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I've been using the Arduino starter kit recently, and for a project I require a 10 thousand ohm resistor. The kit comes with a belt of different resistors, and It has some 10k resistors but I've been having some trouble reading the color code on the resistors, I know the color values and the rules for 4 and 5 band resistors.

The main issue is that I don't always know which direction to read the resistors, I know its left to right but I don't know the indicators of the left and right sides. My friend said it doesn't matter but I know this isn't true in this example of a 5 band 220 ohm resistor

  • The correct way: "red, red, black, black, brown"
  • The incorrect way: "brown, black, black, red, red"

I do suspect one 5 band resistor, because it reads "brown, black, black, red, brown", I know the last band is wrong but I feel like that could be the way gold shows up on a blue resistor.

Dmitry Grigoryev
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Cipher Visor
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    If it's a 220 ohm resistor and you read 1, 0, 2, 2, then you have it backwards. – The Photon Jul 22 '19 at 04:39
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    Use an ohmmeter to measure the value if you suspect you are reading the colour code incorrectly. – Peter Bennett Jul 22 '19 at 04:52
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    Do I sense a project ? .. A project to make an ohmmeter from the Arduino ;) ? But yeah, use a multi meter, much easier.. Edit: Speaking of the sun .. http://www.circuitbasics.com/arduino-ohm-meter/ – Sorenp Jul 22 '19 at 05:22
  • http://www.circuitbasics.com/arduino-ohm-meter/ – Daniel K Jul 22 '19 at 05:23
  • Similar question: https://electronics.stackexchange.com/questions/117974/5-band-resistors-and-correct-orientation – Daniel K Jul 22 '19 at 05:26
  • I would use a separate current source for a Arduino based ohm meter. A LM317 based CC source would be cheap insurance and allow you to meter into the milliohm range as an added bonus. – GB - AE7OO Jul 22 '19 at 05:27
  • look for a "silver" band. That is likely the TOLERANCE band. Then start at the other end. – analogsystemsrf Jul 22 '19 at 07:05

3 Answers3

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The tolerance band (last band) is usually either a litter thicker or spaced a little wider separation away from the first 4 bands. If they are all equal, then the whole group of 5 bands would be shifted to one side of the resister (shifted towards starting digit side).

Edmond
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Normally there will be separation between groups. Do a search on 5 band resistor images.

Meaning that you'll see a group of 4 and then with a wider separation a single band.

I've seen some older mil-spec flame proof resistors which have 5 equal bands. In that case you have to use a combination of experience and your (milli)ohm meter to determine value.

I have also seen mil-spec axial capacitors which have 5 equally spaced bands. Again your ohm meter is your friend.

If you don't have a milliohm meter(and you've got resistors with that pesky silver/gold 4th band), adapters are easier to make.
A search of "milliohm meter adapter" comes back with plenty of DIY adapters to choose from.

GB - AE7OO
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Some resistors can be quite ambiguous. Now is the time to buy a cheap DMM to measure them to check. They're useful for other things as well. You'll soon wonder how you managed without one.

Neil_UK
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