Basic Electricity...3. Circuits...9. Ohms Law Electrical Components Generating Voltage Types of Voltage...22

Transcription

1 Tabl of Contnts BASIC ELECTRICITY Subjct Pag...3 Circuits...9 Ohms Law...11 Elctrical Componnts...18 Gnrating Voltag...21 Typs of Voltag...22 Conductors, Insulators and SmiConductors...22 Diods...25 Variabl Rsistors...28 Common Circuit Dsignations...30 Rviw Qustions...31 Initial Print Dat: 5/01 Rvision Dat:

2 Modl: All Production Dat: All Objctivs Aftr complting this modul you should b abl to: Undrstand th thory of Elctron Flow vs Convntional Currnt Flow. Rcogniz th diffrnt typs of lctrical circuits. Prform Ohms law calculations. Rlat Ohms law to practical us in th workshop. Undrstand how diffrnt lctrical componnts oprat. Rcogniz circuit numbrs and abbrviations on ETM s. 2

3 Elctricity is dfind as th movmnt of lctrons from on atom to anothr. In ordr to undrstand lctricity a basic xplanation of th atom is ndd. All mattr is mad up of molculs. An atom is th smallst particl to which a molcul can b rducd. Nuclus Atoms consist of: Elctrons Ngativly chargd particls orbiting around a nuclus. Protons Positivly chargd particls in th nuclus. Nutrons Unchargd particls in th nuclus that stabiliz th protons. An atom is balancd or displays a nutral charg whn th numbr of protons and lctrons ar qual. Through various mans (.g. A chmical raction in th th automotiv battry) lctrons ar displacd from thir normal orbit. Ths displacd lctrons attach thmslvs to othr atoms, crating an unbalanc in th numbr of lctrons and protons in both atoms. Additional Elctron Protons Ngativ ion Nutrons Elctrons ps Protons Balancd ion Protons Positiv ion Missing Elctron Atoms which loos or rpl an lctron bcom positivly chargd bcaus of th gratr numbr of protons. Ths atoms ar calld Positiv Ions. Atoms which pickup or gain xtra lctrons bcom ngativly chargd and ar calld Ngativ Ions. Th ngativ ions will attmpt to rpl th xtra lctron and th positiv ions will attmpt to attract it. Nutrons Nutrons Elctrons ps Elctrons ps 3

4 Th movmnt of fr lctrons from on atom to anothr is calld lctron flow or lctric currnt flow. This flow of lctrons dos not man that a singl lctron travls th ntir lngth of th wir. Elctron flow is th movmnt of fr lctrons from atom to atom and th transmission of an lctrical impuls from on nd of a conductor to th othr. Th constant unbalancing and rbalancing of th atoms taks plac in lss than on millionth of a scond ps A singl strand of coppr wir contains billions of atoms Coppr Wir 4 Atoms Shown No Charg Applid To Wir ps Coppr Wir Positiv Charg 4 Elctron Flow 4 Atoms Shown Charg Applid To Wir Ngativ Charg ps

5 Elctromotiv Forc Friction, light, hat, prssur, chmical raction or magntic action ar all ways that lctrons ar frd. Th fr lctrons will mov away from th Elctron Moving Forc (EMF). A stram of fr lctrons form an lctrical currnt. EMF Mthod Automotiv Uss Friction Static, Walking Across Carpt Elctrostatic Fild, Capacitor Light Photolctric Cll, Light Controls Hadlamp and Mirror Snsors Prssur Pizolctric, Spakrs, Microphon Knock and Sid Impact Snsors Chmical Dry/Wt Cll Battris Primary Automotiv EMF, Battry Magntic Elctromagntic Induction, Coils Scondary Automotiv EMF, Gnrator Th battry and th gnrator ar th primary and scondary mans by which fr lctrons ar gnratd in automobils. Th chmical raction taking plac in th battry crats an Elctromotiv Forc (EMF) that provids us with th positiv ions and ngativ ions. Positiv Ions Ngativ Ions Th gnrator through magntic induction is our othr sourc of fr lctrons. (Positiv and ngativ ions) Th positiv ions collct at th positiv battry trminal and th ngativ ions collct at th ngativ battry trminal ps Th positiv and ngativ ions provid no nrgy unlss a path btwn thm is stablishd. This path is normally in th form of a load (.g. bulb, lctric motor or othr lctrical consumr) placd across th positiv and ngativ trminals of th battry ithr dirctly or through wirs. Fr lctrons ar pushd out of th battry ngativ trminal through a conductor to th positiv trminal. Positiv Ions Ngativ Ions ps 5

