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'[EE] Why are individual resistors so damn big?!'
2008\06\24@205037 by Tomás Ó hÉilidhe

picon face

Have you seen those tiny little picofarad capacitors? Why aren't
resistors that small?

I've seen them fit 12 resistors into slimline SIP packages, so why do
they make individual resistors so big?

Is there any manufacturer that does smaller through-hole resistors? Even
better if they actually write the resistor value on it instead of
playing a colour game.

2008\06\24@211702 by Peter Todd

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On Wed, Jun 25, 2008 at 01:50:04AM +0100, Tomás Ó hÉilidhe wrote:
{Quote hidden}

Most resistors hobbiest use are rated to dissipate 1/4W of heat, however
you can buy through hole resistors rated for less than that, and those
resistors are comparitively smaller.

Search on digikey, you'll find them.

- --
http://petertodd.org 'peter'[:-1]@petertodd.org
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2008\06\24@212216 by Brent Brown

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On 25 Jun 2008 at 1:50, Tomás Ó hÉilidhe wrote:
> Have you seen those tiny little picofarad capacitors? Why aren't
> resistors that small?
>
> I've seen them fit 12 resistors into slimline SIP packages, so why do
> they make individual resistors so big?
>
> Is there any manufacturer that does smaller through-hole resistors? Even
> better if they actually write the resistor value on it instead of
> playing a colour game.

Primarily, resistor size is related to required heat disspation. Current through a
resistor produces heat according to P = V x I, or I x I x R. You really should know
this.

You can get really small resistors but they will have a relatively low power rating,
likewise you can get incredibly large resistors with very large power ratings.
Depends entriely on what you need. Which ones are you talking about? For
"general purpose" through hole resistors I like the Philips SFR16 series (or
whatever they are called now). They are rated at something like 0.4W ~ 0.5W, and
are easily mounted with 0.3" or even 0.2" lead spacing, still have colour coding
bands and are easy to read. The power rating of these little beasties is way better
than "normal/standard" 0.25W resistors BUT you don't get something for nothing
(you can not change the laws of physics...) so they will run very hot at their intended
maximum power (check data sheets).

--
Brent Brown, Electronic Design Solutions
16 English Street, St Andrews,
Hamilton 3200, New Zealand
Ph: +64 7 849 0069
Fax: +64 7 849 0071
Cell: +64 27 433 4069
eMail:  spam_OUTbrent.brownTakeThisOuTspamclear.net.nz


2008\06\24@212737 by Timothy J. Weber

face picon face
Tomás Ó hÉilidhe wrote:
> Have you seen those tiny little picofarad capacitors? Why aren't
> resistors that small?

The common ones you're probably using now are 1/4 W.  Search for 1/8 W
resistors; they're usually smaller.  (But of course, check your power
dissipation - P = I^2 * R.

Or use SMT.  I think the 1206 size will fit nicely across two adjacent
pads on a 0.1" perfboard.

And if tight horizontal spacing is what you're after, and vertical space
is available, you can always put them in on end at 0.1" spacing.
--
Timothy J. Weber
http://timothyweber.org

2008\06\24@213819 by Adam Field

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face
It's not a  "color game". There are many reasons why the color code
exists. The primary being that when it was introduced, it was easier
to band resistors than to try and print numbers on them. The second
that comes to mind is that the resistor can be placed at any angle and
still have its value readable.

Once you learn it, it becomes very easy to distinguish values from
each other. Especially when you have a pile of them on your workbench.

On Tue, Jun 24, 2008 at 8:50 PM, Tomás Ó hÉilidhe <.....toeKILLspamspam@spam@lavabit.com> wrote:
{Quote hidden}

>

2008\06\24@214818 by Jinx

face picon face
> Is there any manufacturer that does smaller through-hole resistors?

Sure. You can get 1/16W in through-hole. Did you look ?

parts.digikey.com/1/parts/1112192-resistor-10k-ohm-1-16w-5-axial-hr01
103jr.html

> Even better if they actually write the resistor value on it instead of
> playing a colour game.

What's so hard about the colour "game" ? If you switch to SMT
they have the value printed on them. You still have to figure out
that 684 means 68 and four zeroes though. If you're considering
this for manufacture, why would you worry about it anyway. You
just specify the part

2008\06\24@215355 by Tomás Ó hÉilidhe

picon face


Adam Field wrote:
> It's not a  "color game". There are many reasons why the color code
> exists. The primary being that when it was introduced, it was easier
> to band resistors than to try and print numbers on them. The second
> that comes to mind is that the resistor can be placed at any angle and
> still have its value readable.
>  

Really? I thought it was brought in to ostracise colour-blind people.

You say they can be read from any angle, but I bet you I can read "220
ohms" backwards and upside down handier than I can read a colour-band.

> Once you learn it, it becomes very easy to distinguish values from
> each other. Especially when you have a pile of them on your workbench.

Ah yes I've known the colours off by heart for a few years now, I
instinctively look for a "red red brown" when I'm playing around with
LED's. Despite that, I still think they're absolutely stupid in this day
and age, especially since they unfairly discriminate against
colour-blind people.

I can't think of anything more intuitive than having "220 ohms" printed
on a resistor.

I had a capacitor one time that had "10e9" printed on it; I went to the
wall chart to see what it was, and to my delight it was 10 nanofarrads.
I was actually surprised that the manufacturer actually showed some cop on.

2008\06\24@215813 by Brian B. Riley

picon face
Its more than that even, its called heat dissipation ...  the size  
allows the resistor to have sufficient surface area to do its job.  
That said, a lot of designers are still mentally stuck in the 1/4 watt  
sizing which in todays microcircuits is overkill ... 1/8 watt through  
hole resistors will do the job, and not occupy much space.

cheers ... BBR

On Jun 24, 2008, at 9:38 PM, Adam Field wrote:

{Quote hidden}

>> -

2008\06\24@220614 by Tomás Ó hÉilidhe

picon face


Jinx wrote:
>> Is there any manufacturer that does smaller through-hole resistors?
>>    
>
> Sure. You can get 1/16W in through-hole. Did you look ?
>
> parts.digikey.com/1/parts/1112192-resistor-10k-ohm-1-16w-5-axial-hr01
> 103jr.html
>  

Thanks for that.

