Uma uke wabuka irobhothi le-Arduino elinamasondo amabili lomfundi linwabuzela phambili imizuzu eyisishiyagalombili, lidlikize, bese liqala kabusha ngokuzumayo njalo lapho inzwa ye-ultrasonic (ultrasonic sensor) icindezela ithuba lokujika, usuhlangabezane nenkinga yebhethri le-PP3 9V. Ibhethri alonakele. Lifunwa nje ukuba lenze umsebenzi ifiziksi engakaze iwuklamele wona.

Ibhethri elivamile elingunxande lika-9V liphelelwa amandla ngokushesha emiklamweni yamarobhothi yasezikoleni ngenxa yezinto ezintathu ezihlangene: umthamo omncane kakhulu wamandla angaphakathi, ukumelana kwangaphakathi okuphezulu okubangela ukwehla kakhulu kwamandla kagesi (voltage sag) ngaphansi komthwalo wemoto, kanye nokumosheka kokushisa kwe-linear voltage regulator esebhodi le-Arduino. Ukuqonda izibalo eziyimbangela yalokhu kuhluleka kwenza kube lula ukukhetha izinhlelo zikagesi ezishibhile neziqinile zekilasi.

Yini Engaphakathi Kwebhethri lika-9V?

Uma uhlinza ikhava yensimbi yebhethri elijwayelekile le-alkaline PP3 9V uzothola amaseli amancane ayisithupha ayindilinga angu-1.5V (avame ukubizwa nge-AAAA) axhunywe ngokulandelana (in series). Ngenxa yokuthi lawa maseli mancane kakhulu, umthamo wawo wonke wamakhemikhali uphansi ngendlela ephawulekayo—imvamisa uphakathi kuka-400 milliamp-hours (mAh) no-550mAh lapho ephelelwa amandla kancane kakhulu.

Okubaluleke kakhulu, abenzi bamabhethri balinganisa lowo mthamo ngaphansi kwezimo ezikahle: umthwalo oqhubekayo wama-milliamp (mA) aphakathi kuka-15 no-25 kuphela, okuvamile kumtshina wentuthu (smoke detector) noma imitha yedijithali (digital multimeter). Uma lifakwa kuphrojekthi ye-Arduino eshayela amamotho amabili aphuzi e-TT geared DC (adonsa u-200mA kuya ku-400mA lilinye) kanye ne-microcontroller, inzwa ye-ultrasonic, ne-H-bridge motor driver, amandla adonswayo adlula kalula u-500mA kuya ku-800mA. Ngaphansi kwalowo mthwalo osindayo, umthamo osebenzisekayo weseli lika-9V uwa ube yingxenyana encane yenani lalo elilinganisiwe.

Izibalo Zokwehla Kwe-Voltage kanye Nama-Brownout

Ibhethri ngalinye linokumelana kwangaphakathi ($R_{int}$). Ebhethrini elisha le-alkaline 9V, ukumelana kwangaphakathi kuqala phakathi kuka-$1.5\,\Omega$ no-$2.0\,\Omega$, futhi kukhuphuka ngokushesha njengoba ibhethri liphelelwa amandla.

Lapho kudonswa amandla kagesi ($I$), i-voltage elethwa ezinsikeni zebhethri ($V_{terminal}$) iyawa ngokwefomula ethi:

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

Cabanga ngokwenzekayo lapho i-rover ye-Arduino iqala amamotho ayo isukela lapho imise khona. Amandla wesikhashana wokuma (stall current) amamotho amabili amancane e-DC angafinyelela kalula ku-1.0A:

• I-voltage yesekethe evulekile (Open-circuit voltage): 9.0V
• Ukwehla kwe-voltage ekumelaneni kwangaphakathi: $1.0\text{A} \times 2.0\,\Omega = 2.0\text{V}$
• I-voltage yezinsika ngaleso sikhathi: $9.0\text{V} - 2.0\text{V} = 7.0\text{V}$

Njengoba ibhethri liphelelwa amandla kancane phakathi nemizuzu eyishumi futhi ukumelana kwangaphakathi kukhuphukela ku-$3.5\,\Omega$, lokho kukhula okufanayo kuka-1.0A kuhlisa i-voltage yezinsika iye ku-$5.5\text{V}$. Amabhodi e-Arduino Uno ne-Nano asebenzisa ama-linear regulator asebhodi (njenge-AMS1117 noma i-LM1117) ukukhiqiza ulayini ozinzile ka-5V odingeka yi-microcontroller ye-ATmega328P. Lawa ma-regulator adinga okungenani i-"dropout voltage" ecishe ibe ngu-1.0V kuya ku-1.2V. Lapho i-voltage engenayo yehla ngaphansi kwelinganiselwa ku-6.2V, ulayini ka-5V uyawa, okuvula isekethe yokusetha kabusha ngenxa yokwehla kwamandla (brownout reset circuit) ye-microcontroller. Irobhothi liyazisetha kabusha, amamotho ayama, umthwalo uyanyamalala, i-voltage iphindela ku-8V, i-Arduino iqala kabusha, futhi lo mjikelezo uyaphindaphinda ngokungapheli.

