How to read a 5-band resistor that has its bands spread evenly?

[LegendPanda]

Hello, I just bought 165 resistors of different resistances and tolerances each having 5 bands. I was wondering how can I read a resistor that has all its bands spread evenly, ie. violet - green - black - red - brown? If you read them from left to right, you get 75k Ohms and 1% tolerance, what if I rotate the resistor by 180degrees and I have the bands from right to left?

Why can 4th band only be black, brown, red, orange, yellow, gold and silver while almost all bands have multipliers and 5th band only be brown, red, gold and silver while many other colours have tolerances as well? Violet for example has 0.1% tolerance, why can't it be on band 5?

Thank you.

 

[KrisBlueNZ]

Not all possible values exist, so with many of them, if you read the bands in the wrong direction, you'll get an impossible resistance, i.e. one that doesn't fall into the E24, E48, E96 or E192 series (whichever is appropriate according to the tolerance band).

For the example you gave, reading the bands backwards gives a resistance of 12 megohms, which is outside the range of standard resistors, so it's unlikely to be right. Especially at 0.1% tolerance! (Very high value resistors are difficult to make accurately.)

But to answer your question, start by using a multimeter to measure a few of them. If you think about the patterns that emerge while you're measuring them, you may figure out a trick you can use to work out which end is which without measuring any more of them (or maybe measure a few at random to check your trick is working reliably).

Check out a few web references on the resistor colour code. Some resistors have a band that indicates the temperature coefficient. But if all your resistors have five bands, and they're all modern components from standard resistor series, AFAIK you can assume that the bands will be digit, digit, digit, multiplier, tolerance. In one direction or the other.

If you have 165 resistors, all with different values, and several different tolerances, then I would say you have your work cut out for you

 

[Arouse1973]

If one of the end colours is anything other that Brown, Red, Gold or Silver. Then this is the start end. If both ends are Brown or Red then as Kris said work it out both ways, failing that measure them.
Thanks
Adam

 

[shrtrnd]

You can Google the resistor color code system, and find what you need. Different sites show a variety of charts.
I agree, some of the resistors I've seen with the five bands, are difficult to decipher sometimes.

 

[(*steve*)]

If you are aware of the preferred values, you will find there are very few that can be read both way.

My phone makes it hard to post links, so google for

Resistor Values E6 E12 E24 E48 E96 E192

And you will find a page on

www.logwell.com

Which has a chart of all the preferred values. If the resistors have 5 stripes then you either have 3 value bands, a multiplier band, and a tolerance band (where the tolerance band will give you the series -- 2% is E48) or very rarely 2 value bands, a multiplier, a tolerance, and a stability band. I say very rarely because they apparantly exist but I've never seen one

 

[shrtrnd]

I see a lot of them, *steve*. They're coming from no-name (alright, fly-by-night) Chinese manufacturers who I can't find information from (in English anyway).
Some of them actually omit the tolerance band. Others use two bands for the multiplier (adding a black band to substitute for one of the mulitplier digits.

 

[(*steve*)]

Really, you see many with the temperature coefficient (I said stability) band?

I've got to get out more (well, one of us does)

Also my link above lost half the URL so was pretty useless. Here it is in full: http://www.logwell.com/tech/components/resistor_values.html

When I go to this page I remember how my favorite electronics retailer of the day used to proclaim that they "now supplied 5% resistors as standard instead of 10%". But they still only stocked E12 values because that's all anyone ever used. *wow* 5% -- I wondered if I would ever see a 2% or even a 1% resistor!

 

[shrtrnd]

I think the guy whose making the ones I see, is doing it inside a tin shack in Shanghai.
Maybe nobody told him about industry standard rules.
To him, 'temperature coefficient' means summer or winter-time.
(whether or not the lead in the paint he's painting the digit bands with needs to be defrosted for use, or not)
(or how about: at what temperature the paint efficiently flows onto the resistor)

 

[davenn]

To him, 'temperature coefficient' means summer or winter-time.

hahaha that made me laugh

D