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0 Ohm Resistors — Parallax Forums

0 Ohm Resistors

sunblocksunblock Posts: 55
edited 2012-11-05 11:59 in General Discussion
I always look forward to the Mouser or Digikey deliveries from FedEx or UPS. Feel like an old man sitting in front of the tv spending like crazy on QVC or Ebay bids. But this time they sent me something I didn't order, several hundred 0 Ohm resistors. What in heck are these for? After reading on Al Gore's amazing internet I can only assume that they are the equivalent of a programmer's GOTO or JMP statements--considered lazy or bad form for us System Programmer/Analayst types. One find suggested using these on all circuit to GND connections. Be kind with the replies please, I am assuming there is a Homer Simpson, "Doh!" explaination for them.

Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2012-10-31 11:14
    They're usually used as jumpers when a board option seldom needs modification or to select among several functional variations of the same layout. In that capacity, they save money over headers and shunts.

    BTW, if DigiKey sends you something you didn't order, be sure to check that it wasn't accidentally substituted for something you did order, as sometimes happens.

    -Phil
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2012-10-31 11:29
    Ah ha! zero ohm resistor. That is a very rare three word oxymoron.

    If I say it fast 5 times, I feel like Zippy the Pinhead.

    BTW, if you make your own single sided printed circuit boards, they give the illusion that you designed the board with perfect routing. When I design with Eagle, using virtual zero ohm resistors actually helps the autorouter get things right.

    "When is a resistor not a resistor, Master?"
  • Martin_HMartin_H Posts: 4,051
    edited 2012-10-31 11:38
    I asked this a few months ago: http://forums.parallax.com/showthread.php?137554-What-is-the-point-of-zero-ohm-shunts
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2012-10-31 11:52
    Well they are not really resistors if you think about it. Language is weird. We dial telephones, but the dial is long gone. Many people have hot water heaters in their homes, but why would anyone want to heat hot water.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2012-10-31 11:57
    Loopy Byteloose wrote:
    Well they are not really resistors if you think about it.
    Really? When do they cease becoming resistors? 0.01 ohms? 0.001 ohms? 10-23 ohms? Zero is just the midpoint of a continuum that includes "negative-resistance" devices like tunnel diodes.

    -Phil
  • Invent-O-DocInvent-O-Doc Posts: 768
    edited 2012-10-31 12:03
    I never knew such a thing existed. Cool...
  • jazzedjazzed Posts: 11,803
    edited 2012-10-31 13:44
    Solder-blob pads are a nice alternative to zero-ohm resistors for DIY customizing. They would most likely incur a second operation in manufacturing (unless the PCB DRC rules are broken) where zero-ohm resistors would not.
  • jmgjmg Posts: 15,183
    edited 2012-10-31 14:21
    jazzed wrote: »
    Solder-blob pads are a nice alternative to zero-ohm resistors for DIY customizing. They would most likely incur a second operation in manufacturing (unless the PCB DRC rules are broken) where zero-ohm resistors would not.

    Zero ohm resistors can jump traces, which solder blobs find hard to do.
    Solder-blob are good for default-in-copper, and rare option-as-solder design choices.

    As well as Zero Ohm resistors, if you want to jumper a lot of traces, or even other components, there are also these :

    http://www.digikey.com/scripts/DkSearch/dksus.dll?vendor=0&keywords=S1621-46R
  • PliersPliers Posts: 280
    edited 2012-10-31 14:42
    Zero ohms at room temperature?
    Very impressive.
    Happy Halloween everybody.
  • Matt GillilandMatt Gilliland Posts: 1,406
    edited 2012-10-31 15:04
    Zero ohms at room temperature?
    Very impressive

    Marty! Where's my Flux Capacitor?

    but why would anyone want to heat hot water.
    It's amazing the things that haven't dawned on me yet.
    -MattG
  • jmgjmg Posts: 15,183
    edited 2012-10-31 15:36
    For those fixating on the 'zero' Wiki says this
    http://en.wikipedia.org/wiki/Zero-ohm_link
    only a maximum (typically 10–50 mΩ) is specified. so non-zero, and not quite defined enough to use as a shunt.
    For that, they want more money...

    and for a wry smile, I can buy a resistor (of course, not cheap)
    http://media.digikey.com/pdf/Data%20Sheets/Rohm%20PDFs/PMR10-SERIES.pdf
    that has a lower, and much more precise, resistance than a 'Zero Ohm' jumper :)
  • eldonb46eldonb46 Posts: 70
    edited 2012-10-31 15:55
    Actually, I found a interesting use for Zero Ohm resistors. During design, place them in series with the power pin of an IC with a decoupling cap (to ground) between the the Zero Ohm and the IC power pin, This make for easy PCB layout during design, the Caps do not get lost in a maze of similar caps in the initial PCB layout (or as it is know, the rats nest). Plus, the Zero Ohm resistors when not installed (or removed) can aid initial testing.
  • Mark_TMark_T Posts: 1,981
    edited 2012-10-31 16:05
    eldonb46 wrote: »
    Actually, I found a interesting use for Zero Ohm resistors. During design, place them in series with the power pin of an IC with a decoupling cap (to ground) between the the Zero Ohm and the IC power pin, This make for easy PCB layout during design, the Caps do not get lost in a maze of similar caps in the initial PCB layout (or as it is know, the rats nest). Plus, the Zero Ohm resistors when not installed (or removed) can aid initial testing.