Those component selector website yoke-a-ma-jiggies aren't my friend,
takes me yonks to find something, especially when they use words like
"axial".

> What's so hard about the colour "game" ? If you switch to SMT
> they have the value printed on them. You still have to figure out
> that 684 means 68 and four zeroes though.

Christ I really don't know why they couldn't write "680e3" or "680k".

2008\06\24@221313 by Jinx

face picon face
> Really? I thought it was brought in to ostracise colour-blind people

Based on what evidence ? That is just a ridiculous thing to say

> Ah yes I've known the colours off by heart for a few years now, I
> instinctively look for a "red red brown" when I'm playing around
> with LED's

So what's the beef if you know the colour code ?

> You say they can be read from any angle, but I bet you I can
> read "220 ohms" backwards and upside down handier than I
> can read a colour-band

They print values on diodes too, but you try reading those when
they're installed. And just how small will the writing be on a 1/8W
or 1/16W resistor ? Small enough to complain about that too ? It
makes sense for the commonest component to be the easiest to
read by the majority of people

2008\06\24@223256 by Robert Young

picon face


{Quote hidden}

And "axial" means along an axis.  Think "axel of a car" and you can visualize what the part looks like (well, more like the rear differential).  Not difficult, English language not withstanding.

And the text labeling is done that way to save space on the package and standardize across sizes/brands.  Ever try to write (screen print, laser etch) on an 0402 package...

Rob


2008\06\24@223625 by Tomás Ó hÉilidhe

picon face

Jinx wrote:
>> Really? I thought it was brought in to ostracise colour-blind people
>>    
>
> Based on what evidence ? That is just a ridiculous thing to say
>  

Obviously they weren't brought in specifically to ostracise colour-blind
people -- my comment was a snipe at how colour-blind people have been
ostracised for no good reason.

When I went to highschool (we call it secondary school in my country),
there were no wheelchair-bound people in my school, and there was
minimal wheelchair access. About a year or two after I left however, I
heard they'd gotten ramps and lifts installed (no doubt costing tens, if
not hundreds, of thousands of Euro). Funny thing about it though, is
that they got all that stuff in because *one sole student* was
wheelchair-bound.

Now of course I'm not against accommodating disabled people, I mean I
too would want ramps and stuff if I was wheelchair-bound, but I just
find it funny that on the one hand people will go to great lengths such
as spending hundreds of thousands of Euro to accommodate one
wheelchair-bound student, while on the other hand they'll say "sorry bud
you can't be an electrician coz you're colour-blind".

The colour code system for resistors is out-dated. It has no merit
whatsoever today in 2008. It's a relic of human insensitivity.

>> Ah yes I've known the colours off by heart for a few years now, I
>> instinctively look for a "red red brown" when I'm playing around
>> with LED's
>>    
>
> So what's the beef if you know the colour code ?
>  

Because I've been learning numbers since I was about 4 years old, and
I'll never be as proficient with the colour-code system as I am with
numbers.

Having to memorise or look-up the colour code system is an
inconvenience. (Not to mention the difficulty it poses for the
colour-blind).

> They print values on diodes too, but you try reading those when
> they're installed. And just how small will the writing be on a 1/8W
> or 1/16W resistor ? Small enough to complain about that too ? It
> makes sense for the commonest component to be the easiest to
> read by the majority of people
>  

Exactly you're right, we should print numbers on components.

2008\06\24@223950 by PicDude

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{Quote hidden}

No kidding -- after coming off the tape/reel, my thru-hole resistors go into
a bin, and when I need to look for one later, it's sooo easy to find it by
looking for the specific color pattern.

But I use more SMT parts nowadays and when I have individual unused 0805
resistors of mixed values laying around, I chuck them in the bin, because
I'd go crazy trying to flip each one over and read the values to look for a
specific one.

Cheers,
-Neil.


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2008\06\24@225028 by Jinx

face picon face
> especially when they use words like "axial"

Axial is a basic component description

http://en.wikipedia.org/wiki/Resistor

Resistor tutorial

http://ikalogic.com/beg_1_res_v_c.php

You should get some old circuit boards, perhaps a PC mobo,
PSU, VCR, TV etc and study and get the components off for
a spares box. I think that you'll find SMT predominates now
unless the component needs a particular rating. A general purpose
1206 or 0804 resistor costs a fraction of a cent. The last lot of
10k I bought for home use worked out at 0.09c. Equivalent value
in 1/4W by the 1000 is 2.1c. 5.6c if bought retail in 10s. Plus if
you're doing a double-sided PCB that does rule out compact
stuffing without using SMT

> I really don't know why they couldn't write "680e3" or "680k"

Then someone will come along and say "why can't they write
'680,000 ohms 1/4 watt 100VDC This Way Up' on it ?". And
then the answer to your question will be "They are so big so as
to fit all that writing on"

Maybe one of these manufacturers. Vishay is a market leader

http://www.interfacebus.com/resistors.html



2008\06\24@230034 by Jinx

face picon face
> The colour code system for resistors is out-dated. It has no
> merit whatsoever today in 2008. It's a relic of human insensitivity

I think you would probably encounter some resistance to that.
And quite a bit of eye-rolling to I shouldn't wonder

> Having to memorise or look-up the colour code system is an
> inconvenience. (Not to mention the difficulty it poses for the
> colour-blind).

What about the numerically challenged ? Or dyslexics ? Do you
think they might prefer colour bands ?

> Exactly you're right, we should print numbers on components

I've got some miniature zener diodes here with writing on them.
Glass bodies, transparent, with the diode gubbins inside. With
a head magnifier and a magnifying glass I still find it difficult to
make out exactly what the writing is. And if a bit of that writing
is scratched off, game over for a positive ID. If they had colour
bands though .....

2008\06\24@231825 by Jinx

face picon face
> Obviously they weren't brought in specifically to ostracise colour-
> blind people

I thought you said it was. Anyway, anyone can buy a meter. And
I don't see any reason why someone who is colour-blind can't do
electronics

And my recollection is that mains wiring colours were changed to
reduce colour-related mistakes. The adoption of a striped Earth
for example

http://www.iee.org/Publish/WireRegs/IEE_Harmonized_colours.pdf



2008\06\25@000528 by gardenyu

picon face
part 1 2385 bytes content-type:text/plain; charset="gb2312" (decoded quoted-printable)

 I think people really need to be told of the value just by looking at the resistors themselves.
However, it costs much to write numbers onto them compared to the total cost which is as cheap as dirt. Thus they just invented this foolish color code way. They say "it costs less for you, and you can still tell the value".
one day I looked at a chip with some number on it, I though it was some serial number, it turns out........production date...........



