Difference between revisions of "Passives"

From OpenCircuits
Jump to navigation Jump to search
 
(29 intermediate revisions by 15 users not shown)
Line 1: Line 1:
[http://roconyng.forumvila.com/ paxil online] [http://bellasankey.myweb.io/flip-flop.html flip flop] [http://angelicrybicki.myweb.io/topic/converter-free.html converter free mmf mp3] [http://child.dynup.net/view/afra-behn.html afra behn] [http://utters.dynup.net/microsoft-photoshop.html microsoft photoshop] [http://musashmoto.qiye.in/wholesale-roses.html wholesale fresh roses] [http://vulgo.dynup.net/styles/white-printers.html white printers] [http://audiemuldoon.marte.ro/optivite.html optivite] [http://found.dynup.net/seasame-street.html .com seasame street] [http://ricardamontero.marte.ro/resources/bushwacker.html bed bushwacker cap] [http://moraforth.ifrance.com/description/imported-italian.html imported italian foods] [http://roxiegarfield.marte.ro/content/wing-tattoos.html picture of angel wing tattoo] [http://earthahohman.qiye.in/pages/kayla.html kayla] [http://lizzettesowards.qiye.in/wiki/veterinarian.html salary veterinarian] [http://roselinesteinbe.myweb.io/valve.html valve] [http://reaganroyals.wan.io/wiki/ghetto-cowboy.html ghetto cowboy] [http://sablaloc.freeweb7.com/new/festival-de-san.html festival de san remo] [http://isobelpenniman.wan.io/aortic-dissection.html aortic dissection] [http://astw56.datadiri.com/polk-county-sheriff.html polk county sheriff] [http://found.dynup.net/march-of-the-penguins.html march of the penguins] [http://roxiegarfield.marte.ro/content/jenna-jameson-clips.html clip jameson jenna lesbian] [http://propos.dynup.net/comments/rash-on-buttocks.html rash on buttocks] [http://monikacrepeau.datadiri.com/allison-krauss.html allison krauss] [http://vulgo.dynup.net/styles/embroidery-pattern.html embroidery free machine pattern] [http://propos.dynup.net/comments/fast-weight-loss.html fast weight loss diets] [http://twannafulks.ifrance.com/article/wood-working-projects.html wood working projects] [http://roxiegarfield.marte.ro/content/tweakui.html tweakui] [http://odiliaowensby.wan.io/burly-brawl.html burly brawl] [http://zellawillaims.ifrance.com/new/rick-perry.html rick perry] [http://moraforth.ifrance.com/description/nationalgeographiccom.html nationalgeographic.com railroad] [http://ricardamontero.marte.ro/resources/mutual-funds-analysis.html mutual funds analysis] [http://onitaransom.ifrance.com/article/couple-kissing.html kissing anime couple] [http://baentrek.freeweb7.com/description/dual-cf.html dual cf] [http://genovevahaney.marte.ro/tianna-lynn.html tianna lynn] [http://abbylongshore.datadiri.com/view/online-renters.html online renters insurance quote] [http://debwurth.ifrance.com/pages/racing-school.html andretti mario racing school] [http://lentus.dynup.net/pyrazine-synthesis.html pyrazine synthesis] [http://carlynbookout.marte.ro/small/david-banner.html david banner like a pimp] [http://tribes.dynup.net/blog/mobile-ultrasound.html mobile ultrasound business] [http://auroretolley.wan.io/freckles.html freckles] [http://emogenecuellar.ifrance.com/library/new-mexico-realtor.html association mexico new realtor] [http://earthahohman.qiye.in/pages/liveaid.html liveaid] [http://stern.dynup.net/text/tummy-tucks.html tummy tucks] [http://margerethanniga.datadiri.com/crack-cocain-chemical.html crack cocain chemical process] [http://elissajung.wan.io/blog/white-knight.html white knight] [http://albertgoulette.qiye.in/download-free.html download free full pc game] [http://carlynbookout.marte.ro/small/mazda-323.html mazda 323] [http://ameebelin.ifrance.com/roof-maintenance.html drain maintenance roof] [http://marcieloveland.ifrance.com/styles/ata-shipping-cases.html