6 Whn a path is stablishd lctrons hav a rout from th ngativ trminal to th positiv trminal of th battry. That rout may tak th lctrons through wirs, motors, light bulbs or othr lctrical consumrs. Th mission of th lctrons is always to rturn to th sourc of thir nrgy which is th battry. Th movmnt of lctrons as discussd in th prcding pags is rfrrd to as th Thory of Elctron Flow. That is th actual path of th lctrons in an lctrical circuit, from ngativ to positiv. Positiv Ions Ngativ Ions Thory of Elctron Flow ps Bfor Scinc gav a glimps of th lctron, it was gnrally blivd that lctricity (lctrons) flowd from th positiv charg to th ngativ charg. Most lctrical symbols, wiring diagrams, and taching is basd on th Convntional Thory of Elctron Flow which stats that lctrons flow from positiv to ngativ. From this point on all rfrncs to currnt flow will b dfind by th Convntional Thory of Elctron Flow. Positiv Ions Ngativ Ions Convntional Thory of Elctron Flow ps Nots 6

7 Voltag Th potntial of th lctrons to flow is masurd in Volts. Voltag ps Think of voltag as prssur, th driving forc (prssur) pushing th lctrons from positiv to ngativ. On volt is th potntial diffrnc rquird to push on Amp of currnt through on Ohm of rsistanc. V Lss Ions Voltag is prsnt btwn two points whn a positiv charg xists at on point and a ngativ charg at th othr point. Th amount of voltag availabl is dpndnt on th numbr of ions at ach trminal of th battry ps V Lss Voltag Mor Ions Voltag Prcnt Thortical Currnt 12.6 Volts 100% 10 Amps 11.6 Volts 92% 9.2 Amps 11.0 Volts 87% 8.7 Amps 10.5 Volts 83% 8.3 Amps Maintaining propr voltag is important. As voltag drops,so dos th capacity for currnt flow ps Mor Voltag Voltag is th diffrnc in th potntial chargs btwn th positiv and ngativ trminals in a battry. If on volt is capabl of pushing x amount of currnt, two volts can push 2x, thr volts 3x and so on. 7

8 OFF Ampr Th unit of masur for currnt flow is th Ampr, commonly rfrrd to as Amps. Amps is th counting of lctrons flowing on a conductor past a givn point. On amp of currnt flow is qual to 6.23 billion billion (6.23 x ) lctrons moving past a point in on scond. ma ma V mv Hz mspulse SMOOTH TRIGGER DUTY ALERT % RPM H HOLD RANGE MAX MIN ZERO FLUKE 88 AUTOMOTIVE METER A RPM V A FUSED MAX 10A Amps Amps allow you to masur th volum of lctrical nrgy amprs flowing through a wir or lctrical consumr ps A ma COM V 1000 MAX Ohms Th Rsistanc of a circuit opposs currnt flow. Th unit of masur for rsistanc is th Ohm. On ohm is dfind as th amount of rsistanc that will allow on amp to flow whn bing pushd by on volt of prssur. Rsistanc slows th flow of currnt (rducs th numbr of lctrons flowing). Rsistanc changs lctrical nrgy into anothr form of nrgy (.g. hat, light or motion). Rsistanc rducs th numbr of lctrons flowing ps Elctrical Units of Masur Unit of Masur Symbol Basic Unit Volt V,U or E Volt V = volt = 1 volt mv = millivolt =.001 volt KV = Kilovolt = 1,000 volt Ampr Amp, A or I Amp A=amp=1 amp ma=milliamp =.001A KA=Kiloamp=1,000 A Ohm W Ohm 1W = 1ohm mw =milliohm=.001 ohm KW =Kiloohm = 1,000 ohm MW=Mgaohm=1,000,000 ohm 8

9 LEAD Circuits Elctricity must hav a complt or closd loop circuit to flow. A Circuit is dfind as an unbrokn, unintrruptd path which bgins and nds at th sam point. In th automobil that point is th battry. Th lctron flow must b from th battry through th wiring and consumrs back to th battry. That flow rprsnts a complt circuit. A typical circuit will contain: 1. A battry and/or gnrator systm (EMF or sourc of th lctrons) 2. Conductors (wiring to dlivr th lctrons to th consumrs) 3. Consumrs (th load bing placd on th systm) Any brak or intrruption in this circuit will caus th circuit to cas opration. Switch Switch Opn Circuit Complt/Closd Circuit DANGER / POISON RETURN RECYCLE DANGER / POISON RETURN LEAD RECYCLE Pb Pb SUFFICIENTL Y CHARGED INSUFFICIENTL Y CHARGED REPLACE TTERY BA SUFFICIENTL Y CHARGED INSUFFICIENTL Y CHARGED REPLACE TTERY BA ps Thr ar four basic typs of circuits: Sris Paralll Sris/Paralll Short Sris Circuit A Sris circuit provids on path for th currnt flow. That path is from th sourc of th currnt (th battry) through a conductor, consumr and back to th sourc. Sris Circuit Switch ps A Sris circuit provids constant currnt flow (amps) through th ntir circuit. Amps masurd in any two placs in th circuit will b qual ps 9