> From: .....rwybeakerKILLspamspam.....hotmail.com> To: EraseMEpiclistspam_OUTspamTakeThisOuTmit.edu> Subject: RE: [EE] Why are individual resistors so damn big?!> Date: Tue, 24 Jun 2008 21:32:17 -0500> > > > > > > Jinx wrote:> > >> Is there any manufacturer that does smaller through-hole resistors?> > >> > > >> > > Sure. You can get 1/16W in through-hole. Did you look ?> > >> > > http://parts.digikey.com/1/parts/1112192-resistor-10k-ohm-1-16w-5-axial-hr01> > > 103jr.html> > > > > > > Thanks for that.> > > > Those component selector website yoke-a-ma-jiggies aren't my friend, > > takes me yonks to find something, especially when they use words like > > "axial".> > > > > What's so hard about the colour "game" ? If you switch to SMT> > > they have the value printed on them. You still have to figure out> > > that 684 means 68 and four zeroes though.> > > > Christ I really don't know why they couldn't write "680e3" or "680k".> > > > And "axial" means along an axis. Think "axel of a car" and you can visualize what the part looks  like (well, more like the rear differential). Not difficult, English language not withstanding.> > And the text labeling is done that way to save space on the package and standardize across sizes/brands. Ever try to write (screen print, laser etch) on an 0402 package...> > Rob> > > -- > http://www.piclist.com PIC/SX FAQ & list archive> View/change your membership options at> mailman.mit.edu/mailman/listinfo/piclist
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2008\06\25@055212 by Dennis Crawley

picon face
On Wednesday, June 25, 2008 12:17 AM [GMT-3=CET],
Jinx  wrote:

>> Obviously they weren't brought in specifically to ostracise colour-
>> blind people
>
> I thought you said it was. Anyway, anyone can buy a meter. And
> I don't see any reason why someone who is colour-blind can't do
> electronics
>
> And my recollection is that mains wiring colours were changed to
> reduce colour-related mistakes. The adoption of a striped Earth
> for example
>
> http://www.iee.org/Publish/WireRegs/IEE_Harmonized_colours.pdf

Why they don't come on braille?
(I Remmember: In the 80's a group of radio hams did a multimeter in morse
for a blind old man)
I prefer colors. For developing, big white letters and numbers on the
chips,... not that laser etching. I usualy put some liquid paper over it,
and the written thingy comes up.

ok, what's next?
imperial measures? resistors scales?,... I think we already talk about
that... just in case:)
Dennis




2008\06\25@064710 by Jinx

face picon face
> ok, what's next?
> imperial measures? resistors scales?,... I think we already talk
> about that... just in case:)

I saw an episode of Smash Lab on Discovery the other night. The
Smash Lab team, American <cough>, were measuring up some steel
frame and "lumber"

Which is how my Granpa would walk home after Sunday lunch at
the pub, but they were actually talking about "timber". Which is what
he would do into The Big Comfy Chair In Front Of The TV

So, anyhoo, they've got this tape measure and are writing down
2 and 7/16 inches, 3ft 4 and a 1/4, 5ft 11 and 9/32, etc. And if you
looked closely you could see their eyes glaze as they attempted
some mental arithmetic

Then they met up with a fella who had some lead weights for sale.
"That 'un right  there is 50 kilos" - "Oh, right, so that's like 100
pounds ?". And so on and so on

Most irritating to be truthful

(I don't mean "it's irritating to be truthful", honesty is always the best
policy)

I'm all for nostalgia and did learn UK imperial - I wish you could still
buy petrol by the hogshead and condoms by the firkin box - (oh, haha,
I just got my own joke) but when your system is making life slower
and more difficult, is it too much to change ? Even on a project like
they were doing when the actual units didn't matter, it was the physical
relationships of dimensions eg this needs to be a third as long as that

Would you rather mentally divide 5ft 11 and 9/32 inches by 3 or
1810mm by 3 ?

2008\06\25@081336 by Rolf

face picon face
Jinx wrote:
>> ok, what's next?
>> imperial measures? resistors scales?,... I think we already talk
>> about that... just in case:)
>>    
>
> I saw an episode of Smash Lab on Discovery the other night. The
> Smash Lab team, American <cough>, were measuring up some steel
> frame and "lumber"
>
>  
[snip imperial/metric stuff]
> Would you rather mentally divide 5ft 11 and 9/32 inches by 3 or
> 1810mm by 3 ?
>
>  

Hi Jinx.

I'm living in Canada now (for 8 years), but born and raised in South
Africa and then spent many years in UK too. I was raised 'metric'. But,
now that I have a basement, mitre-saw, table saw, and a wood-framed
house, I have discovered that imperial is fantastic when it comes to
measuring things. At least in terms of wood. As it happens, 12 is a
fantastic 'base' to do maths in. Much better than decimal (10). 12 is
divisible by 2,3,4,6 wheras 10 is divisible by only 2 and 5. Further,
with my computer science education, I am very happy with working in the
'imperial' fractions, where the denominators are powers of 2 (1/2 1/4
1/8 1/16 1/32 etc).

Bottom line, for common 'construction' challenges, the system works very
well. Common operations alike dividing a space in to thirds is much
easier than in metric....

For what it's worth, the problem with the examples you cited with
5'11"9/32 is that there are one too many units involved. For the actual
division you really want to convert the 5' to ", and you then have
71"9/32 which is easy to solve in your head as 69" / 3 + 2"/3 + (9/32)/3
which is 23" + 2/3" + 3/32", which, you have to know that 1/3 inch is
approximately 5/16, or more closely 11/32, so, the answer is 23"25/32  
(which has an error of 0.02")

Now, in your head, what is a third of 4m 22cm 5mm ?

You see, multiple units is never a good thing for mental math... but,
even converted to a single unit 4225 / 3 ?

Rolf

2008\06\25@082216 by olin piclist

face picon face
Tomás Ó hÉilidhe wrote:
> Have you seen those tiny little picofarad capacitors? Why aren't
> resistors that small?