ata shipping cases] [http://antoninaloflin.datadiri.com/burning-man.html burning man] [http://brbess.freeweb7.com/articles/denzel-pump-up.html denzel pump up] [http://baentrek.freeweb7.com/description/foto-decapitazione.html foto decapitazione americano] [http://ricardamontero.marte.ro/resources/wolfs-rain-stray.html wolfs rain stray] [http://luellafinney.marte.ro/storm-bowling-ball.html storm bowling ball review] [http://stern.dynup.net/text/essay-leadership.html essay leadership woman] [http://extort.dynup.net/directory/shoe-covers.html shoes cover cheap] [http://lucitabarez.marte.ro/styles/mini-skirt.html mini-skirt] [http://utters.dynup.net/roadrunner.html road runner sports] [http://pinichol.freeweb7.com/lib/foto-torino.html foto torino] [http://marcieloveland.ifrance.com/styles/goldmember.html austin power goldmember] [http://pamuladonoghue.qiye.in/small/sell-gold-coins.html sell gold coins online] [http://jaynamcgruder.ecv.vg/q/shopkocom.html shopko.com] [http://lizzettesowards.qiye.in/wiki/database-services.html database service writing] [http://gatimber.forumvila.com/ tenuate online] [http://carlynbookout.marte.ro/small/keyword-texas-holdem.html keyword texas holdem] [http://rohazlet.forumvila.com/ buy zyban] [http://gobatten.forumvila.com/ cheap carisoprodol] [http://dorathyboldt.ifrance.com/power-inverter.html power inverter] [http://lentus.dynup.net/little-teen-petite.html little teen petite] [http://shonnathrush.ifrance.com/small/wake-forest.html wake forest] [http://vickeyparkhurst.qiye.in/pages/suave.html 13 calle lyric suave] [http://geslaven.freeweb7.com/directory/nuova-gissi-srl.html nuova gissi srl] [http://christabopp.wan.io/directory/chinese-pugs.html chinese pugs] [http://jolydian.freeweb7.com/blog/villa-zona-laghi.html villa zona laghi] [http://brbess.freeweb7.com/articles/cristina-milian.html cristina milian dip it low] [http://jocelynrieder.ifrance.com/table-top-displays.html table top display case] [http://ccono.freeweb7.com/library/gestion-du-mariage.html gestion du mariage 2.0] [http://zellawillaims.ifrance.com/new/englewood-florida.html englewood florida condominium] [http://ameebelin.ifrance.com/grocery-coupons.html coupon free grocery] [http://jene7777777.datadiri.com/library/quarterback-training.html quarterback training] [http://emogenecuellar.ifrance.com/library/formal-hair.html formal hair] [http://ricardamontero.marte.ro/resources/sonic-and-shadow.html sonic and shadow] [http://margerethanniga.datadiri.com/manifestation.html giant manifestation] [http://ricardamontero.marte.ro/resources/drug-rehab-center.html drug rehab center in texas] [http://elwandasais.marte.ro/cyclops.html cyclops light] [http://ameebelin.ifrance.com/predator-2.html predator 2] [http://isobelpenniman.wan.io/30th-birthday-party.html 30th birthday party ideas] [http://shonnathrush.ifrance.com/small/door-to-door-magazine.html door-to-door magazine sales crew] [http://jene7777777.datadiri.com/library/comic-party.html comic party game] [http://jene7777777.datadiri.com/library/epicure.html epicure] [http://christabopp.wan.io/directory/b-movies.html b movies] [http://onitaransom.ifrance.com/article/men-bulge.html men bulge] [http://pamuladonoghue.qiye.in/small/photodiode-array.html photodiode array] [http://baentrek.freeweb7.com/description/hp-portatile-pavillon.html hp portatile pavillon] [http://abbylongshore.datadiri.com/view/tortoises-for-sale.html tortoises for sale] [http://ccono.freeweb7.com/library/www-jerryleelewis.html www jerryleelewis com] [http://shirlharrill.ecv.vg/blog/online-pharmacy.html online pharmacy meds] [http://earthahohman.qiye.in/pages/phendimetrazine.html used metal shelving] [http://jalajuan.forumvila.com/ cheap levitra] [http://carmelduggan.ecv.vg/data/jpegs.html absolutly free jpegs xxx] [http://ricardamontero.marte.ro/resources/aerial-pictures.html live aerial picture] [http://lucreciamccollu.ifrance.com/college-of-the.html college of the canyons] [http://cufreder.forumvila.com/ flexeril online] [http://luellafinney.marte.ro/salt-body-scrubs.html body salt scrubs sea] [http://noellamarin.wan.io/investing-in-notes.html investing in notes and mortgages] [http://extort.dynup.net/directory/hairy-pussy-thumbnails.html hairy, pussy, thumbnails, free] [http://antoninaloflin.datadiri.com/ugo.html ugo] [http://audiemuldoon.marte.ro/rudi-bakhtiar.html bakhtiar rudi] [http://noellamarin.wan.io/video-tech-101.html video tech 101 free video by eddie batista] [http://marcieloveland.ifrance.com/styles/writing-for-government.html writing for government] [http://abbylongshore.datadiri.com/view/color-names.html crayola color name] [http://debwurth.ifrance.com/pages/pitchforkmedia.html pitchforkmedia] [http://odessachristens.marte.ro/crashing.html crashing] [http://ricardamontero.marte.ro/resources/sympathetic-nervous.html sympathetic nervous system] [http://dominqueraines.ifrance.com/description/alaskan-fishing.html alaskan fishing vacations] [http://bethanyyamamoto.myweb.io/big-busty-babes.html babe big boob busty] [http://eviebonet.myweb.io/blog/colombia.html colombia com] [http://baaisqui.forumvila.com/ diazepam online] [http://roseannecreasy.ifrance.com/q/ice-cream-makers.html ice cream makers] [http://tiannarummel.datadiri.com/tjmaxx.html tjmaxx] [http://astw56.datadiri.com/college-girl.html playboy college girl] [http://dominqueraines.ifrance.com/description/bec-cartright.html bec cartright] [http://jolydian.freeweb7.com/blog/vampyr-500.html vampyr 500] [http://brbess.freeweb7.com/articles/walker-una-storia.html walker una storia vera] [http://genovevahaney.marte.ro/washington-state.html washington state government] [http://vulgo.dynup.net/styles/full-figured.html full figured woman] [http://berryyeager.ecv.vg/q/gold-engagement.html diamond engagement gold ring yellow] [http://dorathyboldt.ifrance.com/veterinary.html veterinary hospital] [http://corrinwages.ifrance.com/natural-vitamins.html natural vitamins] [http://marivelescobedo.myweb.io/pokemon-card.html rare pokemon card] [http://tribes.dynup.net/blog/free-female.html free female orgasm movie clips] [http://luellafinney.marte.ro/soap-opera-digest.html soap opera digest] [http://emogenecuellar.ifrance.com/library/botox-new-york.html botox new york] [http://drewjurado.qiye.in/lib/lin.html lin] [http://child.dynup.net/view/pier-hotel-st-petersburg.html pier hotel st. petersburg florida] [http://carlynbookout.marte.ro/small/lawn-mowing.html lawn mowing] [http://pinichol.freeweb7.com/lib/simonov-konstantin.html simonov, konstantin] [http://vulgo.dynup.net/styles/luat-phap-thoat.html luat phap thoat vong] [http://carlynbookout.marte.ro/small/camusnagaul.html camusnagaul] [http://jocelynrieder.ifrance.com/vrml.html viewer vrml] [http://sablaloc.freeweb7.com/new/fabbrica-roller.html fabbrica roller team] [http://emogenecuellar.ifrance.com/library/download-movies.html download movies free] [http://baentrek.freeweb7.com/description/stempel.html stempel] [http://elwandasais.marte.ro/fossi.html fossi] [http://child.dynup.net/view/the-used-pics.html the used pic] [http://musashmoto.qiye.in/nsn.html nsn] [http://marivelescobedo.myweb.io/boost-i855-mobile.html boost i855 mobile] [http://carlynbookout.marte.ro/small/parole.html parole office] [http://wegillis.forumvila.com/ cheap phentermine] [http://shirlharrill.ecv.vg/blog/friedrich-air.html air cleaner friedrich] {{stub}}
+
{{stub}}
 +
 