10 Paralll Circuit A Paralll circuit provids multipl currnt paths. In a Paralll circuit, all of th componnt s positiv trminals ar connctd to on point and all of th componnt s ngativ trminals ar connctd to a diffrnt common point. Sourc voltag is th sam at all loads. Th currnt flow in a paralll circuit will b qual to th sum of th currnt flowing through ach branch of th circuit. Switch SrisParalll Circuit ps A SrisParalll circuit contains portions of th currnt path that ar in sris with ach othr and othr portions of th path that ar paralll with ach othr. A hadlight circuit would typically b this typ of Sris/Paralll circuit. Th hadlight switch is in sris with th hadlights, and th hadlights ar in paralll branchs with ach othr. Switch ps Short Circuit Anothr typ of circuit found although not by dsign is th Short Circuit. Elctricity flows much lik watr undr prssur from th point of highst prssur to th point of lowst prssur. An unintndd path of currnt flow, such as a groundd conductor or consumr will provid th currnt flow a short path to hom, a short circuit. Short circuits allow unlimitd currnt flow, and with out th protction of a circuit brakr or fus will allow ovrloading of th conductor and possibl wir mltdown. 10 Short Circuit ps

11 Ohms Law Th ky to intllignt troublshooting of lctrical circuits is a thorough undrstanding of Ohms Law. Ohms Law stats that th currnt flowing in a circuit varis dirctly with th voltag and invrsly with th rsistanc. Th prssur of on volt applid to on Ohm of rsistanc will caus on amp of currnt to flow. If th voltag incrass, currnt will incras. If rsistanc incrass, currnt will dcras. Knowing any two of th thr factors (volts, rsistanc or currnt) nabls th third factor to b calculatd using Ohms Law. Th mathmatical xprssion is: Volts = Rsistanc X Currnt This formula is xprssd in th Ohms Law Triangl. To find a missing factor, insrt th known factors in th appropriat position and prform th math. A horizontal lin btwn two factors mans to divid, a vrtical lin mans multiply. V = Volts I = Currnt or Amps (A) R = Rsistanc (W) Not: Voltag is somtims xprssd as U or E. V I R ps Ohms Law Triangl Whil complt undrstanding of Ohms Law is ssntial in th diagnosis of lctrical problms, a practical undrstanding of how th thr factors affct ach othr is qually usful. Sourc voltag is not affctd by currnt or rsistanc. It can only hav thr stats. Too low Currnt flow will b low. Too high Currnt flow will also b too high. Corrct voltag Currnt flow will b dpndnt on th rsistanc. Currnt Flow will b dirctly affctd by ithr voltag or rsistanc. High voltag or low rsistanc will caus an incras in currnt flow. Low voltag or high rsistanc will caus a dcras in currnt flow. Rsistanc is not affctd by ithr voltag or currnt. Rsistanc lik sourc voltag can hav only thr stats. Too low currnt will b too high if th voltag is ok. Too high currnt flow will b low if th voltag is ok. Corrct rsistanc currnt flow will b high or low, dpndnt on voltag. 11

12 Ohms Law Sris Circuits Applying Ohms Law in a sris circuit is asy. Th currnt has only on path. Circuit rsistanc total is arrivd at by adding th individual rsistancs. Amprag is calculatd by dividing sourc voltag by th rsistanc total. R 1 R 2 = R t V/R t = A Ky Faturs Sris Circuit Currnt through ach load is th sam. Total rsistanc quals th sum of th individual rsistancs. Voltag drop across ach load will b diffrnt if th rsistanc is diffrnt. Total voltag drop quals sourc voltag. Sris Circuit Exampl: If R 1 =2W R 2 =2W Voltag = 12.0 volts What would th currnt b? ps = 4 (Rsistanc Total) R t = 4 12/4 = 3 Amps (I) Volts dividd by Rsistanc = Amps Expctd voltag drop at ach bulb? A x R 1 : A x R 2 3 x 2 = 6 volts W could xpct a voltag drop of 6 volts across ach bulb. I ps Ohms Law Paralll Circuit 2 Branchs Working in a Paralll circuit rquirs a littl mor math. Each branch of th circuit has it s own path to th voltag sourc. Bfor amps ar calculatd total circuit rsistanc must b found. In th diagram of th Paralll circuit both branchs hav sourc voltag availabl. Th voltag drop across ach branch will b th sam rgardlss of individual branch rsistanc. 12