I don't know what you mean by "little picofarad capacitors", but resistors
are available in small packages like 0402 just like capacitors.  Unless you
are using machine placement, you really don't want to be using 0402.

I find 0805 a comfortable size to do by hand, and 0603 doable with a
magnifier if I have to.  Resistors are widely and cheaply available in both
these sizes, although I only keep 0805 routinely in stock.

In some cases you need physically bigger resistors due to power dissipation.
For capacitors, the limit becomes maximum voltage.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2008\06\25@083044 by Alan B. Pearce

face picon face
>I had a capacitor one time that had "10e9" printed on it; I went to the
>wall chart to see what it was, and to my delight it was 10 nanofarrads.
>I was actually surprised that the manufacturer actually showed some cop on.

Hmm, wonder how you will get on with SMD capacitors that don't have
markings - not even colour bands ...

2008\06\25@083127 by olin piclist

face picon face
Tomás Ó hÉilidhe wrote:
> but I bet you I can read "220
> ohms" backwards and upside down handier than I
> can read a colour-band.

Perhaps, until you get better at reading color bands.

> Despite that, I still think they're absolutely stupid

You should stop and learn something about a field before deciding what's
stupid and what isn't.  You really need a better attitude if you're going to
succeed at electronics (or anything else).

> especially since they unfairly discriminate against
> colour-blind people.

You mean like using red/green bicolor LEDs to convey information?


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2008\06\25@085049 by Derward Myrick

picon face

Jinx, it looks as if someone is troling with nthis sybject.

Derward


----- Original Message -----
From: "Jinx" <joecolquittspamspam_OUTclear.net.nz>
To: "Microcontroller discussion list - Public." <@spam@piclistKILLspamspammit.edu>
Sent: Tuesday, June 24, 2008 9:11 PM
Subject: Re: [EE] Why are individual resistors so damn big?!


{Quote hidden}

> --

2008\06\25@085135 by Spehro Pefhany

picon face
Quoting "Alan B. Pearce" <KILLspamA.B.PearceKILLspamspamrl.ac.uk>:

>> I had a capacitor one time that had "10e9" printed on it; I went to the
>> wall chart to see what it was, and to my delight it was 10 nanofarrads.
>> I was actually surprised that the manufacturer actually showed some cop on.
>
> Hmm, wonder how you will get on with SMD capacitors that don't have
> markings - not even colour bands ...

And SMT resistors below 0402..

When stuff is assembled and tested by machine, there's really very  
little need for markings at all. Mostly it will never be repaired, and  
for in-house testing and rework, they have big maps of what should be  
where (with coordinates).

Best regards,
Spehro Pefhany
--
"it's the network..."                          "The Journey is the reward"
RemoveMEs...TakeThisOuTspaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

2008\06\25@085439 by Jinx

face picon face
> 71"9/32 which is easy to solve in your head as 69" / 3 + 2"/3
> + (9/32)/3

I might have gone the other way seeing as it's so close to 6ft

72/3 - ((32-9)/3)

> Now, in your head, what is a third of 4m 22cm 5mm ?

> You see, multiple units is never a good thing for mental math... but,
> even converted to a single unit 4225 / 3 ?

4200/3 is an easy one, if you know your 1400 times table, then +25/3.
One of my pocket money jobs is cutting mdf sheet for a picture framer
and that's all done in mm, with a little mental planning sometimes to
work out the best cut from an 8 x ... ooops, a 2440 x 1220 sheet

Not prosyletising for either, each has its merits

The only imperial measure I've got left is dad's old fold-up carpenter's
rule. Everything else is metric. And I do look out for an imperial ruler
as I still make my own PCBs and it's helpful to transfer some drawing
measurements on gridded paper to the copper

Now that I think of it, I should print my own 0.1" scale and laminate it

And every time I use it I'll bang on Elgar's Pomp And Circumstance
March No1 at a volume sufficient to waken dead heroes and shed a
silent tear for days gone by

2008\06\25@085632 by Andrew Burchill

picon face
> The colour code system for resistors is out-dated. It has no> merit
whatsoever today in 2008. It's a relic of human insensitivity

my $0.02 on this from a service technicians point of view is that SMD is
leading
us at an accelerating rate further into the disposable society.
I really don't have anything against SMD parts, there are plenty of merits,
but introduce a case where a piece of equipment that is only a few years
old,
fails and stops working. upon inspection two or three SMD resistors and
maybe a Dpak device have volcanic holes in them. Unless you have original
circuit schematic (not always the case in the repair industry) then you're
out of luck, unless the circuit is easy to reverse engineer (factor in
economies of scale).
When thru-hole components were more common, if something let the smoke out
then generally there was enough left to ID the part by colour,  value or
number,
then find and fit new parts.
An observation of most consumer equipment currently puts the average
lifespan
of said equipment at less than 5 years. and at this rate in another 5 years,
expected equipment lifespan will be under 3 years.
I'm currently maintaining equipment that was produced in 1994, manufacturer
support stopped in 1998, but the owner(s) expect to continue usage
indefinitely
(realistically probably at least another 5 years).

Andrew

2008\06\25@085825 by Jinx

face picon face
> especially since they unfairly discriminate against colour-blind
> people

> You mean like using red/green bicolor LEDs to convey information?

Ouch, Zing !


2008\06\25@091911 by Tomás Ó hÉilidhe

picon face


Jinx wrote:
>> You mean like using red/green bicolor LEDs to convey information?
>>    
>
> Ouch, Zing !

Find me someone who can't tell the difference between red and green.

Red and brown, now, that's another story. When I was a kid I used to
play snooker with this other kid that was colour blind; I used to love
it when he potted the brown ball thinking it was a red.

2008\06\25@092118 by Jinx

face picon face
> Hmm, wonder how you will get on with SMD capacitors that
> don't have markings - not even colour bands ...

That's odd that caps are left blank. They can be the same size as
marked resistors, and are generally brown, resistors are black, so
it's unlikely you'd confuse two components with the same number

I scavenge SMT ceramics to sprinkle around boards for decoupling
and don't think I've seen a non-polarised cap yet with a value printed
on it

A quick Google doesn't provide an answer why, but all the mftrs
seem to do it

2008\06\25@092312 by Gerhard Fiedler

picon face
Rolf wrote:

> Now, in your head, what is a third of 4m 22cm 5mm ?