 +
This article is being split into components check for duplication prior to updataing
 +
... I think it is pretty much dead and delinked.... now
 +
 
 
== Capacitors ==
 
== Capacitors ==
 
=== Basics ===
 
=== Basics ===
Line 35: Line 39:
 
# [http://www.northcountryradio.com/PDFs/column008.pdf RC Timers and Timing Circuits]
 
# [http://www.northcountryradio.com/PDFs/column008.pdf RC Timers and Timing Circuits]
 
# [http://en.wikipedia.org/wiki/Decoupling_capacitor Decoupling capacitor From Wikipedia, the free encyclopedia]
 
# [http://en.wikipedia.org/wiki/Decoupling_capacitor Decoupling capacitor From Wikipedia, the free encyclopedia]
 +
# [http://www.piclist.com/techref/caps.htm Components: Capacitors]
  
 
=== Electrolytic ===
 
=== Electrolytic ===
Line 59: Line 64:
  
 
== Inductors ==
 
== Inductors ==
 +
 +
An inductor reacts to current, but not to its value, but rather its change. It “tries” to keep the current through it constant. Any change in current causes a voltage across the inductor. The key equation for an inductor ( it is a bit complicated, but anyway here it ) is:
 +
 +
=== equation here soon ===
 +
 +
where
 +
L = inductance ( units: henry )
 +
V = voltage ( unit: volts )
 +
I = current ( unit: Ampere )
 +
t = time ( unit: seconds )
 +
 +
Uses:
 +
*tuned circuits: a circuit that responds in a special way to some frequencies( s ).
 +
*power supply filter: remove the pulsing DC left from rectification or other noise in the signal.
 +
*Decoupling: usually blocking high frequencies from one part of a circuit from getting in another part.
 +
*boost buck regulators: voltage regulators that decrease or increase voltage.
 +
 +
Links
 +
*[http://en.wikipedia.org/wiki/Inductors Inductor From Wikipedia, the free encyclopedia]
 +
 +
Comments:
 +
 
"Ferrites?  I don't know much about 'em, I only use ferrites in switching regulators."  --National Semiconductor's Bob Pease
 
"Ferrites?  I don't know much about 'em, I only use ferrites in switching regulators."  --National Semiconductor's Bob Pease
  
Line 64: Line 91:
  
 
== Resistors ==
 
== Resistors ==
 +
Probably the most basic component, just a hunk of wire ( low resistance ) or a long thin wire ( high resistance ).
 +
 +
 +
 +
When a voltage is applied to the two ends of an object, then a current usually flows through the object. If the object resists the voltage then the current will be small, if it does not then the current will be high. The amount of resistance is called ! The resistance. It is measured in ohms. ( Note that acting as a resistor is the simplest thing the object can do, there are more complicated behaviors, see capacitor, diodes, inductors, etc. A resistor is pretty much the simplest of electrical components.
 +
If almost no current flows we call the object an insulator, if a large current flows we call it a conductor. We often view a wire as a resistor of 0 ohms and an insulator as a resistor of infinite ohms. The key equation for a resistor is:
 +
 +
R=V/I
 +
 +
where I = current ( unit: amperes, amps )
 +
V = voltage ( unit: volts )
 +
R = resistance ( unit: ohms = volts per amp )
 +
 +
 +
 
List of standard 1% resistors.  If you want 1% resistors, you must pick from this list or you will pay a fortune for the resistor, assuming you can ever get it.
 
List of standard 1% resistors.  If you want 1% resistors, you must pick from this list or you will pay a fortune for the resistor, assuming you can ever get it.
 
Interpret these numbers as the "mantissa" of the value.   
 
