Cov txheej txheem:

Teeb duab neeg hlau rau Arduino: 18 Kauj Ruam (nrog Duab)
Teeb duab neeg hlau rau Arduino: 18 Kauj Ruam (nrog Duab)

Video: Teeb duab neeg hlau rau Arduino: 18 Kauj Ruam (nrog Duab)

Video: Teeb duab neeg hlau rau Arduino: 18 Kauj Ruam (nrog Duab)
Video: It Became Unliveable! ~ Abandoned Home Of The Spenser's In The USA 2024, Hlis ntuj nqeg
Anonim
Image
Image
Teeb duab neeg hlau rau Arduino
Teeb duab neeg hlau rau Arduino
Teeb duab neeg hlau rau Arduino
Teeb duab neeg hlau rau Arduino

Nco tseg: Kuv muaj tus qauv tshiab ntawm tus neeg hlau no uas siv lub tshuab luam ntawv Circuit Circuit, tsim tau yooj yim dua, thiab muaj IR thaiv qhov teeb meem! Txheeb nws ntawm

Kuv tsim txoj haujlwm no rau 10-teev kev cob qhia rau ChickTech.org uas nws lub hom phiaj yog qhia cov poj niam hluas rau cov ncauj lus STEM. Lub hom phiaj rau txoj haujlwm no yog:

  • Yooj yim los tsim.
  • Yooj yim rau txoj haujlwm.
  • Ua tej yam ntxim nyiam.
  • Tus nqi qis yog li cov neeg koom tuaj yeem nqa nws mus tsev thiab kawm txuas ntxiv.

Nrog cov hom phiaj hauv siab, ntawm no yog ob peb qhov kev xaiv tsim:

  • Arduino sib xws kom yooj yim ntawm lub cajmeem.
  • AA roj teeb lub zog rau tus nqi thiab muaj.
  • Stepper motors rau qhov tseeb txav.
  • 3D Luam tawm kom yooj yim ntawm kev kho kom haum.
  • Cwj mem npaj nrog Vaub kib duab rau cov txiaj ntsig nthuav.
  • Qhib Qhov Chaw yog li koj tuaj yeem ua ib qho ntawm koj tus kheej!

Nov yog tus neeg hlau uas tuaj ze tshaj qhov kuv xav ua: https://mirobot.io. Kuv tsis muaj lub tshuab txiav laser thiab xa los ntawm Askiv yog txwv tsis pub. Kuv muaj lub tshuab luam ntawv 3D, yog li kuv twv koj tuaj yeem pom qhov no yuav mus qhov twg…

Tsis txhob cia qhov tsis muaj lub tshuab luam ntawv 3D cuam tshuam koj. Koj tuaj yeem nrhiav cov neeg nyiam ua haujlwm hauv zos txaus siab pab koj ntawm www.3dhubs.com

Nws siv ntau txoj haujlwm, tab sis kuv thov nrog qhov nws tshwm sim. Thiab, Kuv tau kawm me ntsis hauv tus txheej txheem. Qhia rau kuv paub koj xav li cas!

Kauj Ruam 1: Qhov Chaw

Qhov
Qhov
Qhov
Qhov
Qhov
Qhov
Qhov
Qhov

Muaj ntau txoj hauv kev rau lub zog, tsav tsheb, thiab tswj cov neeg hlau. Koj tuaj yeem muaj qhov sib txawv ntawm tes uas yuav ua haujlwm, tab sis cov no yog cov uas kuv tau sim thiab pom tias ua haujlwm tau zoo:

Electronics:

  • 1- Arduino UNO lossis sib npaug- adafruit.com/products/50

    Tam sim no Adafruit tam sim no yog Asmeskas Kev Tsim Khoom rau Arduinos tiag! Tau lawv los ntawm qhov chaw

  • 2- Tsav 5V Stepper- adafruit.com/products/858
  • 1- ULN2803 Darlington Tsav Tsheb - adafruit.com/products/970
  • 1- Ib nrab ntawm lub khob cij me me- adafruit.com/products/64
  • 12- Txiv neej-txiv neej dhia- adafruit.com/products/1956

    Yam tsawg kawg ob yuav tsum yog 6 ", tus so tuaj yeem yog 3"

