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Which way do you read a resistor?

Discussion in 'General Electronics Discussion' started by Pascal666, Sep 27, 2012.

  1. Pascal666

    Pascal666

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    Aug 20, 2012
    How do you know which side of a resistor is the one you start on? This one for example:
     

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    Last edited: Sep 27, 2012
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    On that 220 ohm 2% resistor? I'd start on the left. The two things that stick out is that the last red band is different to the other s(it's thinner) and 220 is a preferred value, 20000 isn't.

    If you measure it with a multimeter you should get 220 ohms or less.

    The good thing is that resistor colour codes rarely make sense when reversed. Those that do are often such wildly different values that it's not hard to test them.
     
  3. Pascal666

    Pascal666

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    Aug 20, 2012
    How are you getting 220 ohm 2% from brown brown black black red?
     
  4. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    It's not obvious that the color is brown. On my screen it looks definitely reddish, so I see red red black black red. Here is just one example for a color code calculator that gives the answer.

    If the color is brown, not red, the value is 110 Ohm 1%
     
  5. Pascal666

    Pascal666

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    Aug 20, 2012
    The picture gets bigger if you click on it.

    Comparing the left two stripes to the far right one, it appears to me the left two are brown and the far right is red.

    I decoded this as 110 Ohm 2%, a value different than what both of you have now said.
     
  6. davenn

    davenn Moderator

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    Sep 5, 2009
    but to repeat steve's question... Have you actually measured it yet ?

    Dave
     
  7. Pascal666

    Pascal666

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    Aug 20, 2012
    Yes, I took a multimeter to it yesterday. My question here is not the resistance, but how to know which side to start on when reading a resistor's color code. If I am reading it correctly, the codes on this one can indicate one of two possibilities:

    brown brown black black red gives 110 ohm 2%
    red black black brown brown gives 2k ohm 1%

    One of the above agrees with my multimeter, but had I not had a multimeter handy, is there a way I could have known or are resistor color codes simply ambiguous by nature?
     
  8. MrEE

    MrEE

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    Apr 13, 2012
    There will always be some ambiguity in color codes. Sometimes identifying the color can be a pain in the neck or should I say eyes. Red and brown are not always clear and can be confused with each other. The only thing identifying the tolerance ring in your resistor is the thickness of it. So just by looking at the picture I'd say it is a 110 ohm 2% resistor. Now if you had a large box with a bunch of resistors of every possible value and you are given the task of sorting them by their color code then good luck. Usually that is not the case. 99% of the time you expect a specific value or you are working with a circuit or a portion of a circuit and you just need to identify one out of a few. In this case the task becomes much simpler. As a last resort, just use a meter.
     
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    The same above applies to 110 Vs 2000 (It looks more red than brown to me, but it could be any combination of lighting, photo, monitor, and perception. It's easier when it's in front of you)

    If it measures 110 in circuit it doesn't mean it's a 110 ohm resistor either...

    If it measures 2k, then I'm surprised (and it also doesn't mean it's a 2k resistor)
     
  10. davenn

    davenn Moderator

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    Sep 5, 2009
    Metal film ( high tolerance 1 or 2%) resistors are notoriously difficult to read the colour codes with the red and brown being the main 2 colours that are VERY difficult to distinguish

    it really boils down to experience reading the colour shades used by different manufacturers and PHYSICALLY measuring it if in doubt
    As steve has pointed out the measurement will only fit reading the colour code reading it in one direction

    so the only way is to physically measure it

    In general carbon resistor colours are much more distinct, even between manufacturers

    Dave
     
  11. donkey

    donkey

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    Feb 26, 2011
    hey guys stupid question, if for example I had a burnt out resistor in a repair job and as stated the red and brown are hard to read, what would be the best way of figuring out the value to replace it?
    (that is if I can't find the schematic and the PCB had no values)
     
  12. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    It depends on how burnt the resistor is. If you can still read enough to be uncertain if the colours are red or brown, just measure it. It is unlikely to have shifted too far in resistance to get from 11xxx to 22xxx.

    If it's completely burnt, then you can't read the colours anyway, so you don't have this particular problem.
     
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