Interpret these numbers as the "mantissa" of the value.   
Line 77: Line 119:
 
806 825 845 866 887  
 
806 825 845 866 887  
 
909 931 953 976
 
909 931 953 976
 +
 +
 +
 +
Uses
 +
*current limiting:
 +
Putting a resistor in a circuit, usually in series with another component it will reduce the current in the circuit, this is often useful to protect the other component. Very common to limit the current in a LED.
 +
current sense:
 +
When a resistor is in series with a circuit the voltage across it will vary with the current ( ohms law ) Sometimes we do this with a low value of resistance and use the voltage across the resistor to measure or control the current.
 +
*Isolation :
 +
A resistor between but connecting 2 components will tend to equalize their voltage, but only using small currents. It the components “want to go there own way, voltage wise” all they need do is put out a small current. For example people will sometimes ground themselves through a 10 mega ohm resistor. This tends to bring them to ground voltage, but they are protected from a deadly shock because most voltages cannot push a lethal current through 10 megs.
 +
*pull up or pull down:
 +
Sometimes a component will have a very high resistance to both the positive and negative side of the power supply and the voltage can easily drift around due to more or less random events. Under these conditions we will often connect a resistance ( typically around 10 K ohms ) to either the positive or negative side of the power supply. If to the positive side it is called a pull up resistor, if to the negative side a pull down resistor.
 +
*voltage divider:
 +
A voltage divider takes some voltage as an input and has an output that is some fraction of the input ( from 0 to 1 ) A volume control is usually some sort of voltage divider.
 +
 +
Links
 +
 +
#[http://www.piclist.com/techref/resistors.htm  Components: Resistors]
 +
#[http://en.wikipedia.org/wiki/Inductors Resistor From Wikipedia, the free encyclopedia]
 +
#[http://en.wikipedia.org/wiki/Pull_up_resistor Pull-up resistor From Wikipedia, the free encyclopedia]
 +
#[http://en.wikipedia.org/wiki/Voltage_divider Voltage divider rule From Wikipedia, the free encyclopedia]
 +
  
 
=== Carbon ===
 
=== Carbon ===
 +
The most common found resistor is the carbor film. Theses are generally the cheapest and most used in devices. The commonly are designed to withstand 1/8, 1/4, 1/2, and 1 watts of power.
 +
 
=== Metal Film ===
 
=== Metal Film ===
 
=== Wire-Wound ===
 
=== Wire-Wound ===
 +
Useful for cheap and accurate resistance, but has significant inductance compared to film resistors.  Some may be wound in one direction, others half in one direction half in the other, this second method reduces but does not entirely eliminate the inductance.  Very common in the range of 5 watts and up.  Beware of these for use.
 +
 
=== Precision ===
 
=== Precision ===
=== Potentiometers ===
+
 
[[Digital_Potentiometers]]
+
== Potentiometers ==
 +
 
 +
A Potentiometer is a resistor that has a third connection somewhere between the two main terminals. This connection is movable and if put at one end of the resistor will have no resistance between that end of the resistor and the full resistance to the other end. By moving the connection ( sometimes called a tap ) we can control the resistance to each end of the pot, but the sum of the two resistances always equals the total resistance of the potentiometer. A potentiometer is often used as a sort or adjustable voltage divider.
 +
There is an electriclly adjustable version: [[Digital_Potentiometers]]
 +
 
 +
 
 +
Uses
 +
*Adjustable voltage divider.
 +
*Volume control.
 +
*Variable resistor ( sometimes used when the correct value of resistance is not know or available, then the pot is use: it is adjusted, perhaps just once, after the circuit is built – to “tweak” the circuit into operating correctly.
 +
*Trim or 0 adjustment
 +
 
 +
External Links
 +
[http://en.wikipedia.org/wiki/Potentiometer Potentiometer From Wikipedia, the free encyclopedia( inc. Schematic and Picture )]
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
  
 
[[Category:Components]]
 
[[Category:Components]]

Latest revision as of 13:23, 28 January 2009

This article is being split into components check for duplication prior to updataing ... I think it is pretty much dead and delinked.... now

Capacitors[edit]

Basics[edit]

You can think of a capacitor as sort of a rechargeable battery, connect it to a voltage and a current will flow into it charging it up, later it will have a voltage of its own that can push the current back out. The key equation for a capacitor is:

c=q/v

Where:

  • C = capacitance ( units: farad = volts /coulomb )
  • V = voltage ( unit: volts )
  • Q = charge in the capacitor ( unit: coulomb )

A simple application of the formula above occurs when a constant or near constant current flow into a capacitor: then the voltage across it increases at a constant rate, the graph of the voltage against time will be a line rising ( or falling for a negative current ) from the left to the right. If the current is constant the line is straight.