  • 1- Micro servo- adafruit.com/products/169
  • 1- Txiv neej tus pin header- digikey.com/short/t93cbd
  • 1-2 x AA Holder- digikey.com/short/tz5bd1
  • 1 -3 x AA Holder- digikey.com/short/t5nw1c
  • 1 -470 uF 25V capacitor-www.digikey.com/product-detail/en/ECA-1EM471/P5155-ND/245014
  • 1 -SPDT swb hloov -www.digikey.com/product-detail/en/EG1218/EG1903-ND/101726
  • 1- USB micro cable
  • 5 - AA roj teeb

Kho vajtse:

  • 2- 1 7/8 "ID x 1/8" O-ring- mcmaster.com/#9452K96
  • 1- Caster 5/8 "bearing- mcmaster.com/#96455k58/=yskbki
  • 10- M3 x 8mm lub taub hau taub hau ntsia hlau- mcmaster.com/#92005a118/=z80pbr
  • 4-M3 x 6mm lub taub hau tiaj tus ntsia hlau- mcmaster.com/#91420a116/=yskru0
  • 12- M3 Nut- mcmaster.com/#90591a250/=yskc6u3D
  • 2 - 1/4 "xov tsim 4-20 screws

Cov Ntawv Luam (kos tawm www.3dhubs.com yog tias koj tsis muaj kev nkag mus rau lub tshuab luam ntawv):

  • https://www.thingiverse.com/thing1091401

    • 1 x Pob kabmob caster
    • 1 x Chassis
    • 2 x Log
    • 2 x Stepper bracket
    • 1 x Cwj mem tuav / servo bracket
    • 1 x Caj dab dab tshos
  • Kuv siv qhov kev daws teeb meem qis, 100% sau, thiab tsis muaj kev txhawb nqa. Qhov no yog kwv yees li 4 teev ntawm kev luam ntawv.

Khoom siv:

  • Phillips ntsia hlau tsav tsheb
  • Kub kua nplaum phom
  • Digital ntau-meter
  • Riam riam
  • Crayola cov cim xim

Kauj ruam 2: Nyem Firmware

Ua ntej peb mus deb dhau rau kev tsim kho, cia thauj cov khoom ntsuas mus rau lub microcontroller. Qhov kev tshuaj ntsuam tsuas yog kos rau lub thawv kom peb tuaj yeem tshawb xyuas kom raug thiab qhov ntev.

  1. Rub tawm Arduino software los ntawm www.arduino.cc/en/Main/Software
  2. Qhib Arduino software.
  3. Rub tawm cov ntawv zip txuas thiab unzip nws mus rau Arduino sketchbook qhov chaw.

    Koj tuaj yeem nrhiav (lossis hloov) qhov chaw no hauv Arduino IDE: [File] -> [Preferences] -> "Sketchbook Location"

  4. Thauj cov xeem kos: [File] -> [Sketchbook] -> [TIRL_Arduino_TEST]
  5. Txuas koj Arduino rau koj lub khoos phis tawj nrog USB cable.
  6. Hauv Arduino IDE:

    1. Teeb koj pawg thawj coj: [Cov cuab yeej] -> [Pawg Thawj Coj] -> Koj pawg thawj coj saib.
    2. Teem koj qhov chaw nres nkoj txuas: [Cov cuab yeej] -> [Chaw nres nkoj] -> Feem ntau qhov kawg tau teev tseg.
  7. Upload tus kos duab siv tus xub cim.

Yog tias koj muaj teeb meem, xa mus rau www.arduino.cc/en/Guide/Troubleshooting rau kev pab.

Kauj Ruam 3: Tus Cwj Pwm thiab Cov Roj Teeb

Tus Cwj Pwm thiab Cov Roj Teeb
Tus Cwj Pwm thiab Cov Roj Teeb
Tus Cwj Pwm thiab Cov Roj Teeb
Tus Cwj Pwm thiab Cov Roj Teeb
Tus Cwj Pwm thiab Cov Roj Teeb
Tus Cwj Pwm thiab Cov Roj Teeb
Tus Cwj Pwm thiab Cov Roj Teeb
Tus Cwj Pwm thiab Cov Roj Teeb
  1. Ntxig cov txiv ntoo rau sab saum toj ntawm lub chassis (Duab 1). Tej zaum koj yuav tau nias lawv rau hauv.
  2. Txhim Kho Tus Cwj Pwm nrog Tus Kheej Servo nyob rau sab saum toj ntawm lub chassis (Duab 2 & 3).
  3. Txuas cov roj teeb rau hauv qab ntawm lub chassis siv 3Mx6mm tiaj-taub hau ntsia hlau (Duab 4)