If you're asking this, you haven't understood the relationship between the
"metric" system (which is only called so by the "imperials" :) and our
number system. No one working with SI units would even think of giving a
length in that form. It's either 4.225m, 422.5cm or 4225mm (to cite the
more common ways), and it's easy to convert between the three.

> You see, multiple units is never a good thing for mental math...

Exactly. That's one beef with imperial units; the conversions between them
don't match the number system you're doing it in, which complicates
matters. I agree with you that a base-12 number system has advantages, but
I challenge you to do the math in your head, using a /real/ base-12 system
:)  I think I stick with the decimal system, at least as long as everybody
else does it.

> even converted to a single unit 4225 / 3 ?

You're talking about building, so generally you wouldn't measure in mm, but
in m. (Maybe in cm, if you're thinking from a woodworking perspective, but
the changes to the following are minimal -- due to the use of a number
system that matches the unit system.) That would then be 4.225m. 4.2m / 3
is easy; that's 1.4 m. If you need the precision and want to add the
remaining 25 mm / 3, you can do that just as easily: 1.4 m + 8 mm = 1.408
m. I think that's a lot less meddling around with numbers than what you
described: two simple divisions and an even simpler addition, without
"having to know" much :)

Gerhard

2008\06\25@092830 by Robert Young

picon face

>
> > Hmm, wonder how you will get on with SMD capacitors that
> > don't have markings - not even colour bands ...
>
> That's odd that caps are left blank. They can be the same size as
> marked resistors, and are generally brown, resistors are black, so
> it's unlikely you'd confuse two components with the same number
>
> I scavenge SMT ceramics to sprinkle around boards for decoupling
> and don't think I've seen a non-polarised cap yet with a value printed
> on it
>
> A quick Google doesn't provide an answer why, but all the mftrs
> seem to do it

Affects the value perhaps?

Rob

2008\06\25@093121 by Alan B. Pearce

face picon face
>> Hmm, wonder how you will get on with SMD capacitors that don't have
>> markings - not even colour bands ...
>
>And SMT resistors below 0402..

Or many MIL-Spec SMD resistors of any size, certainly the 1206 space
qualified ones we get are unmarked.

2008\06\25@093149 by Gerhard Fiedler

picon face
Jinx wrote:

> Then someone will come along and say "why can't they write
> '680,000 ohms 1/4 watt 100VDC This Way Up' on it ?".

And completely forgetting that "680,000 ohms" is way too ambiguous to be
used in production. Where was this resistor manufactured? Was that in a
country that uses a decimal comma (meaning 680 ohms to a precision of three
digits after the comma) or  in one that uses a decimal point and a comma to
separate thousands (meaning 680 kiloohms; yes, if you want to stay in this
game, you should become familiar with SI prefixes, even though they all
could be replaced by potencies of ten)?

BTW, you forgot to print the precision... :)

And BTW, to lessen the confusions with decimal point, decimal comma and
thousand separators, ISO (IIRC) suggests to use the apostrophe as thousand
separator. Both points and commas then become interchangeable decimal
separators. "680'000" seems to be less ambiguous than both "680,000" and
"680.000". (Of course, that still doesn't help much when you only see
either of the two :)

Gerhard

2008\06\25@093725 by olin piclist

face picon face
Tomás Ó hÉilidhe wrote:
> Find me someone who can't tell the difference between red and green.

That's actually the single most common form of color blindness.  Look it up.


********************************************************************
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(978) 742-9014.  Gold level PIC consultants since 2000.

2008\06\25@094629 by Jinx

face picon face
> Find me someone who can't tell the difference between red and
> green

They seem to be more common than I thought

http://en.wikipedia.org/wiki/Color_blindness

Deuteranopia is a color vision deficiency in which the green retinal
photoreceptors are absent, moderately affecting red-green hue
discrimination. It is a form of dichromatism in which there are only
two cone pigments present. It is likewise hereditary, sex-linked, and
present in 1% of all males

Protanomaly is a mild color vision defect in which an altered spectral
sensitivity of red retinal receptors (closer to green receptor response)
results in poor red-green hue discrimination. It is hereditary, sex-linked,
and present in 1% of all males. It is often passed from mother to child

Deuteranomaly, caused by a similar shift in the green retinal receptors,
is by far the most common type of color vision deficiency, mildly affecting
red-green hue discrimination in 5% of all males. It is hereditary and sex-
linked


2008\06\25@094924 by Nicola Perotto

picon face
This link is only for the Dickhead list...

http://en.wikipedia.org/wiki/Colour_blind#Red-green_color_blindness



Tomás Ó hÉilidhe wrote:
{Quote hidden}

2008\06\25@095947 by Rolf

face picon face
Gerhard Fiedler wrote:
{Quote hidden}

Of course, if you used the SI unit, and it was printed 6800'000 on a
1206, then Thomàs would worry that it was really a 0.0089 resistor
because he read it upside-down..... actually, that could be a problem
with the current scheme too ... how about 911, a 910Ohm resistor, or is
that a 11M resistor....

Rolf

2008\06\25@105625 by M. Adam Davis

face picon face
It's good to have newcomers in a field which has so many "that's just
how it's always been" methods and means.

New blood helps us look at ourselves critically.

In the case of resistors, there are several considerations:
* Machine vision systems can significantly more easily ID color coded
resistors than numbers
* It's much easier to print - if you want numbers on a round resistor
you have to print them several times around the cylinder or else they
can't be seen as readily.
* Color bands are much larger and therefore easier to read - imagine
printing numbers on the resistor itself - they're going to be tiny,
and being on a curved surface they won't be as simple to read and see
as color bands.
* "This is the way it's always been done" is a valid ongoing reason -
it works, and changing over would introduce a huge cost to
manufacturing (which would pass down to us), not to mention how
they're used (machine vision checking, etc)
* We're moving more towards another package (SMT) entirely anyway, so
why revamp a system that it slowly going away?

Regarding printing resistor values with less cryptic numbers:
* There's simply not enough room to make it legible.
* You need more digits to specify your system (6834 vs 9.76M, and
unless you give the decimal a full digit's worth of space it's hard to
identify)
* Your example of 10e9 is great - but if you're always going to have
the e, then why not simply remove it and mark the capacitor 109?
* Further, what is the base unit, and how do you specify values
smaller than the base unit without adding more characters?