Another way of thinking of a capacitor ( which is only partly correct ) is that it is a resistor with infinite resistance for DC and lower and lower resistance as the frequency goes up. This is a fair model for sinusoidal voltages and currents, but is less useful for signals such as square waves.


Uses:

  • ac coupling –- blocking -- isolation
  • timing
  • Time for a capacitor to charge or discharge is very roughly RC where R is the resistor in series with the capacitor.
  • Filter ( often power supply filter )
  • decoupling
  • tuned circuits

All capacitors are formed by having 2 conductors ( or plates ) connected to the two terminals of the capacitor. The conductors are separated from each other by insulator, typically very thin. Adding charge to one side forces like charge off the opposite plate because like charges repel. The larger the plates and the closer together they are the less voltage it takes to force in the charge. If the insulator ( called the dielectric ) is too thin it will be pierced by the charge and the capacitors becomes a conductor. Typically the basic specifications for a capacitors are its capacitance and the maximum voltage that can be used without causing the dialectic to break down.
There are many diferent technologies for manufacturing capacitor each with its own advantages and disadvantages.

External Links

  1. Capacitor From Wikipedia, the free encyclopedia
  2. RC circuit From Wikipedia, the free encyclopedia
  3. RC Timers and Timing Circuits
  4. Decoupling capacitor From Wikipedia, the free encyclopedia
  5. Components: Capacitors

Electrolytic[edit]

In electrolytic capacitors the insulating layer is formed by electro chemical action between the plates and other chemicals in the capacitor. This forms a very thin layer which allows large capacitance in a small package. Typically this works for one polarity and not another so electrolytic capacitors are marked with their polarity. There are some non-polarized electrolytics, but they are not common.

Some electrolytic capacitors manufactured between 1999 until today are made with bad electrolyte. Avoid these, see capacitor plague for more info.

Aluminum[edit]

Tantalum[edit]

Ceramic[edit]

Film[edit]

Polyester (Mylar)[edit]

Polystyrene[edit]

Polycarbonate[edit]

Polypropylene[edit]

Teflon[edit]

Exotics[edit]

Mica[edit]

Glass[edit]

Oil[edit]

Vacuum[edit]

Inductors[edit]

An inductor reacts to current, but not to its value, but rather its change. It “tries” to keep the current through it constant. Any change in current causes a voltage across the inductor. The key equation for an inductor ( it is a bit complicated, but anyway here it ) is:

equation here soon[edit]

where L = inductance ( units: henry ) V = voltage ( unit: volts ) I = current ( unit: Ampere ) t = time ( unit: seconds )

Uses:

  • tuned circuits: a circuit that responds in a special way to some frequencies( s ).
  • power supply filter: remove the pulsing DC left from rectification or other noise in the signal.
  • Decoupling: usually blocking high frequencies from one part of a circuit from getting in another part.
  • boost buck regulators: voltage regulators that decrease or increase voltage.

Links

Comments:

"Ferrites? I don't know much about 'em, I only use ferrites in switching regulators." --National Semiconductor's Bob Pease

Can be replaced in many circumstances with an impedance inverter using only an opamp, a capacitor, and a few resistors.

Resistors[edit]

Probably the most basic component, just a hunk of wire ( low resistance ) or a long thin wire ( high resistance ).


