Why do resistors still use color coding?

Question

I always wondered why color coding is still used on resistors in 2014.

Here is Wikipedia's word on the original reason why :

Colorbands were commonly used (especially on resistors) because they were easily printed on tiny components, decreasing construction costs. However, there were drawbacks, especially for color blind people. Overheating of a component, or dirt accumulation, may make it impossible to distinguish brown from red from orange. Advances in printing technology have made printed numbers practical for small components, which are often found in modern electronics.

However, like pointed out in this quote, printing small numbers on electronic is now quite an easy thing (or so it seems) and it would, in my opinion, be much more convenient, especially for colour-blind people.

Is there reason why we still use colour coding on resistors in 2014?

Answer 1

My opinion.

Through hole parts are often cylindrical. Hence applying stripes is simple in production. Resistors may have five stripes, tolerance, 3 significant digits, and order of magnitude. That is a lot of information to write, "22811" 22.8ohm 1%? In san-serif font what is 88818? It would be possible to read 1, 2 or 5, 6 or 9, and 8 rotated, i.e. upside down, and be confused.

As pointed out by JRE, a letter in the text is used to help ensure the text is the correct way round, e.g. 22K8.

However, while colour blindness is a problem for stripes, dyslexia is for text. I know of people who would write 'k' backwards without noticing.

Edit: There are many written languages which do not use the Arabic digits (in fact, Arabic digits is a misnomer, because the Arabic digits are different shape or value to commonly recognised digits in 'the west'). So printing digits isn't automatically better than a level of indirection via colour which is language independent.

One pretty thing about 7 of the resistor colour codes is it is in the same sequence as the colours of the rainbow (in some cultures), so many people learn that part of the sequence as children.

The through hole cylindrical part could have its wires bent in any direction, and coloured stripes are still legible from any direction.

If written text is applied in only one location, the part value may be obscured or invisible when it is in circuit. That would be a disaster for repair and inspection.

Hence, written text will have to be applied on all sides in order to be legible, which may well be more difficult and hence expensive to produce, and still awkward to read. Stripes don't suffer from this orientation problem. Stripes are simple to use.

Manufacturers have already invested in machinery to product components with colour stripes.

Where is the competitive advantage? There needs to be 'new' money to fund the change over to printed numbers, or it won't happen. I don't see anyone financial benefit.

I haven't seen any new robots doing pick & place with through hole parts. It is hard to imagine such a robot would have enough financial advantage over SMT to make it worthwhile.

The assembly staff who use the components will have to be retrained, and what benefit does the assembly company get?

Through-hole with printed numbers would have to show big benefits to replace coloured rings. AFAIK, SMT has displaced through-hole in the majority of products; robots are cheaper than labour costs humans for mass production.

"Show me the money" - It seems a very tenuous benefit to printing numbers vs lots of cost, especially when the investment has been made already, in a shrinking sector of industry.

Answer 2

The reason for using color bands on through-hole (axial) resistors is simple -- when they are inserted into the PCB, you can't guarantee their orientation -- there is no top or bottom. So you need a way to mark the value so it can be seen no matter how the part is oriented with the board. Color bands are perfect for this.

For this reason, I don't expect to see color bands disappearing from through-hole resistors.

With surface mount parts, there is a top and bottom, so the parts can have the value stamped on the top.

Answer 3

My guess (and it is just that) - colour bands are easy to apply with a basic machine (rollers dipped in paint, component rolls past) and if the machine works, why change it?

The alphanumeric markings on things like SMD devices require laser-etching, printing or similar. I'd further guess that either the laser etching / printing is already an inherent part of the production of SMD components, or that it's easier than trying to colour band or print or whatever onto a flat/square component, or that when they developed the production system they decided it was no great extra effort to move from colour bands to alphanumerics.

TBH most components used, by bulk sales, will be fed in reels into a pick & place machine, as long as the label on the reel or package is correct the machine is not reading colour codes or part numbers.

Answer 4

TRADITION. Nothing else.

Maybe the banding technology is older and cheaper than alphanumeric etching technology (and in some alphanumeric-coded capacitors and resistors where the value is printed with a blackish-ink, and NOT etched), the if the ink of 1 character got erased some-how, the small parts becomes almost unusable.

But if once the modern etching methods get popularized, it will no longer remain so-costly.

Color-codes are quite useful in identifying Qualitative informations (Live-wire, Neutral-Wire etc), but they're indeed not good to encode a quantitative value.

If the both methods carry some or some advantages and disadvantages (Such as in alphanumeric method, there are few disadvantages,such as; some characters may be eroded away with time, or could not seen from all directions, and there is also the scope of confusion in similar-shaped letter such as among numbers: 6,9; 2,5; 1,7 etc; and among letters (for-say if letters required in here or any-other alphanumeric code) such as b,d,p,q; C(Capital),c(small); and among Letters and numbers (O (capital-O for Owl),0(zero) ; l (Small-eL fore Logic) , I (Capital-aye) for iodine, and 1 (one) etc. ) ; the solution should be done by a new convention or meet, in few very simple way, like 1. Using both-the method on same time (so-that, from colored bands, the value could be seen from all-direction), as well alphanumeric method will be the main-basis to determine values; and 2. Using some distinction-mark (strike-outs, dots etc). to distinguish similar-looking characters (as they done sometimes) with well-publishing and popularizing the meaning of such notations.

Answer 5

I would say that mass production also plays a part in why there are still Color bands as well.

There is probably a lot of these still left from some company mass producing them a long time ago, and if they are still good and usable why throw them away or attempt to print numbers on them, there is no need to change something that people are already acquainted with, that still serves the purpose.

Otherwise, I would say it is because they are round and have no top or bottom like @tcrosley said.

Answer 6

Why change as we had a good system for over 50 years and most of us had a rhyme to remember the order of the colour codes. With the old system all I had to do was right down the coloured bands look up the colour codes and within a couple of minutes you had the value of the resistors.. Unlike today with the smd's you have to scroll through multiple columns of code to find what you are after. You have even got an app on your phone for the colour codes..