Tell me more ×
Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It's 100% free, no registration required.
up vote 8 down vote favorite
1

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?

share|improve this question
2  
Any reason not to empirically find the solution using test equipment such a multi-meter or DMM? – mctylr Jan 24 '11 at 2:55

5 Answers

up vote 15 down vote accepted

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

share|improve this answer
1  
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. – hhh Jun 5 '10 at 18:59
5  
5 A is a small current? o_O – endolith Jun 5 '10 at 22:19
When your entire goal is something exploding, i guess so. – Kortuk♦ Jun 6 '10 at 18:46
@endolith: well actually I start from the smallest unit of the equipment, usually 0.1V. If I cannot find the upper bound for the component, I gradually increase to some easy number such as 1V. Calculate V-I to get P. Chose 5V just because it is nice number but it can be a bit too high for testing, do not start with it, start small and then increase slowly to let component react. – hhh Jun 7 '10 at 20:57
@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.) – bjarkef Jan 23 '11 at 12:22
show 1 more comment
up vote 6 down vote

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.

share|improve this answer
up vote 3 down vote

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.

share|improve this answer
up vote 2 down vote

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.

share|improve this answer
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. – mctylr Jan 24 '11 at 2:53
up vote 0 down vote

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.

share|improve this answer
I think his username is Amos – abdullah kahraman Apr 3 at 22:56
@abdullahkahraman sorry, typo, fixed. – hhh Apr 3 at 23:15

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.