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I know the values of resistors if they are gold-colored at the end. When both ends are the same, such as brown-o-p-brown and red-x-y-z-red, I am in problems. How to know which side has the last colour and which side is the starting end?

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    \$\begingroup\$ Any reason not to empirically find the solution using test equipment such a multi-meter or DMM? \$\endgroup\$ – mctylr Jan 24 '11 at 2:55
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    \$\begingroup\$ @mctylr it could be that you are looking into a resistor soldered into a hard to reach place in a circuit board. \$\endgroup\$ – BuddhiP Nov 19 '15 at 6:40
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    \$\begingroup\$ @mctylr A good reason is that the resistor is blown, and there is no silk screen indication of its value. \$\endgroup\$ – Kaz Feb 13 '16 at 19:10
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I asked a similar question a long time ago here but the resistor chart which was mentioned there appears to have moved. So from its new home at itll.colorado.edu here's the diagram, as far as I can tell one band will be thicker signifying it as the tolerance band (no-one responded when I queried whether this was the case in the previous post above so if I'm wrong please let me know).

Resistor Chart

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    \$\begingroup\$ I usually test the resistor with small current and voltage let say 5V and 5A, depending on the voltage of course. Then, I calculate the resistance. Cannot trust thickness at all as guessed so many times wrong. \$\endgroup\$ – hhh Jun 5 '10 at 18:59
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    \$\begingroup\$ 5 A is a small current? o_O \$\endgroup\$ – endolith Jun 5 '10 at 22:19
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    \$\begingroup\$ When your entire goal is something exploding, i guess so. \$\endgroup\$ – Kortuk Jun 6 '10 at 18:46
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    \$\begingroup\$ @0x2A31 - I don't think the issue is the 5V, the 5A is a very high current for measuring resistors. That current will fry many resistors (or other components for that matter.) \$\endgroup\$ – bjarkef Jan 23 '11 at 12:22
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    \$\begingroup\$ You better may use a multimeter 0X2A31 to measure the resistance straight away. If the equipment you're using is capable of going to 0.1V (which sounds a lot to me), your multimeter is going to have a far greater accuracy in measuring. Especially if you know that current measurements on multimeters can be way off, and that multimeters have a considerable resistance as well. \$\endgroup\$ – Hans Jan 23 '11 at 22:05
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The starting point should be the band that is closest to one of the ends. The tolerance band is usually at the other end, on its own.

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If the start and end bands are ambiguous, you can usually work out which is probably the right way to read them by seeing which way round gives you a valid E24/E48/E96 etc. value.

..and there's always 'use a multimeter' to fall back on when you're still not sure.

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I am lazy with bad eye sight, I use my multimeter with some crocodile clips.

Then it goes in a baggie marked with the value.

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  • \$\begingroup\$ In my experience with 5-band 1/8 Watt blue colored (through hold) resistors, and any SMT resistors this is what I end up doing as a sanity check. \$\endgroup\$ – mctylr Jan 24 '11 at 2:53
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Amos provided the correct answer the time.

Since technology has evolved, I have found easier method: iPad. I use apps such as iCircuit, eTools lite and Ohm Work to find information fast for this kind of details.

When it is hard to say what the end is: use multimeter as instructed by mctylr.

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  • \$\begingroup\$ I think his username is Amos \$\endgroup\$ – abdullah kahraman Apr 3 '13 at 22:56
  • \$\begingroup\$ @abdullahkahraman sorry, typo, fixed. \$\endgroup\$ – hhh Apr 3 '13 at 23:15
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In theory there is supposed to be a larger gap between the value bands and the tolerance band.

In practice small components and sloppy printing often make this gap very hard to distinguish. Some of the colors can also be tricky to tell apart.

You can try reading it both ways, and see which of them makes more sense. For example brown-orange-violet--brown would be 130M 1% which is a standard value (though a very high one) while brown-violet-orange--brown would be 17K 1% which is not.

My general conclusion though is that trying to read color codes given no prior information is an excercise in frustration.

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