In this case, I believe you'll just have to live with the decisions
others made in this industry years ago.  As you can see, most of the
engineers on this list largely agree with how the system works now,
but please do bring up other issues as you learn.

It's always good to revisit past decisions, even if they arent' going
to change - they may positively affect current decisions.

-Adam

On 6/24/08, Tomás Ó hÉilidhe <spamBeGonetoespamBeGonespamlavabit.com> wrote:
{Quote hidden}

>

2008\06\25@112328 by Alan B. Pearce

face picon face
>And BTW, to lessen the confusions with decimal point, decimal comma and
>thousand separators, ISO (IIRC) suggests to use the apostrophe as thousand
>separator. Both points and commas then become interchangeable decimal
>separators. "680'000" seems to be less ambiguous than both "680,000" and
>"680.000". (Of course, that still doesn't help much when you only see
>either of the two :)

But the OP also forgot about why you don't need all those zeros, they do not
add anything to the value, so why not just put 680k ...

and for decimal points do it the way many Europeans draw their schematics,
and use the multiplier letter as the decimal point, so you get 6k8 ...

2008\06\25@112636 by Michael Rigby-Jones

picon face


> -----Original Message-----
> From: TakeThisOuTpiclist-bouncesEraseMEspamspam_OUTmit.edu [RemoveMEpiclist-bouncesspamTakeThisOuTmit.edu] On
Behalf
> Of Jinx
> Sent: 25 June 2008 02:47
> To: Microcontroller discussion list - Public.
> Subject: Re: [EE] Why are individual resistors so damn big?!
>
> What's so hard about the colour "game" ? If you switch to SMT
> they have the value printed on them

Only the "big" ones!  Chasing 0603's around a bench with meter probes is
fun, but 0402's are a nightmare.

I lament the passing of colour codes, all those days reciting rude poems
in my head have gone to waste :D

Cheers

Mike

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2008\06\25@123136 by Tomás Ó hÉilidhe

picon face


Olin Lathrop wrote:
> Tomás Ó hÉilidhe wrote:
>  
>> Find me someone who can't tell the difference between red and green.
>>    
>
> That's actually the single most common form of color blindness.  Look it up.
>  

Thanks for that, I learn something new every day. I'm gonna try find
different colour LED's.

2008\06\25@124859 by Tomás Ó hÉilidhe

picon face


Tomás Ó hÉilidhe wrote:
> Thanks for that, I learn something new every day. I'm gonna try find
> different colour LED's.

I'm after sending an e-mail to a colour-blind association asking them
what are the two best colours to use. I'll let you know what response I get.

2008\06\25@131047 by Tomás Ó hÉilidhe

picon face


Tomás Ó hÉilidhe wrote:
> I'm after sending an e-mail to a colour-blind association asking them
> what are the two best colours to use. I'll let you know what response I get.

So far it looks like the best combination is Magneta and Green. The
following page gives some nice info:

http://jfly.iam.u-tokyo.ac.jp/color/

2008\06\25@143354 by Herbert Graf

flavicon
face

On Wed, 2008-06-25 at 14:18 +0100, Tomás Ó hÉilidhe wrote:
>
> Jinx wrote:
> >> You mean like using red/green bicolor LEDs to convey information?
> >>    
> >
> > Ouch, Zing !
>
> Find me someone who can't tell the difference between red and green.

I SERIOUSLY hope you are kidding. Red-Green colour blindness is the MOST
COMMON form...

No matter WHAT you label your resistors with, you will be discriminating
against someone. You like numbers right? What about farsighted people?
What about illiterate people?

2008\06\25@164438 by Carl Denk

flavicon
face

This isn't that funny, but coincidence, today I was at a "Problem
Solving" seminar to satisfy my states continuing education requirements
for registered engineers. There was a practical exercise where the class
broke into two teams and assemble a number of bolts with different
colored hex nuts. One team was given written instructions, the other
photos of the completed items. The random selected manager with the
photos was color blind. :)

Herbert Graf wrote:
{Quote hidden}

>

2008\06\25@164926 by Gerhard Fiedler

picon face
Alan B. Pearce wrote:

>> And BTW, to lessen the confusions with decimal point, decimal comma and
>> thousand separators, ISO (IIRC) suggests to use the apostrophe as
>> thousand separator. Both points and commas then become interchangeable
>> decimal separators. "680'000" seems to be less ambiguous than both
>> "680,000" and "680.000". (Of course, that still doesn't help much when
>> you only see either of the two :)
>
> But the OP also forgot about why you don't need all those zeros, they do
> not add anything to the value, so why not just put 680k ...

Of course. That was meant as a more general comment, more useful for
numbers in a text than on a component :)

> and for decimal points do it the way many Europeans draw their
> schematics, and use the multiplier letter as the decimal point, so you
> get 6k8 ...

Ah yes... being European by origin, I grew up with that and it's quite
natural to me. But I have learned not to rely on it being universally
understood -- not even in Europe by people with a technical but not
electronics background. This notation seems to be limited to electronics,
and to cases where the actual unit can be omitted.

Gerhard

2008\06\25@174604 by olin piclist

face picon face
M. Adam Davis wrote:
> It's good to have newcomers in a field which has so many "that's just
> how it's always been" methods and means.
>
> New blood helps us look at ourselves critically.

Yes that's fine, but the newcomer shouldn't come barrelling in declaring the
current system stupid before understanding why it is the way it is.
Sometimes the old way is no longer reasonable because the world changed
around it, but most of the time, especially in a competetive industry there
is good reason things are the way they are.  If you think something is
stupid, your first assumption should be that it only appears stupid because
you don't understand all the tradeoffs.  The right approach is to ask why it
is the way it is, not arrogantly complaining it is stupid before getting all
the facts.

Whether thru hole resistors should be labled with color rings or some other
method doesn't matter anyway.  Since thru hole resistors are obsolete, I
doubt there are new machines being designed to make them.  This means these
resistors will be made on the existing machines which use the existing color
code method, whether that is the best method for today or not.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2008\06\25@174834 by olin piclist

face picon face
Alan B. Pearce wrote:
> and for decimal points do it the way many Europeans draw their
> schematics, and use the multiplier letter as the decimal point, so
> you get 6k8 ...