Ukulahlekelwa Okubangelwa yi-Linear Regulator

Ngisho nangaphambi kokuba ibhethri lehlele endaweni ye-brownout, ukuhambisa i-Arduino ngebhethri lika-9V usebenzisa iphini le-VIN noma i-barrel jack kumosha cishe ingxenye yamandla ebhethri njengokushisa nje.

I-linear regulator yehlisa i-voltage ngokusebenza njenge-resistor eguqukayo. Ihlakaza i-voltage eyeqile ($V_{in} - V_{out}$) ephindaphindwe ngamandla kagesi ageleza kuyo:

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

Lapho wehlisa u-9V uya ku-5V, ulahla u-4V kuwo wonke u-9V ohlinzekiwe—okungukusebenza kahle kukagesi ngama-55% kuphela. Amanye ama-44% asele amandla abizayo ebhethri lakho ashiswa njengokushisa ku-chip encane ye-regulator.

Ukuqhathaniswa Kwemithombo Yamandla Yamarobhothi Esikoleni

Yini Ongayisebenzisa Esikhundleni Salokho Ekilasini

Ezakhiweni zamakilasi amabanga aphansi naphakeme ezakha amaphrojekthi ngaphansi kohlaka lwezifundo olushicilelwe lwe-Coding and Robotics, ukusuka kuma-snap ka-9V konga isabelomali esibalulekile futhi kuqeda isikhathi sokuxazulula izinkinga ekilasini.

1. Isibambi Samabhethri se-4xAA noma i-6xAA

Amaseli ajwayelekile e-AA anomthamo wamandla aphindaphindwe kane kuya kahlanu kwebhethri lika-9V nokumelana kwangaphakathi okuphansi kakhulu. Iphakethe le-4xAA lihlinzeka ngo-6.0V (alkaline) noma u-4.8V (NiMH), okunganikeza amandla ngokuqondile kuma-driver emoto ye-DC ngenkathi liphaka ulayini we-logic olawulwayo. Iphakethe le-6xAA (7.2V–9.0V) lihlinzeka ngamandla anele ephini le-VIN le-Arduino ngaphandle kokungena kuma-brownout lapho amamotho evuleka.

2. Amandla ka-Dual-Rail (Ukwahlukanisa Amamotho kuma-Microcontroller)

Indlela yobunjiniyela ehlanzeke kakhulu ukuhlukanisa amandla e-logic emandleni emoto. Nikeza i-microcontroller ye-Arduino amandla ngembobo yayo ye-USB usebenzisa i-power bank engabizi, ewashajwayo ye-cell eyodwa engu-5V. Nikeza amamotho ne-driver ye-H-bridge amandla ngephakethe lamabhethri elizinikele le-4xAA. Xhuma olayini bomhlabathi (GND) bayo yomibili le mithombo ndawonye. Lapho amamotho ema noma ekhuphuka ngokuzumayo, ukwehla kwe-voltage kwenzeka kuphela ebhethrini lemoto, kushiye ulayini ka-5V we-microcontroller uqinile njengedwala.

3. Amaphakethe e-2S 18650 Li-ion ane-Step-Down Buck Converter

Emaqenjini amarobhothi ezikole zamabanga aphakeme ancintisana ezinseleleni zehadiwe evulekile njenge-WRO RoboMission, amaseli ajwayelekile e-lithium-ion 18650 ekucushweni kwe-2S (7.4V nominal) ahlinzeka ngokuminyana kwamandla okuphezulu kakhulu. Esikhundleni sokufaka u-7.4V ku-linear regulator ye-Arduino engasebenzi kahle, xhuma ibhethri nge-switching step-down converter (buck converter) engabizi esethwe ku-5.0V. Ama-switching regulator asebenza ngokusebenza kahle okungama-85% kuya kuma-95% futhi awashisi i-voltage eyeqile njengokushisa.

Qinisekisa ukuthi noma yisiphi isibambi samabhethri se-18650 esisetshenziswa ezikoleni sifaka amasekhethi okuvikela ibhethri akhelwe ngaphakathi (BMS) ukuvimbela ukuphela ngokweqile kwamandla, ama-short-circuit, kanye nezingozi zokuhleleka kwezigxobo okuphambene (reverse polarity) ngesikhathi abafundi bephatha impahla.

Ezezimali Zokushintsha

ENingizimu Afrika, ibhethri elilodwa le-alkaline 9V libiza phakathi kuka-R40 no-R65. Eklasini labafundi abangama-30 abasebenza ngababili esikhathini sethemu yamaviki ayishumi, ukushintsha amabhethri ka-9V aphelelwe amandla njalo ngemuva kwezikhathi ezintathu zokusebenza kwenza isikole sisebenzise kalula imali engaphezulu kuka-R2,500 ngethemu ezintweni ezisetshenziswayo eziphindaphindwayo. Ukuhlomisa i-chassis yerobhothi ngamaseli e-NiMH AA awashajwayo noma amaphakethe e-lithium-ion avikelekile avela ku-khathalogi yezingxenye yakwa-Sheen Robotics kuzikhokhela ngokwako phakathi nemijikelezo emibili yephrojekthi ngenkathi kuqeda ukukhungatheka kokuthi irobhothi liqale kabusha phakathi nendawo lapho kukhonjiswa umsebenzi.