13 Ky Faturs Paralll Circuit Switch Currnt flow through ach branch can b diffrnt if th rsistancs ar diffrnt. Total Rsistanc of th circuit is lss than th rsistanc of th lowst branch. DANGER / POISON RETURN LEAD RECYCLE Pb R R 1 2 Voltag drop across ach branch circuit is th sam. Total currnt is th sum of th branchs. SUFFICIENTL Y CHARGED INSUFFICIENTL Y CHARGED REPLACE TTERY BA ps Paralll Circuit Exampl: 13/1 If R 1 = 3W R 2 = 6W Voltag = 12.0 volts What would th currnt b for th R 1 branch? Th R 2 Branch? To find th total currnt draw (amps) in th circuit kp in mind that ach branch of th circuit could hav diffrnt rsistanc, so th currnt for ach branch could b diffrnt. (Exampl 13/1) 12/3 = 4 amps = R 1 branch currnt 12/6 = 2 amps = R 2 branch currnt What would th total circuit currnt b? 4 2 = 6 amps = Total circuit currnt To find th total rsistanc in th circuit indpndnt of voltag and amprag us ths formulas: Exampl: 13/2 If R 1 = 2W R 2 = 2W 2 = 1W 2 Paralll circuit with rsistancs that ar th sam on ach branch. Divid th rsistanc of on branch by th numbr of branchs (Exampl 13/2). Exampl: 13/3 If R 1 = 3W R 2 = 6W 3 x 6 = 18 = 2W Paralll circuit with rsistancs that ar diffrnt on ach branch (2 branchs) (Exampl 13/3). R 1 x R 2 R 1 R 2 13

14 Ohms Law Paralll Circuit mor than 2 Branchs Calculating circuit rsistanc in a Paralll circuit with mor than 2 branchs adds vn a littl mor math. R R = 3 4 All th ky faturs for a Paralll circuit still apply. R2 = R1 R2 R3 R Switch = Thr ar two mthods to calculat th total circuit rsistanc in a Paralll circuit of mor than 2 branchs. Th formulas ar: 1.92Ω = ps Exampl: 14/1 If R 1 = 3W R 2 = 3W R 3 = 6W R 4 = 4W = = = 12 = W Exampl: 14/2 If R 1 = 3W R 2 = 3W R 3 = 6W R 4 = 4W 3 x 3 = 9 = Thn, 1.5 x 6 = 9 = Thn, 1.2 x 4 = 4.8 = W 14 Basic lctricity

15 Ohms Law in SrisParalll circuit Whn calculating rsistanc in a srisparalll circuit, always calculat th quivalnt rsistanc in th paralll portion of th circuit. Thn add this rsistanc (quivalnt rsistanc) to th rsistanc of th sris portion of th circuit. Switch Ky Faturs SrisParalll Circuit Currnt in th sris portion of th circuit is th sam at any point of that portion. Total circuit rsistanc is th sum of th paralll branch quivalnt rsistanc and th sris portion rsistanc. Voltag applid to th paralll branch is sourc voltag minus any voltag drop across loads wird in sris to th paralll branch in front of it in th circuit ps Exampl: If R 1 = 4W R 2 = 6W R 3 = 2W Calculat th quivalnt rsistanc valu of R 1 and R 2. Rmmbr th rsistanc of a paralll circuit is lowr than th lowst rsistanc in that circuit. Th rsistanc of this portion of th circuit must b lowr than 4W, th lowst rsistanc. (4W X 6W)/(4W 6W) = 24/10 2.4W Equivalnt Rsistanc Now follow th ruls of a Sris circuit. Th total circuit rsistanc is qual to th sum of th individual rsistancs. 2.4W 2W = 4.4W Total rsistanc for this srisparalll circuit is 4.4 W Altrnat Formula for quivalnt rsistanc: Find th currnt draw of ach paralll branch, add togthr to gt th total currnt draw of th paralll portion, thn using ohms law find th rsistanc of th paralll branch. 12/R 1 = 3, 12/R 2 = = 5 12/5 = 2.4W 15

16 Worksht Calculat th missing valu using Ohms Law: Using th sris circuit. Switch 1. A = 2, V = 12, R = 2. R 1 = 4,R 2 = 4, V = 12, A = 3. R 1 = 4, R 2 = 2, A = 2, V = 4. V = 12, A = 6, R = 5. A = 3, R = 8, V = ps 6. R 1 =2, R 2 = 1, R 3 = 3, (Sris Circuit) V= 12, A= 7. What would th xpctd voltag drop b in Qustion 2? 8. What would th xpctd voltag drop b in Qustion 3? Using th Paralll circuit. Switch 9. R 1 = 2, R 2 = 1, R 3 = 2, R 4 = 1, R t = 10. Using R t from Qustion 9, V=12, A = 11.R 1 = 2, R 2 = 1, R 3 = 2, R 4 = 4, R t = 12. Using R t from Qustion 11, V =12, A = ps Using th SrisParalll Circuit. 13. R 1 = 2, R 2 = 4, R 3 = 2, R t = Switch 14. Using R t from Qustion 13, V =12, A = 15. Th rsistanc on th any branch of th paralll portion of this circuit is rducd. How is th total rsistanc for th circuit affctd? How is th amprag affctd? ps