Because it's really annoying to read?

********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2008\06\25@175410 by olin piclist

face picon face
Tomás Ó hÉilidhe wrote:
> I'm after sending an e-mail to a colour-blind association asking them
> what are the two best colours to use. I'll let you know what response
> I get.

There are various forms of color blindness, so there is no one right answer.
For complete color blindness, which is actually quite rare, only the
brightness matters, not the color.  The best approach to easily distinguis
the states is to use separte LEDs.  That way the information is encoded in
position, the LEDs are easier to drive, and you have a much wider range to
choose from.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2008\06\25@183636 by Jinx

face picon face
> play snooker with this other kid that was colour blind; I used to
> love it when he potted the brown ball thinking it was a red.

You'd think they'd have the colours written on them eh ?

Of course you have to be careful where you whip out a Magic
Marker and ask "Can I write names on your balls ?". Pretty
much a quick way of saying "You four big guys please beat
the snot out of me with cues, take me for a ride in the trunk of
your car and bury me in some foundations down town. And
hurry up about it, jerks". Of which they'll oblige you with before
you an say "kiss the pink"


2008\06\25@183823 by Tomás Ó hÉilidhe

picon face


Olin Lathrop wrote:
> Tomás Ó hÉilidhe wrote:
>  
>> I'm after sending an e-mail to a colour-blind association asking them
>> what are the two best colours to use. I'll let you know what response
>> I get.
>>    
>
> There are various forms of color blindness, so there is no one right answer.
>  


Yes there are different forms, but it seems that there's a "common
denominator" when it comes to choosing two colours to have side by side:
Magenta and Green.


> For complete color blindness, which is actually quite rare, only the
> brightness matters, not the color.


As I've already demonstrated, I'm no expert on colour-blindness, but
from what I've read, "full colour blindness" is a progressive illness
that leads to actual blindness, and it is indeed extremely rare.

Red-green colour-blindness on the other hand is quite common:
   1 in 12 white people
   1 in 20 asian people
   1 in 25 black people


> The best approach to easily distinguis
> the states is to use separte LEDs.  That way the information is encoded in
> position, the LEDs are easier to drive, and you have a much wider range to
> choose from.

I'm not sure what you envision, but I don't see how it would look good
if I replaced each bi-colour LED with two separate LED's side by side.

2008\06\25@185809 by Jinx

face picon face
> It's good to have newcomers in a field which has so many "that's
> just how it's always been" methods and means

If nothing else, the [EE] and [PIC] traffic sure has gone way up in
volume, and most of it is legitimate. Scarcely an [OT] for ages. I
hesitate to draw a link between that and Russell being in China ;-)

BTW, Tomas, I hope you realise that we're all generally quite
light-hearted and don't intend to be too mean-spirited when
answering your questions. But you have tripped off a couple of
your own mines. Got to be careful giving people ammo. And
then handing over the gun too (hmmm, rather a military theme
there)

Your topics have actually raised some interesting issues

Named snooker balls for the colour-blind - are there products
that could be enhanced ? Not that you want the place looking
like a half-finished paint-by-numbers. Or the Bat Cave

And the LED colour selection for the Connect 4 game. Now
I think perhaps you get an inkling of how much work a circuit
design really needs before you can call it a "Product"

2008\06\25@190746 by Jinx

face picon face
> > and for decimal points do it the way many Europeans draw their
> > schematics, and use the multiplier letter as the decimal point, so
> > you get 6k8 ...
>
> Because it's really annoying to read?

You know in an ideal world every image and every reader would be
perfect, but the fact is a dot is easily lost or added. Personally I don't
like DPs in schematics and prefer multipliers, eg 0u1, 6k8, as a more
durable nomenclature

2008\06\25@193104 by Tomás Ó hÉilidhe

picon face

Jinx wrote:
> If nothing else, the [EE] and [PIC] traffic sure has gone way up in
> volume, and most of it is legitimate. Scarcely an [OT] for ages.


I love the whole OT thing! Fair enough this "forum" is supposed to be
about PIC's but it's great to be able to have discussions about all
sorts of stuff :-D


{Quote hidden}

I've no problem with people advising me to read datasheets, but it's all
about the demeanour and deliverance.


> Your topics have actually raised some interesting issues
>
> Named snooker balls for the colour-blind - are there products
> that could be enhanced ? Not that you want the place looking
> like a half-finished paint-by-numbers. Or the Bat Cave
>  


I'd go with patterns probably... coloured patterns! People who have
difficulty with patterns can work off the colours, and the colour-blind
can work off the patterns. If you're colour-blind and have difficulty
with patterns... well... I feel for you.

In professional snooker, (the kind where they dress ridiculously),
there's very few things you can ask of the referee. One of the things
you can ask though, is for him to identify which ball is which if you
have difficulty distinguishing.


> And the LED colour selection for the Connect 4 game. Now
> I think perhaps you get an inkling of how much work a circuit
> design really needs before you can call it a "Product"


By switching from Red-Green to Magenta-Green, I've just opened up my
product to a previous 8% of people that I had marginalised. What's 8% of
73 million Euro? :-D

2008\06\25@200813 by Jinx

face picon face
> By switching from Red-Green to Magenta-Green

Colour-blindness wasn't the reason for the suggestion to look at
discrete LEDs instead of a bi-colour package, but I did mention
that there's a much better range for individual LEDs

It always helps to have a Plan B. Being locked in to a component
that you can do nothing to change, and having a PCB made to use
that component, may come back to haunt you. And cost $$$ to fix

A little quiet time and some imagery and day-dreaming can inspire
major beneficial changes to a design


2008\06\26@001314 by William \Chops\ Westfield

face picon face

On Jun 25, 2008, at 10:09 AM, Tomás Ó hÉilidhe wrote:

> So far it looks like the best combination is Magneta and Green.
>    http://jfly.iam.u-tokyo.ac.jp/color/

The way I read the page, they're recommending that red be replaced  
with magenta to retain some hint of "true color" while improving  
things for the color blind.  But if you're able to pick ANY two  
colors without regard to retaining anything "natural", it looks to me  
like the best bet would be yellow and blue.  (Interestingly, I don't  
think that's a combination that I've ever seen in two-color LEDs.  I  
wonder why not?)