    • Koj xav tau tsawg kawg 5xAA txhawm rau ua kom muaj zog Arduino ntawm nws tus tswj hwm onboard. Rau yuav ua haujlwm ib yam, yog li kuv tau suav qhov rau ob qhov loj me ntawm ob sab.
    • Koj xav kom qhov hnyav txav mus rau tus neeg tsav tsheb, yog li tso 3xAA rau sab nraub qaum.
    • Taw qhia cov neeg tuav kom cov coj mus ze rau kab plaub kab khiav.
  4. Xov roj teeb ua los ntawm txoj kab hluav taws xob txuas (Duab 4).
  5. Rov ua dua rau lwm tus tuav lub roj teeb.

Nco tseg: Tshwj tsis yog qhov tshwj xeeb, cov seem ntawm cov ntsia hlau yog 3Mx8mm lub taub hau taub hau ntswj

Kauj Ruam 4: Stepper Backets

Stepper Backets
Stepper Backets
Stepper Backets
Stepper Backets
Stepper Backets
Stepper Backets
Stepper Backets
Stepper Backets
  1. Ntxig cov txiv ntoo rau hauv lub tog raj kheej thiab txuas lawv rau sab saum toj ntawm lub chassis nrog cov ntsia hlau (Duab 1).
  2. Ntxig tus stepper rau hauv qhov txuas thiab txuas nrog cov ntsia hlau thiab txiv ntseej.
  3. Rov ua dua rau lwm tus bracket.

Kauj ruam 5: Caster

Caster
Caster
Caster
Caster
  1. Ntxig lub pob rau hauv lub caster.

    Tsis txhob yuam nws hauv lossis nws yuav tawg. Siv lub tshuab ziab plaub hau los yog rab phom cua kub kom cov khoom muag muag yog tias xav tau

  2. Txuas tus caster rau sab hauv qab ntawm lub chassis nyob rau hauv pem hauv ntej ntawm lub roj teeb tuav.

Kuv tau sim lwm yam khoom puag ncig zoo li pob zeb, tab sis du thiab hnyav zoo li ua haujlwm tau zoo. Yog tias koj xav tau txoj kab uas hla sib txawv, koj tuaj yeem hloov kho openScad cov ntaub ntawv (https://www.thingiverse.com/thing:1052674) kom haum qhov koj muaj ntawm tes.

Kauj Ruam 6: Creadboard thiab Lub Hlwb

Breadboard thiab Lub Hlwb
Breadboard thiab Lub Hlwb
Breadboard thiab Lub Hlwb
Breadboard thiab Lub Hlwb
Breadboard thiab Lub Hlwb
Breadboard thiab Lub Hlwb
  1. Tshem tawm ib qho ntawm txoj kab hluav taws xob siv rab riam ntse, txiav los ntawm cov nplaum hauv qab (Duab 1).

    Ib txoj kev tsheb nqaj hlau muaj hwj chim (liab) ntawm ntug ntug, lawv lwm qhov tsis zoo (xiav). Kuv khaws thawj qhov txuas, thiab nws yuav phim cov duab thiab cov duab. Yog tias koj siv lwm tus, tsuas yog kho cov xov hlau kom haum

  2. Tuav lub khob cij hla lub rooj chassis, kos qhov chaw uas lawv sib tshuam ntawm ntug (Duab 2).
  3. Siv lub ntug ncaj (zoo li txoj kab hluav taws xob tshem tawm), khij kab thiab txiav los ntawm nraub qaum (Duab 3).
  4. Muab lub khob cij tso rau ntawm lub chassis nrog cov ntsia kov cov nplaum uas nthuav tawm (Duab 4).
  5. Txuas Arduino mus rau lwm sab ntawm lub chassis siv 4-20 ntsia hlau (Duab 5).