17 Worksht Calculations 17

18 Elctrical Componnts Magntic Thory Th usfulnss of lctricity is gratly xpandd through magntism. Magntism nabls th xistnc of lctric motors, gnrators, coils, rlays, solnoid, transformrs, tc. Magntism, lik lctricity, can t b sn, wighd on a scal or masurd with a rulr. How it works and is put it to us can b undrstood. Two thoris xist to xplain how magnts work. Th first thory stats that a larg quantity of small magntizd particls xist in a magnt. If th itm is not magntizd th particls ar arrangd in a random ordr. Whn th itm bcoms magntizd th particls align with ach othr. Non Magntizd Iron Bar ps Th scond thory stats that whn th lctrons of atoms ar arrangd in a crtain ordr, th circls of forc of ach atom combin crating th magntism. Magntic Iron Bar Fundamntals of Magntism ps A magnt sts up a fild of forc. Magntic lins of forc form closd loops that flow from North to South. Th spac through which magntic lins of forc flow is calld th magntic fild. Th magntic fild is strongst closr to th magnt and bcoms wakr as it gts furthr away. Magntic lins of forc nvr cross ach othr. Thr is no known insulator against magntism. Magntic lins pass mor asily through iron and stl than air. Opposing forcs will occur at opposit nds of th magnt (Polarity). On nd is th North Pol (), th opposit nd is th South Pol (). Lik pols rpl ach othr, unlik pols attract ach othr. 18

19 Som matrials, wood cramics and som mtals, can not b magntizd. Fig.19/1 Thr ar two common typs of magnts: Prmannt Magnts mad from matrials such as hardnd stl that bcom magntic whn subjctd to an outsid magntizing forc and rmain magntic vn aftr th outsid forc has bn rmovd. N S Tmporary Magnts mad from matrials such as soft iron that rmain magntic only as long as an outsid magntic forc is prsnt. Th lins of forc of all magnts, ithr prmannt or tmporary flow from th North Pol of th magnt to th South Pol. Th magntic lins of forc or flux ar strongr closr to th magnt and gt wakr as th distanc from th magnt incrass. (Fig. 19/1) Polarity rfrs to th opposing forcs occurring at opposit nds of th magnt. All magnts hav a North Pol and a South Pol. Lik pols will rpl ach othr and unlik pols will attract. (Fig.19/2) Most tmporary magntic filds ar producd by lctricity flow. Whnvr currnt flows through a conductor magntic lins of forc dvlop around th conductor. Ths lins of forc form a circular pattrn. Th lins can b visualizd as a magntic cylindr xtnding th ntir lngth of th conductor. (Fig.19/3) Fig.19/2 Fig.19/3 N S S N N S N S Currnt Flow ps Th lins of forc hav dirction and chang dpndnt on dirction of currnt flow. Th dnsity of th lins of forc ar dpndnt on currnt flow through th conductor. Th gratr th currnt flow, th strongr th magntic fild that will b around th conductor. 19

20 Fig.20/1 Passing a currnt flow through a conductor will not gnrat a magntic fild strong nough to prform any work. If th conductor is coild, th lins of forc combin and bcom mor dns forming a strongr fild (Fig.20/1) jpg Th gratr th numbr of turns of th conductor or th strongr th currnt flowing through th conductor th th strongr th magntic fild. Insrting an iron cor in th coild conductor incrass th magntic fild vn mor as iron maks a bttr path for th magntic lins than air (Fig.20/2). This conductor wound around an iron bar is an Elctromagnt. A coil with an air cor is a Solnoid. Fig.20/ jpg Elctromagntic Induction Producing a magntic fild by flowing currnt through a conductor is a procss that can b rvrsd. A magntic fild can b st up that will caus currnt to flow in a conductor. This is calld inducing or gnrating lctricity by magntism. To induc voltag in a conductor it is ncssary to hav rlativ motion btwn th conductor and th magntic fild. This motion can b in any on of thr forms: Th conductor movs or rotats in a stationary magntic fild as in a DC Gnrator. Th magntic fild rotats in a stationary conductor producing voltag in th circuit as in an AC Gnrator or Altrnator. Th building or collapsing of a magntic fild across a stationary conductor, as in an Ignition Coil. 20