When a voltage is applied to the two ends of an object, then a current usually flows through the object. If the object resists the voltage then the current will be small, if it does not then the current will be high. The amount of resistance is called ! The resistance. It is measured in ohms. ( Note that acting as a resistor is the simplest thing the object can do, there are more complicated behaviors, see capacitor, diodes, inductors, etc. A resistor is pretty much the simplest of electrical components. If almost no current flows we call the object an insulator, if a large current flows we call it a conductor. We often view a wire as a resistor of 0 ohms and an insulator as a resistor of infinite ohms. The key equation for a resistor is:

R=V/I

where I = current ( unit: amperes, amps ) V = voltage ( unit: volts ) R = resistance ( unit: ohms = volts per amp )


List of standard 1% resistors. If you want 1% resistors, you must pick from this list or you will pay a fortune for the resistor, assuming you can ever get it. Interpret these numbers as the "mantissa" of the value. You can multiply the value by anything from 0.01 to about 100,000.

100 102 105 107 110 113 115 118 121 124 127 130 133 137 140 143 147 150 154 158 162 165 169 174 178 182 187 191 196 200 205 210 215 221 226 232 237 243 249 255 261 267 274 280 287 294 301 309 316 324 332 340 348 357 365 374 383 392 402 412 422 432 442 453 464 475 487 499 511 523 536 549 562 576 590 604 619 634 649 665 681 698 715 732 750 768 787 806 825 845 866 887 909 931 953 976


Uses

  • current limiting:

Putting a resistor in a circuit, usually in series with another component it will reduce the current in the circuit, this is often useful to protect the other component. Very common to limit the current in a LED. current sense: When a resistor is in series with a circuit the voltage across it will vary with the current ( ohms law ) Sometimes we do this with a low value of resistance and use the voltage across the resistor to measure or control the current.

  • Isolation :

A resistor between but connecting 2 components will tend to equalize their voltage, but only using small currents. It the components “want to go there own way, voltage wise” all they need do is put out a small current. For example people will sometimes ground themselves through a 10 mega ohm resistor. This tends to bring them to ground voltage, but they are protected from a deadly shock because most voltages cannot push a lethal current through 10 megs.

  • pull up or pull down:

Sometimes a component will have a very high resistance to both the positive and negative side of the power supply and the voltage can easily drift around due to more or less random events. Under these conditions we will often connect a resistance ( typically around 10 K ohms ) to either the positive or negative side of the power supply. If to the positive side it is called a pull up resistor, if to the negative side a pull down resistor.

  • voltage divider:

A voltage divider takes some voltage as an input and has an output that is some fraction of the input ( from 0 to 1 ) A volume control is usually some sort of voltage divider.

Links

  1. Components: Resistors
  2. Resistor From Wikipedia, the free encyclopedia
  3. Pull-up resistor From Wikipedia, the free encyclopedia
  4. Voltage divider rule From Wikipedia, the free encyclopedia


Carbon[edit]

The most common found resistor is the carbor film. Theses are generally the cheapest and most used in devices. The commonly are designed to withstand 1/8, 1/4, 1/2, and 1 watts of power.

Metal Film[edit]

Wire-Wound[edit]

Useful for cheap and accurate resistance, but has significant inductance compared to film resistors. Some may be wound in one direction, others half in one direction half in the other, this second method reduces but does not entirely eliminate the inductance. Very common in the range of 5 watts and up. Beware of these for use.

Precision[edit]

Potentiometers[edit]

A Potentiometer is a resistor that has a third connection somewhere between the two main terminals. This connection is movable and if put at one end of the resistor will have no resistance between that end of the resistor and the full resistance to the other end. By moving the connection ( sometimes called a tap ) we can control the resistance to each end of the pot, but the sum of the two resistances always equals the total resistance of the potentiometer. A potentiometer is often used as a sort or adjustable voltage divider. There is an electriclly adjustable version: Digital_Potentiometers


Uses

  • Adjustable voltage divider.
  • Volume control.
  • Variable resistor ( sometimes used when the correct value of resistance is not know or available, then the pot is use: it is adjusted, perhaps just once, after the circuit is built – to “tweak” the circuit into operating correctly.
  • Trim or 0 adjustment

External Links Potentiometer From Wikipedia, the free encyclopedia( inc. Schematic and Picture )