Kauj Ruam 7: Capacitor thiab Kev Tso Chaw

Capacitor thiab Qhov Chaw Tso
Capacitor thiab Qhov Chaw Tso
Capacitor thiab Qhov Chaw Tso
Capacitor thiab Qhov Chaw Tso
Capacitor thiab Qhov Chaw Tso
Capacitor thiab Qhov Chaw Tso
Capacitor thiab Qhov Chaw Tso
Capacitor thiab Qhov Chaw Tso
  1. Muab tus neeg tsav tsheb darlington thiab lub zog hloov mus rau lub rooj mov ci (Duab 1).

    • Kuv tau ntxiv cov txiv kab ntxwv dots rau pom kom pom cov cim hauv qab no:

      • Pin 1 ntawm tus tsav tsheb darlington
      • Lub roj teeb tus pin ntawm microtroller. Lub hwj huam hloov "ntawm" txoj haujlwm.
  2. Txiav lub capacitor ua yog tias tsim nyog (ntev dua yog qhov tsis zoo) (Duab 2).
  3. Ntxig lub capacitor rau hauv txoj kab uas raug nyob rau sab saum toj ntawm lub khob cij (Duab 3).

Kauj ruam 8: Lub zog

Fais fab
Fais fab
Fais fab
Fais fab
Fais fab
Fais fab
  1. Nrog lub roj teeb sab xis ua: Txuas kab liab rau thawj tus pin ntawm lub zog hloov pauv (Duab 1).
  2. Txuas cov hlau lead dub mus rau ib qho khoob khoob ntawm microcontroller thiab darlington nti (Duab 1).
  3. Nrog rau lub roj teeb sab laug ua: Txuas kab liab rau tib kab ib yam li cov hlau lead dub ntawm lwm lub roj teeb (Duab 2).
  4. Txuas cov kab dub mus rau txoj kev tsis zoo ntawm lub khob cij (Duab 2).
  5. Txuas lub zog rau lub microcontroller:

    1. Jumper liab los ntawm txoj kev tsheb ciav hlau zoo rau tus pin roj teeb (txiv kab ntxwv teev, Duab 3).
    2. Cov jumper dub los ntawm txoj kev tsis zoo mus rau tus lej cim "G" (Duab 4).
  6. Nruab cov roj teeb thiab hloov lub zog rau (Duab 5).
  7. Koj yuav tsum pom lub teeb ntsuab thiab liab ntawm tus tswj tau los (Duab 6).

Teeb meem:

  • Yog tias lub microcontroller teeb tsis tuaj, tam sim ntawd tua lub hwj chim thiab daws teeb meem:

    • Cov roj teeb tau teeb tsa hauv qhov kev qhia raug?
    • Txheeb xyuas ob lub roj teeb ua qhov chaw nyob.
    • Ob chav kos hloov ua qhov chaw.
    • Siv ntau lub ntsuas los ntsuas cov roj teeb.
    • Siv ntau lub ntsuas los ntsuas cov hluav taws xob kev tsheb nqaj hlau.

Kauj Ruam 9: Stepper Power

Stepper zog
Stepper zog
Stepper zog
Stepper zog
Stepper zog
Stepper zog

Tam sim no koj tau txais lub zog rau lub microcontroller, cia ua kom tiav cov xov hluav taws xob rau cov steppers:

  1. Txuas lub jumper dub los ntawm sab laug sab sauv darlington tus pin rau sab tsis zoo ntawm txoj kev tsheb nqaj hlau (Duab 1).
  2. Txuas lub jumper liab los ntawm sab laug sab laug darlington tus pin rau sab zoo ntawm txoj kev tsheb nqaj hlau (Duab 1).
  3. Txuas lub jumper liab los ntawm sab laug sab darlington tus pin rau ib kab sab xis ntawm darlington (Duab 2).
  4. Ntxig tus pin taub hau rau tus stepper dawb JST txuas (Duab 2).