21 Gnrating Voltag Gnrator In a gnrator, th conductor movs through a stationary magntic fild inducing voltag at th commutator, which conncts to th circuit through brushs. Th voltag inducd is dirct currnt. Commutator jpg Altrnator In an altrnator th magntic fild movs (rotats) through th stationary conductor producing voltag in th circuit. Th voltag inducd is altrnating currnt jpg Ignition Coil Voltag can b inducd by th building or collapsing of a magntic fild across a stationary conductor. B powr is supplid by th battry and a magntic fild is st up around th coild conductor. Th DME grounds or pulls low th currnt from th conductor and th loss of currnt causs th magntic fild to collaps inducing voltag in th scondary conductor ps 21

22 Typs of Voltag Print Chang End Srvics BMW Masuring Systm Oscilloscop Display Hlp DC Voltag A flow of currnt that movs continuously in on dirction from a point of high potntial to a point of low potntial is rfrrd to as DC (Dirct Currnt). A MV Cursor1 Mmory Cursor2 BVmV T R I 8 80 G G 4 40 E 0 0 R L 4 40 E 8 80 V E L Holdscrn ChannlB Zoom Amplitud ChannlA Amplitud ChannlB Timvalu Most automotiv circuits oprat on DC voltag as supplid by th battry(s). AC Voltag ps Multimtr Countr OscilloscopStimulatorsPrst stting Maurmnts Print Chang End Srvics BMW Masuring Systm Oscilloscop Display Stimulat Hlp Currnt which rvrss its dirction at rgular intrvals is calld AC (Altrnating Currnt). This rgular and continuous rvrsal of currnt flow (cycl) occurs many tims pr scond. AC voltag as producd by an automotiv altrnator must b changd to dirct currnt so that th battry can b chargd. A MV Cursor1 Mmory Cursor BVmV T R I 8 80 G G 4 40 E 0 0 R L 4 40 E 8 80 V E L Holdscrn ChannlB Zoom Amplitud ChannlA Amplitud ChannlB Timvalu Stimulat Conductors, Insulators and SmiConductors ps Multimtr Countr OscilloscopStimulatorsPrst stting Maurmnts Elctrical proprtis of various matrials ar dtrmind by th numbr of lctrons in th outr ring of thir atoms. Conductors Matrials with 13 lctrons in th atoms outr ring mak it asy for lctrons to mov from atom to atom. Rmmbr that th dfinition of currnt flow is th movmnt of fr lctrons Conductor from on atom to anothr. Th lctrons in th outr ring of ths conductors ar loosly hld and vn a low EMF will caus th flow of fr lctrons. Many mtals ar good conductors, spcially gold, silvr, coppr, and aluminum. But not all conductors hav th sam amount of rsistanc to th flow of fr lctrons ps 22

23 Insulators Matrials with 58 lctrons in thir outr ring hav thos lctrons bound tightly. Ths matrials ar insulators (Poor conductors). Th lctrons in th outr rings rsist movmnt, th atoms don t giv up th lctrons asily or accpt fr lctrons asily. This ffctivly stops th flow of fr lctrons and thus any lctrical currnt. Rubbr, glass, and crtain plastics ar xampls of good insulators. Insulators ar usd in circuits to insur that th flow of lctrons stays in th conductor and can b dirctd to th propr plac in th systm. Insulator ps SmiConductors Matrials with xactly 4 lctrons in th atoms outr ring ar nithr conductors nor insulators. Th 4 lctrons in th outr ring caus spcial lctrical proprtis which giv thm th nam SmiConductor. Matrials such as Grmanium and Silicon ar ar two widly usd smiconductors. Smiconductor ps SmiConductor Doping Whn smiconductors ar in th form of a crystal, th four lctrons of th outr ring ar shard with a nighboring atom. This maks th crystal form of ths matrials an xcllnt insulator bcaus thr ar no fr lctrons to carry a currnt flow. Smiconductor Insulator ps 23