    And you could actually substitute low value resistors if you wanted to be able to probe the current consumption of the chip, or an inductor to improve supply noise rejection...
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2012-10-31 16:06
    How do you even solder a 2 mOhm resistor and still get 2 mOhms in your circuit? 'Seems like it would depend on how much and what kind of solder and pad plating you use.

    -Phil
  • jmgjmg Posts: 15,183
    edited 2012-10-31 16:17
    Phil Pilgrim (PhiPi) wrote: »
    How do you even solder a 2 mOhm resistor and still get 2 mOhms in your circuit? 'Seems like it would depend on how much and what kind of solder and pad plating you use.

    Good question - the serious current sense resistors I've seen, are usually 4 terminal devices for that reason.
    ROhm claim to even have 1% variants on those, and guess you would route '4 terminal like', but that still leaves solder in the loop.
  • Clock LoopClock Loop Posts: 2,069
    edited 2012-11-01 08:46
    Phil Pilgrim (PhiPi) wrote: »
    Really? When do they cease becoming resistors? 0.01 ohms? 0.001 ohms? 10-23 ohms? Zero is just the midpoint of a continuum that includes "negative-resistance" devices like tunnel diodes.

    -Phil

    Now where did i put that -10 megohm resistor, I have a need to power a circuit using ambient heat......
    When are they going to come out with PELTIER resistors and components. Then we can just put a peltier resistor / inductor etc and have the circuit power....-its-self..... uhh.... move along.. you didn't just read that.

    I use 1 ohm resistors with 36 Luxeon Rebel leds, 1 ohm resistor inbetween each led. All in series powered by 120vac.,
    I also use HV rectifier diodes with better reverse voltage protection than the leds themselves.
    I also power the whole thing with a battery backup that has AVR. (automatic voltage regulation) Just incase any power line spikes. This array has no protection so I use a small cheap avr backup.
  • Heater.Heater. Posts: 21,230
    edited 2012-11-01 09:04
    Loopy,
    ...why would anyone want to heat hot water.
    Stay in a guest house or cheap hotel in England and you will soon find out why:)

    A good use for zero ohm resistors is that when you make a mistake on a board design you can substitute a zero ohm resistors for the incorrect component and continue manufacture without a board redesign. A famous case just now is on the Raspberry Pi board where zero ohm resistors are now used where two poly fuses used to be. It turned out the poly fuses were causing problems with supplying power to conected USB devices.
  • JLockeJLocke Posts: 354
    edited 2012-11-02 10:12
    Loopy Byteloose wrote: »
    Well they are not really resistors if you think about it. Language is weird. We dial telephones, but the dial is long gone. Many people have hot water heaters in their homes, but why would anyone want to heat hot water.

    Why do we drive on a parkway and park on a driveway?
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2012-11-02 10:32
    Heater. wrote: »
    Loopy,


    Stay in a guest house or cheap hotel in England and you will soon find out why:)

    A good use for zero ohm resistors is that when you make a mistake on a board design you can substitute a zero ohm resistors for the incorrect component and continue manufacture without a board redesign. A famous case just now is on the Raspberry Pi board where zero ohm resistors are now used where two poly fuses used to be. It turned out the poly fuses were causing problems with supplying power to conected USB devices.

    Polyfuses are very strange little devices in a world where everything is supposed to go faster and faster. They just crawl along and take their time recovering. Thank heavens for this resistor-like jumpers. But I still contend that something that has zero ohms is not a resistor, it is a conductor (maybe in drag).
  • jmgjmg Posts: 15,183
    edited 2012-11-02 12:12
    Loopy Byteloose wrote: »
    But I still contend that something that has zero ohms is not a resistor, it is a conductor (maybe in drag).

    These do not actually have zero ohms, but you can say that a part with poorly defined resistance, is not much use as a resistor. :)

    Reality is, you can buy parts (resistors) with lower milli-ohm values than the jumpers, and much more usable precisions.


    Some call 'Zero Ohm' parts jumpers, but they are often included as resistors as they have the same package and part codes.

    Here 'zero' is shorthand for 'Some Milli-Ohms, I don't really care how many'
  • wjsteelewjsteele Posts: 697
    edited 2012-11-05 11:59
    I dont' see it mentioned here, but a zero ohm resistor is a nice item to have for pick and place machines.
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