Kauj ruam 10: Stepper Tswj Teeb liab

Stepper Tswj Teeb liab
Stepper Tswj Teeb liab
Stepper Tswj Teeb liab
Stepper Tswj Teeb liab
Stepper Tswj Teeb liab
Stepper Tswj Teeb liab

Lub microcontroller muab 5 volt teeb liab rau darlington array uas nyob rau hauv, muab VCC rau stepper coils:

  1. Pib nrog tus pin nyob ib sab ntawm tus pin hauv av ntawm tus tsav tsheb darlington, thiab teeb cov txiv kab ntxwv, daj, ntsuab, thiab xiav nyob hauv qhov kev txiav txim ntawd (Duab 1).
  2. Txuas cov dhia mus rau tus pin arduino hauv qab no (Duab 2):

    1. txiv kab ntxwv - Digital pin 4
    2. daj - Digital pin 5
    3. ntsuab - Digital pin 6
    4. xiav - Tus lej digital 7
  3. Rov qab ntawm darlington, txuas ntxiv jumper rau lwm tus stepper hauv qhov rov qab ntawm lwm tus:

    xiav, ntsuab, daj, thiab txiv kab ntxwv (Duab 3)

  4. Txuas cov dhia mus rau tus pin arduino hauv qab no (Duab 4):

    1. xiav - Digital pin 9 (tus pin 8 siv tom kawg rau servo).
    2. ntsuab - Digital pin 10
    3. daj - Digital pin 11
    4. txiv kab ntxwv - Tus lej digital 12

Kauj Ruam 11: Kev Sib Txuas Stepper

Stepper Chev Txuas
Stepper Chev Txuas
Stepper Chev Txuas
Stepper Chev Txuas
Stepper Chev Txuas
Stepper Chev Txuas

Tus stepper tus dawb JST txuas txuas rau tus pin header. Cov hlau lead liab yog lub zog, thiab yuav tsum phim cov liab lub zog dhia peb tau teeb tsa ua ntej (Duab 1).

Txhua xim yuav tsum sib phim rau cov microcontroller jumpers nyob rau sab nraud ntawm darlington, tshwj tsis yog ntsuab, uas sib phim cov xim liab ntawm tus stepper (Duab 2).

Kauj ruam 12: Servo

Servo
Servo
Servo
Servo
Servo
Servo
  1. Txhim kho lub tshuab raj horn nrog lub servo tig raws lub moos raws qhov nres thiab lub tshuab raj kab rov tav (Duab 1).
  2. Txuas tus servo rau tus tuav, thiab lub suab taw qhia rau sab xis tus ncej (Duab 1).
  3. Txuas cov xim av (av), liab (5V lub zog), thiab dawb (teeb liab) dhia mus rau hauv qhov txuas txuas, sib piv cov xim servo hlau (Duab 2).
  4. Txuas lub hwj chim thiab cov dhia dhia mus rau hauv av thiab 5V lub taub hau ntawm Arduino (Duab 3).
  5. Txuas lub xov tooj liab liab mus rau Arduino's Digital Pin 8 (Duab 4).

Kauj Ruam 13: Log

Log
Log
Log
Log
  1. Muab cov roj hmab o-ring nyob ib ncig ntawm lub log (Duab 1).
  2. Yog tias lub hauv paus haum ntawm lub qag xoob, koj tuaj yeem siv 3M ntsia hlau los tuav nws hauv qhov chaw (Duab 2).

    Tsis txhob nruj nws ntau dhau lossis koj yuav hle cov yas

Kauj Ruam 14: Xeem

Vam tias koj twb tau tshaj tawm cov firmware hauv Kauj Ruam 2. Yog tias tsis yog, ua tam sim no.

Qhov kev sim firmware tsuas yog kos ib lub xwmfab ntau zaus yog li peb tuaj yeem tshawb xyuas cov lus qhia thiab raug.

  1. Muab koj tus neeg hlau tso rau ntawm qhov tiaj tus, tiaj tus, qhib nto.
  2. Tig lub hwj chim.
  3. Saib koj cov neeg hlau kos duab plaub.

Yog tias koj tsis pom teeb ntawm lub microcontroller, rov qab mus thiab teeb meem teeb meem zoo li hauv Kauj Ruam 8.

Yog tias koj tus neeg hlau tsis txav mus, tshuaj xyuas ob zaug txuas lub zog rau tus neeg tsav tsheb darlington hauv Kauj Ruam 9.

Yog tias koj tus neeg hlau txav mus tsis raug, ob zaug kos tus pin txuas rau lub microcontroller thiab darlington tus tsav tsheb hauv Kauj Ruam 10.

Kauj ruam 15: Calibration

Calibration
Calibration
Calibration
Calibration
Calibration
Calibration
Calibration
Calibration

Yog tias koj tus neeg hlau txav mus rau thaj tsam kwv yees, nws yog lub sijhawm los muab qee daim ntawv tso thiab muab tus cwj mem tso rau hauv.