24 Othr lmnts (Impuritis) can b addd to chang th crystallin structur of th Grmanium and Silicon. This is calld Doping of th smiconductors. Doping crats fr lctrons or hols nabling th smiconductor to carry currnt. NTyp Matrial Fr Elctrons If th smiconductor is dopd with an lmnt having 5 lctrons in its outr ring thr will not b nough spac in th outr ring for th 9th lctron (4 lctrons in th smiconductor and 5 in th impurity). This typ of dopd matrial is calld ngativ or Nmatrial, bcaus it alrady has xcss lctrons and will rpl additional n g a t i v chargs. N Matrial ps PTyp Matrial If th smiconductor is dopd with an lmnt having 3 lctrons in its outr ring som of th atoms will only hav 7 lctrons in th outr ring. Thr will b a hol in som of th outr rings. This typ of dopd matrial is calld positiv or Pmatrial bcaus it will attract fr lctrons Hols Junctions PMatrial Doping Grmanium and Silicon caus thm to bhav in unusual but prdictabl ways whn xposd to voltag, dpnding on which charg of th voltag is connctd to which typ of matrial (P or N). Th lin along which joind P and N matrial mt is calld th Junction. A simpl componnt consisting of Pmatrial and Nmatrial joind at a junction is calld a diod. Th application of voltag to th two dopd smiconductor matrials is calld biasing. A mor complx matrial containing two PN junctions is calld a Transistor ps 24

25 Diod Whn N and Ptyp smiconductor matrials ar joind togthr to form a singl crystal a Diod is cratd. Th diod allows lctron flow in on dirction only. PN Junction A diod has a forward bias whn th Anod (Pmatrial) is connctd to B and th Cathod (Nmatrial) is connctd to B. Rvrsing th sourc voltag on th diod will rsult in currnt flow stoppag. This is calld rvrs bias. Anod P N Cathod Diods ar ratd for spcific voltag and currnt flow. Th diod can not withstand unlimitd forward bias and currnt flow ps Znr Diod A diod which will allow a spcifid amount of rvrs flow currnt is calld a Znr Diod. If th brakdown voltag of th znr diod is 6 volts, at 6 volts and abov th znr diod will allow rvrs currnt flow with no damag to th diod. Blow th brakdown voltag th znr diod will function as a normal diod and allow currnt flow in only on dirction. Znr diods ar oftn usd in charging systms to rctify or convrt AC currnt to DC. Lik th diod, znr diods ar ratd for spcific voltag, currnt and rvrs currnt. Light Emitting Diod LightEmitting Diods (LED) mit visibl light whn forward biasd. As currnt flows through th diod, lctrical nrgy is convrtd into visibl light that is radiatd through th thin positiv matrial layr in th diod. 25

26 Currnt Currnt Transistors Collctor Th Transistor is a diod with som additional smiconductor matrial. Th transistor contains two PN junctions, compard to on in a diod. Bas Transistors can b constructd in two ways: th P sction can b sandwichd btwn two N sctions forming a NPN transistor, or th N sction sandwichd btwn two P sctions forming a PNP transistor. NPN Transistor NPN Transistor Emittr Th thr sctions of th transistor ar calld th Emittr, th Bas and th Collctor ps Currnt applid to th bas will flow through th transistor. Currnt flows through th NPN in on dirction and through th PNP in th opposit dirction. Bas Collctor Transistors ar usd to control currnt flow, act as a switch or as an amplifir to vary th currnt output dpndnt on bas voltag variations. A transistor allows control of larg currnts with small currnt signals. PNP Transistor PNP Transistor Emittr ps Rlays A Rlay is a switch that uss lctromagntism to physically mov th contacts A small of amount of currnt flow through a rlay coil movs an armatur and opns or closs a st of points Th points control th flow of a largr amount of currnt through a sparat circuit ps 26

27 SUFFICIENTL Y CHARGED INSUFFICIENTL Y CHARGED REPLACE TTERY BA Pb DANGER / POISON RECYCLE Think of th two sids of a rlay indpndntly. Control sid: Which includs th B (KL86) and B (KL85) for th coil that crats th magntic forc. If this sid of th rlay fails opn th work sid points will rmain in thir at rst position. Work sid: Which includs th B input powr (KL30) and th Rlay output (KL87). Failur of this sid of th rlay in th closd position (sticking points) will rsult in constant currnt flow. BMW uss rlays with various numbrs of pins (3,4,5 pin) and pin configurations (normally opn, normally closd and changovr typ). Do not substitut rlays. Always rplac with th sam typ (.g. DME Main Powr Rlay, Scondary Air Pump Rlay and Rar Window Dfrostr Rlay.). Rfr to ETM Solnoids A Solnoid, lik a rlay, uss currnt flow and lctromagntism to produc mchanical movmnt. Solnoids consist of a coil winding around a spring loadd mtallic plungr. Cor (Armatur) Solnoid Contacts Coil Whn currnt flows through th winding, th magntic fild attracts th movabl plungr, pulling it against spring prssur into th cntr of th coil. Whn currnt flow stops, th magntic fild collapss and th plungr is movd out of th coil by spring prssur. Powr Sourc LEAD RETURN Switch Startr Motor Solnoids ar commonly usd in startr motors, injctors and purg valvs. Switchs A Switch is a mchanical dvic usd to start, stop or rdirct currnt flow. A switch can b installd on th positiv sid of th circuit or th ngativ sid of th circuit. A switch can b usd to to control a load dvic dirctly or usd to oprat a rlay which in turn can oprat a highr currnt dvic. (.g. Hadlight switch, Horn button and Window switch.) Rsistors Rsistors limit th currnt flow in a circuit. Th rsistor is usd in a circuit to introduc a dsird amount of rsistanc into th circuit. Rsistors ar availabl in fixd rsistanc or variabl rsistanc. Fixd rsistors ar color codd to indicat thir rsistanc. 27