BillW

2008\06\26@003903 by Marcel Birthelmer

flavicon
face
You could go with an RGB LED... R+G = yellow, and blue.
- Marcel

On Wed, Jun 25, 2008 at 9:12 PM, William Chops Westfield <westfwEraseMEspam.....mac.com>
wrote:

{Quote hidden}

>

2008\06\26@045037 by Dennis Crawley

picon face
On Wednesday, June 25, 2008 8:30 PM [GMT-3=CET],
Tomás Ó hÉilidhe  wrote:

> By switching from Red-Green to Magenta-Green, I've just opened up my
> product to a previous 8% of people that I had marginalised. What's 8% of
> 73 million Euro? :-D

How about using only one type of LED, no matter what color is, and you blink
it 10 times faster than the "game over" blink.
I'm thinking about 10Hz or something.

Oh, I see!, with this solution you just lost 5% of your target which suffer
epilepsy :)

Dennis.


2008\06\26@065545 by Alan B. Pearce

face picon face
>> you get 6k8 ...
>
>Because it's really annoying to read?

Well, annoying until you miss the decimal point on a schematic and read 6.8k
as 68k, because it hasn't printed very well.

Once you get used to it, the translation in the mind is just the same as
colour band values to English (or whatever your natural language is).

2008\06\26@070006 by Alan B. Pearce

face picon face
>As I've already demonstrated, I'm no expert on colour-blindness, but
>from what I've read, "full colour blindness" is a progressive illness
>that leads to actual blindness, and it is indeed extremely rare.

Some people are born fully colour blind. I remember the son of a friend who
had full colour blindness, when colour TV was about to be introduced, asked
'why, its in full colour already' ...

2008\06\26@070444 by Alan B. Pearce

face picon face
>I've no problem with people advising me to read datasheets,
>but it's all about the demeanour and deliverance.

The same is also true for the way questions are asked, and unfortunately
some of the ones you have presented have been done in 'gunslinger manner'.

2008\06\26@071026 by olin piclist

face picon face
Tomás Ó hÉilidhe wrote:
> As I've already demonstrated, I'm no expert on colour-blindness, but
> from what I've read, "full colour blindness" is a progressive illness
> that leads to actual blindness, and it is indeed extremely rare.

That's only one form caused by a disease.  The genetic version (no cones or
no pigments in the cones) doesn't lead to blindness, but the person sees in
shades of gray only, like a black and white TV.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2008\06\26@081241 by Spehro Pefhany

picon face
At 07:04 AM 6/26/2008, you wrote:
> >I've no problem with people advising me to read datasheets,
> >but it's all about the demeanour and deliverance.
>
>The same is also true for the way questions are asked, and unfortunately
>some of the ones you have presented have been done in 'gunslinger manner'.

Based, in part, on the OP's recent USENET history, I'd say "troll mode"
would be more accurate.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
EraseMEspeffspaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com



2008\06\26@161256 by Richard Prosser

picon face
2008/6/26 Alan B. Pearce <RemoveMEA.B.PearceEraseMEspamEraseMErl.ac.uk>:
>>As I've already demonstrated, I'm no expert on colour-blindness, but
>>from what I've read, "full colour blindness" is a progressive illness
>>that leads to actual blindness, and it is indeed extremely rare.
>
> Some people are born fully colour blind. I remember the son of a friend who
> had full colour blindness, when colour TV was about to be introduced, asked
> 'why, its in full colour already' ...
>


A mate of mine at university had the same problem. The biggest
difficulty he had was traffic lights, at night.

RP

2008\06\28@014441 by Yair Mahalalel

flavicon
face
On Wed, Jun 25, 2008 at 10:56:20AM -0400, M. Adam Davis wrote:

> Regarding printing resistor values with less cryptic numbers:
>  * There's simply not enough room to make it legible.
>  * You need more digits to specify your system (6834 vs 9.76M, and
> unless you give the decimal a full digit's worth of space it's hard to
> identify)
>  * Your example of 10e9 is great - but if you're always going to have
> the e, then why not simply remove it and mark the capacitor 109?
>  * Further, what is the base unit, and how do you specify values
> smaller than the base unit without adding more characters?

There is also the problem of realizing in what format the markings are
presented; there are many cases where constraints demand that one
compress the data to a few characters, and it isn't trivial to
tell in what way it was done.

In my recent project I guess I was distracted when I assembled the basic
PIC circuitry, and was perfectly content to use a cap marked 221K for
decoupling the PIC internal USB power supply, probably thinking something
like 22*10^1 kilo-pico-Farad=0.22uF should be alright.

The PIC worked fine, but for two weeks my USB bus would go haywire at
random - attaching a scope probe, touching the table, soldering a
different board, almost anything would make the computer spew a ton of
EMI warnings and require reloading or reattaching all the devices.

Only after replacing all the mains cables in the room, and going over all
the parts on the board (by then a shroud of wire wrap mashes, solder
puddles and secondary boards) I worked my way to the center and found my
stupid mistake - in the context of capacitors a K postfix is a
designation of precision, not a value modifier, and my cap was a
thousand times smaller than I thought.

At least with color bands you know what they're supposed to mean. There
is also an old capacitor color band code, but these usually look
different.

As an aside, I think you'd be hard pressed to come with methods which
are completely non-discriminatory (except by using UV and IR LEDS,
perhaps). Specifically Roman numerals will discriminate against users of
Arabic/Jewish/other systems, and that's a way you really don't want to
go ;-).

Cheers,
Yair.

2008\06\28@091635 by Electron

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At 22.56 2008.06.25, Olin Lathrop wrote:
>Tomás Ó hÉilidhe wrote:
>> I'm after sending an e-mail to a colour-blind association asking them
>> what are the two best colours to use. I'll let you know what response
>> I get.
>
>There are various forms of color blindness, so there is no one right answer.
>For complete color blindness, which is actually quite rare, only the
>brightness matters, not the color.  The best approach to easily distinguis
>the states is to use separte LEDs.  That way the information is encoded in
>position, the LEDs are easier to drive, and you have a much wider range to
>choose from.

and don't forget to make things HUGE, since total color blindness means
no cones in the retina, and no cones means no fovea, and no fovea means
extremely bad visual acuity (1/20th to 1/10th).



>
>
>********************************************************************
>Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
>(978) 742-9014.  Gold level PIC consultants since 2000.
>

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