi kwaye ukungavumi kwangaphakathi kunyuka kufikelele kwi-$3.5\,\Omega$, olo nyuko lwe-1.0A luhlisela ivolthi yesiphelo kwi-$5.5\text{V}$. Iibhodi ze-Arduino Uno ne-Nano zisebenzisa izilawuli ezikwibhodi eziyi-linear (njenge-AMS1117 okanye i-LM1117) ukuvelisa amandla azinzileyo e-5V afunwa yi-microcontroller ye-ATmega328P. Ezi zilawuli zifuna ivolthi eyongezelelweyo ebizwa ngokuba yi-"dropout voltage" emalunga ne-1.0V ukuya kwi-1.2V. Xa ivolthi engenayo isihla ngaphantsi kwemalunga ne-6.2V, amandla e-5V ayawa, nto leyo ebangela isekethe ye-brownout reset ye-microcontroller ukuba isebenze. Irobhothi iyazicima ize izivule kwakhona, iimotha ziyema, umthwalo uyaphela, ivolthi ibuyela kwi-8V, i-Arduino iyaphinda iqale, kwaye lo mjikelo uyaphindaphindeka ngokungenasiphelo.

Ilahleko Yesilawuli-Mbane Esi-linear

Nangaphambi kokuba ivolthi yebhetri ihle ifikelele kwi-brownout, ukusebenzisa i-Arduino ngebhetri ye-9V usebenzisa iphini le-VIN okanye i-barrel jack kuchitha phantse isiqingatha samandla ebhetri njengobushushu nje obungenanzuzo.

Isilawuli esiyi-linear sehlisa ivolthi ngokusebenza njengesinqandi-mbane esiguqukayo (variable resistor). Sichitha ivolthi engaphezulu ($V_{in} - V_{out}$) iphinda-phindwe ngombane ohamba kuso:

$$P_{loss} = (V_{in} - 5\text{V}) \times I$$

Xa wehlisa i-9V usiya kwi-5V, ulahla i-4V kuyo yonke i-9V enikeziweyo—ukusebenza kakuhle kombane (electrical efficiency) okungama-55% kuphela. I-44% eseleyo yamandla abizayo ebhetri yakho itshiswa njengobushushu kwi-chip encinci yesilawuli esikwibhodi.

Uthelekiso Lwemithombo Yombane Kwizifundo Zeerobhothi Zasezikolweni

Yintoni Onokuyisebenzisa Endaweni Yayo Eklasini

Kumagumbi okufundela ezikolo zamabanga aphantsi naphakamileyo akha iiprojekthi phantsi kwekharityhulam esemthethweni ye-Coding and Robotics, ukuyeka iibhetri ze-9V konga imali eninzi yohlahlo lwabiwo-mali kwaye kuphelisa nexesha lokufuna iingxaki eklasini.

1. Isibambi-Bhetri se-4xAA okanye 6xAA

Iiseli eziqhelekileyo ze-AA zinamandla aphindaphindwe kane ukuya kahlanu kuneebhetri ze-9V kwaye zinokungavumi kwangaphakathi okuphantsi kakhulu. Ipakethe ye-4xAA inika i-6.0V (alkaline) okanye i-4.8V (NiMH), enokunika amandla abaqhubi beemotha ze-DC ngqo ngelixa isondla amandla alawulweyo e-logic. Ipakethe ye-6xAA (7.2V–9.0V) ibonelela ngevolthi eyongezelelweyo eyaneleyo kwiphini le-VIN le-Arduino ngaphandle kokuhla kufikelele kwi-brownout xa iimotha ziqala ukusebenza.

2. Umbane Weendlela Ezimbini (Ukwahlula Iimotha Kwii-Microcontroller)

Eyona ndlela icocekileyo yobunjineli kukwahlula amandla e-logic kumandla eemotha. Nika amandla i-microcontroller ye-Arduino ngezibuko layo le-USB usebenzisa i-power bank efikelelekayo, ehlawulwayo ye-5V yeseli enye. Nika amandla iimotha nomqhubi we-H-bridge usebenzisa ipakethe yebhetri eyodwa ye-4xAA. Dibanisa iingcingo zomhlaba (GND) zayo yomibini le mithombo kunye. Xa iimotha zima okanye zitsala umbane omkhulu ngesiquphe, ukuhla kwevolthi kwenzeka kuphela kwibhetri yeemotha, nto leyo eshiya amandla e-5V e-microcontroller eqinile engachaphazeleki.

3. Iipakethe ze-2S 18650 Li-ion Ezine-Step-Down Buck Converter

Kumaqela eerobhothi ezikolo zamabanga aphakamileyo akhuphisana kukhuphiswano lwezixhobo ezivulelekileyo ezifana ne-WRO RoboMission, iiseli eziqhelekileyo ze-lithium-ion 18650 kulungelelwaniso lwe-2S (7.4V eqhelekileyo) zinika amandla aphezulu kakhulu. Endaweni yokufaka i-7.4V kwisilawuli esiyi-linear esingasebenzi kakuhle se-Arduino, qhagamshela ibhetri usebenzisa i-converter ehlisayo (buck converter) efikelelekayo esetelwe kwi-5.0V. Izilawuli ze-switching zisebenza ngomlinganiselo wokusebenza kakuhle ophakathi kwama-85% nama-95% kwaye azitshisi ivolthi engaphezulu njengobushushu.

Qinisekisa ukuba nasiphi na isibambi-bhetri se-18650 esisetyenziswa ezikolweni siquka iisekethe ezakhelwe ngaphakathi zokukhusela ibhetri (BMS) ukuthintela ukukhutshwa kwamandla ngokugqithisileyo, iisekethe ezimfutshane (short-circuits), kunye neengozi zokujika kweziphelo ezichaseneyo (reverse polarity) ngexesha abafundi beziphatha.

Iindleko Zolu Tshintsho

EMzantsi Afrika, ibhetri enye ye-alkaline 9V ixabisa phakathi kwe-R40 ne-R65. Kwiklasi yabafundi abangama-30 abasebenza ngababini kwikota yeeveki ezilishumi, ukutshintsha iibhetri ze-9V eziphelileyo rhoqo emva kwezifundo ezintathu zokuziqhelanisa kubiza isikolo ngaphezulu kwe-R2,500 ngekota kwizinto ezithengwa rhoqo. Ukuxhobisa izakhelo zeerobhothi ngeeseli ezihlawulwayo ze-NiMH AA okanye iipakethe ezikhuselweyo ze-lithium-ion ezivela kwi-khathalogu yezinto ye-Sheen Robotics kuzihlawulela ngokwazo kwiijikelezo ezimbini zeeprojekthi ngelixa kuphelisa ukukhathazeka kokuzicima nokuzivula kweerobhothi phakathi kwemiboniso.