28 Rsistor color Cod Guid ps Variabl Rsistors Thrmistor Th rsistanc of matrials can vary with changs in tmpratur; thrfor, rsistors can hav a changing rsistanc valu dpndnt on tmpratur. A Thrmistor is a rsistor that can achiv larg changs in rsistanc with small changs in Engin Tmp Dual Thrmistor tmpratur. Thrmistors ar normally of th NTC (ngativ tmpratur cofficint) typ. As th tmpratur incrass th rsistanc dcrass. BMW also uss PTC (positiv tmpratur cofficint) typ thrmistors. In a PTC th rsistanc incrass as th tmpratur incrass jpg

29 ps Potntiomtr A Potntiomtr (pot.) is a variabl rsistor capabl of changing rsistanc valus. Potntiomtrs hav thr trminals. On of th trminals is supply voltag, usually 5 volts. On of th trminals is th control modul ground, and th third trminal is for th input signal into th control modul. (Output from th Pot.) Potntiomtrs ar usd to masur mchanical movmnt. (.g. Van air flow mtrs, Throttl position snsors and Pdal position snsors.) ps Rhostat A Rhostat is similar in opration to a potntiomtr xcpt a Rhostat only has two connctors. This arrangmnt allows th rsistanc to b varid btwn thos two connctors. Elctric Motors DC motors ar similar to DC gnrators. Thy may b dscribd as gnrators run backwards. Whn currnt is passd through th armatur of a DC motor, a torqu is gnratd by magntic raction and th armatur rvolvs. Stppr Motors Stppr Motors bhav diffrntly than standard DC motors. Unlik DC motors which spin frly whn powr is applid, stppr motors do as thir nam suggsts, thy stp or rotat incrmntally a littl bit at a tim. Whil DC motors nd highr spds to produc highr torqu, stppr motors provid thir highst torqu at thir slowst spds. Stppr motors also hav holding torqu, th ability to rsist movmnt by outsid forcs. Stpprs ar drivn by th intraction (attraction and rpulsion) of magntic filds. Th driving magntic fild rotats as stratgically placd coils ar switchd on and off. This pushs and pulls at prmannt magnts arrangd around th rotor that driv th output shaft. 29

30 Common Circuit Dsignations NAME CIRCUIT B Battry Positiv B Battry Ngativ KL Standardizd Abbrviation for Clamp or Trminal Numbr KLO Ignition Switch Off KLR Voltag Ignition Switch in ACC, Run Start Hot in Acc/ Run/ Start KL15 Voltag Ignition Switch in Run and Start Hot (12v) in Run/ Start KL15U/15i Voltag Ignition Switch in Run Hot (12v) in Run KL30 12v At All Tims (Rlay Work Powr) Hot (12v) All Tims KL30H Startr Signal to ZKE KL50 Voltag Ignition Switch in Start Hot (12v) in Start KL58 Intrior Lighting Dimmr Signal KL61 Ground with Altrnator Output, 12v with KL15 85 Rlay Coil Ground (Signal) control sid 86 Rlay Coil B Control Sid 87 Rlay Output Work Sid 87a Rlay Output Work Sid At Rst 30

31 Rviw Qustions 1. Elctrons orbit around a nuclus of what matrials? 2. Why ar som atoms rfrrd to Ngativ Ions and whr to do thy collct? 3. Whr do th fr lctrons com from and how ar thy frd? 4. Dscrib th flow of lctrons using th Thory of Elctron Flow 5. An incras in th numbr of ngativ ions collcting at th ngativ battry post will hav what ffct on th potntial of lctrons to flow? 6. Nam thr things a complt circuit will contain? 7. Dscrib how currnt flow will b affctd by voltag and/or rsistanc. 8. What affct will incrasing currnt flow hav on th magntic fild around a conductor? 9. Nam th thr forms of motion usd to induc voltag in a conductor. 10.What will happn to currnt, if a diod is installd in a forward bias? 11. What happns to th rsistanc of an NTC typ variabl rsistor if th tmpratur is dcrasd? 12. What typ of motor can b usd to hold somthing still? 13. What is Doping of smiconductors? 14. Why can t lctrons mov about frly in an insulator? 31