Ntsuas koj lub log txoj kab uas hla (Duab 1) thiab lub hauv paus log (Duab 2) hauv millimeters.

Koj qhov kev ntsuas ntsuas hauv cov cai yog:

ntab log_dia = 63; // hli (nce = muab kauv tawm)

ntab log_base = 109; // mm (nce = kauv hauv) int steps_rev = 128; // 128 rau 16x gearbox, 512 rau 64x gearbox

Kuv pib nrog ntsuas lub log txoj kab uas hla ntawm 65 hli thiab koj tuaj yeem pom cov thawv tig sab nraud lossis rov qab txhua lub sijhawm (Duab 3).

Thaum kawg kuv tuaj txog ntawm tus nqi 63mm (Duab 4). Koj tuaj yeem pom tias tseem muaj qee qhov yuam kev tshwm sim vim yog iav lash thiab zoo li no. Kaw kom txaus ua qee yam ntxim nyiam!

Kauj Ruam 16: Tsa thiab Nqis Tus Cwj Pwm

Tsa thiab Nqis Tus Cwj Pwm
Tsa thiab Nqis Tus Cwj Pwm
Tsa thiab Nqis Tus Cwj Pwm
Tsa thiab Nqis Tus Cwj Pwm

Peb tau ntxiv servo, tab sis tsis tau ua dab tsi nrog nws. Nws tso cai rau koj nce thiab txo tus cwj mem kom tus neeg hlau txav tau yam tsis tas yuav kos duab.

  1. Tso tus cwj mem dab tshos rau ntawm tus cwj mem (Duab 1).

    Yog tias nws xoob, xev nws rau hauv qhov chaw

  2. Txheeb xyuas tias nws yuav kov daim ntawv thaum lub caj npab servo qis dua.
  3. Txheeb xyuas tias nws yuav tsis kov daim ntawv thaum tsa.

Lub kaum sab xis servo tuaj yeem hloov kho los ntawm kev tshem lub tshuab raj thiab rov muab tso rau nws, lossis los ntawm software:

int PEN_DOWN = 20; // lub kaum sab xis ntawm servo thaum tus cwj mem poob qis

int PEN_UP = 80; // lub kaum sab xis ntawm servo thaum tus cwj mem nce

Cov lus txib cwj mem yog:

pab ();

pendown ();

Yog tias koj xav siv tus cwj mem sib txawv, koj yuav tsum hloov kho tus tuav cwj mem (www.thingiverse.com/thing:1052725) thiab dab tshos dab tshos (www.thingiverse.com/thing:1053273) nrog txoj kab uas hla raug.

Kauj Ruam 17: Muaj Kev Zoo Siab

Image
Image

Kuv vam tias koj tau ua rau qhov no tsis muaj ntau cov lus foom. Qhia rau kuv paub yam koj tau tawm tsam nrog yog li kuv tuaj yeem txhim kho cov lus qhia.

Tam sim no nws yog lub sijhawm los tshawb nrhiav. Yog tias koj saib cov ntawv xeem, koj yuav pom kuv tau muab qee tus qauv "Turtle" lus txib rau koj:

pem hauv ntej (nrug); // hli mm

rov qab (nrug); sab laug (kaum sab xis); // degrees sab xis (kaum sab xis); pab (); pendown (); ua (); // tso stepper kom txuag roj teeb

Siv cov lus txib no, koj yuav tsum muaj peev xwm ua tau ib yam dab tsi, los ntawm kev kos cov nplaim daus lossis sau koj lub npe. Yog tias koj xav tau kev pab pib, kos tawm:

  • https://code.org/learn
  • https://codecombat.com/

Kauj Ruam 18: Lwm Lub Sij Hawm

Lwm lub Platforms
Lwm lub Platforms

Puas yog tus neeg hlau no tuaj yeem ua tiav nrog?

Yog! Lub platform no hloov pauv tau yooj yim heev. Koj tsuas yog yuav tsum tau hloov kho lub chassis.

Kuv tau ua tiav nrog Raspberry Pi (Duab 1) thiab Adafruit Trinket (www.instructables.com/id/Low-Cost-Arduino-Compatible-Drawing-Robot/) (Duab 2).

Qhia rau kuv paub dab tsi koj tuaj nrog!

Pom zoo: