Resistors: My FAQ

[Dolmetscher007]

Here is the Schematic: http://permanentelectronics.com/DIY/P.E.CSSTB.rev1/P.E._Colorsound.Supa.rev1.pdf
Here is the BOM: http://permanentelectronics.com/DIY/P.E.CSSTB.rev1/P.E._Colorsound.Supa.rev1.BOM.pdf
Here is a picture of the blank PCB and loaded up with all parts: http://permanentelectronics.com/

You can see in the BOM that it calls for the following resistors:

4x -- 100k
4x -- 100R
5x -- 10k
1x -- 1M
1x -- 2k7
3x -- 33k
4x -- 470k

1x --   560R  - 1k

1x -- CLR   4.7 - 12k

The first two seem to me to be the same. 100k resistors and 100R resistors, according to the articles I've read, are the same thing. The 100R is how they write it in Europe, and the 100k is more US.  Same thing a little later on with the 2k7... is that not the same as 2.7kOhms?
Why would the guy that made up this BOM and PCB mix and match the US/Euro standards?

Also... the last two: the 560R  - 1k   | and |  the 4.7 - 12k... why the range? This same BOM/project had a range listed for the capacitors too. If you look, one of the caps says 25V or more.

Why would a designer not give a specific "best practice" value, and then, if absolutely necessary list other options? I don't know what part to order.

[mth5044]

100R and 100k are different. 100k is 100,000 ohms, where 100R is just 100. I think people use the R to say it's not K or M. Really it should just be 100 ohms, but the R replaces it.

2k7 = 2.7k. Sometimes it's hard to read the . On photocopies or whatnot, so the k is out in the middle to make it clear that 2.7k is 2k7, and not 27k

CLR has a range as you would pick it depending on what kind of LED you are using and desired brightness.

R7, not sure why the range.

Voltage rating is the minimum voltage the designer wants you to get. Get a 50V, 450V, doesn't matter (it really does because they are different sizes), but it's what you can source and what you can fit on the PCB.

Edit: the "B or A" note on the pots is confusing. The controls will operate differently depending on which is chosen. That seems like an odd choice to let up to the builder.

[bluebunny]

the US/Euro standards

It's not about standards: it's about clarity and readability (for the reasons Matt mentioned).  And it's nothing to do with proximity to the Atlantic.      And we use "R" because we don't have an Omega on our keyboards (except for Antonis).

For the CLR, test your LED hooked up to a 10K trimmer (and a 1K resistor in series) to see what level of brightness you prefer.  Take into account low stage lighting, if that's where you'll play.  When you're happy, measure the trimmer and select the closest-value resistor for the CLR.  (Stands for "current-limiting resistor", btw.)  Don't use an online calculator: it'll tell you 390R and you'll be blind for the rest of the day. 

R7 is just setting the lowest amount of signal past the "sustain" pot.  It's part of a potential divider (with the pot).  Just having it there makes the minimum not zero.  But 560R as a proportion of 100K is almost the same (to your ears) as any other close-by value.  It's just not important.

Caps: if they will cope with your power supply and they'll fit on your board (and within your budget!), then they're OK.

I think perhaps you're overthinking things?  The problem with "best practice" is there's soooo many values of "best".  It's good to learn and understand, but even better to build and play music!   

[antonis]

And we use "R" because we don't have an Omega on our keyboards (except for Antonis).

Should a statement like: " I can easily use inverted Ω for transconductance " change you into a green-eyed monster, Marck..?? 

P.S.
To be more "dogmatic", use of "u" instead of "μ" for micro (0,000001) could also be confusing (somebody could be misleaded to an imaginary "ultra" unit..)

I set the choice of decimal point (. vs ,) as an extra argument..

[Dolmetscher007]

the "B or A" note on the pots is confusing. The controls will operate differently depending on which is chosen. That seems like an odd choice to let up to the builder.

Matt... thanks for the killer answer! It must have just been late last night when I posted this, because OF COURSE 100k and 100R are different by 99,999 ohms. I'm not sure how I didn't make that connection. I just saw it and immediately Googled, "difference between 100k and 100R resistors?" and about 3 articles in, I had read so many confusing responses, that I didn't know which way was up anymore. But this morning... Duh! Ha ha! So thanks man!

Same for the 2k7 vs 2.7k. I have def. been looking at a lot of schematics and BOMs over the last few weeks that look like a Xerox of a Xerox of a Xerox... so I totally get that one for sure.

For the CLR, test your LED hooked up to a 10K trimmer (and a 1K resistor in series) to see what level of brightness you prefer.  Take into account low stage lighting, if that's where you'll play.  When you're happy, measure the trimmer and select the closest-value resistor for the CLR.  (Stands for "current-limiting resistor", btw.)  Don't use an online calculator: it'll tell you 390R and you'll be blind for the rest of the day. 

This is great! Thanks man. I will def. do this. QQ.... when you say 10K trimmer... is a "trimmer" and a potentiometer the same thing? Total n00b here btw... in case you couldn't tell. ;-)

R7 is just setting the lowest amount of signal past the "sustain" pot.  It's part of a potential divider (with the pot).  Just having it there makes the minimum not zero.  But 560R as a proportion of 100K is almost the same (to your ears) and any other close-by value.  It's just not important.

So, even though 560R and 100k are 99,440 ohms apart in value... it really makes no real audible difference, and a designer might choose to leave that value as a range so that a builder could buy a new resistor, or possibly just use one that he already has on hand that falls within that 99,440 somewhere. Correct?  I'm sure it sounds like I'm being so detail oriented, but the reason for that is that I have zero resistors just sitting around. I am placing my very first order for anything in my life to build this pedal. I am ordering 10 or 20 of each of these components, so that I can begin to build up my on-hand stock of things. But for this first order, I def. do not want to get 1/4 into a build and realize I have to wait several days/weeks because I ordered the wrong .22 cent part.   (although... I'm sure that could happen anyway) :-)  But I gotta start learning somewhere, right?

I think perhaps you're overthinking things?  The problem with "best practice" is there's soooo many values of "best".  It's good to learn and understand, but even better to build and play music!   

Oh definitely! Trust me man, I am normally a total, "Just grip it, and rip it!" kinda guy! I do not enjoy dwelling in minutia and detail. It's not how my "he's a creative-type," brain works. But the older I get, the more at home I've come to feel with asking the question and reading the manual rather than just trying to look at the picture and go for it. :-)  And I really appreciate your help Bud! I wish I could repay you guys somehow! If you ever come to Charleston SC for a Beach or Historical Vaca... beers are on me!

[EBK]

I set the choice of decimal point (. vs ,) as an extra argument..

Let's just use both at the same time!

3;14159

[duck_arse]

2k7 = 2.7k. Sometimes it's hard to read the . On photocopies or whatnot, so the k is out in the middle to make it clear that 2.7k is 2k7, and not 27k

a long time ago, printers were idiots, they didn't know their R's from their e-bows.

to my mind, the european use of the comma [2,7k] is acceptable and unconfusable. good enough.

I just saw it and immediately Googled, "difference between 100k and 100R resistors?" and about 3 articles in, I had read so many confusing responses, that I didn't know which way was up anymore.

don't waste time out there - if'n you have a question, come here first, ask us. your "faq's" are coming along nicely thus far.

a trimpot or timmer is a potentiometer usually board mounted and with no "user operable parts" - no shaft to fiddle. it is used at build/commission time to adjust something once, and is then left alone for all time. it can be wired as a potentiometer or as a variable resistor.

[Kevin Mitchell]

OF COURSE 100k and 100R are different by 99,999 ohms.

[bluebunny]

trimmer:	potentiometer:
(set once)	(twiddle all night long)

[Dolmetscher007]

potentiometer:

(twiddle all night long)

Oh man... I'd violate some agreement I'm sure if I posted what I usually end up twiddling with all night long.

[bluebunny]

Oh man... I'd violate some agreement I'm sure if I posted what I twiddle with all night long.

There are other forums for that...   

[bluebunny]

BTW, I didn't respond to your R7 comment.  I think the reason it's there at all is to avoid silence.  This might be a problem for some people who think that a "sustain" control can't ever imply silence.  Frankly, it's a daft name for that pot, but it's been around a long time - it is what it is.  If you'd called it "volume", then zero output fully counterclockwise wouldn't trouble anyone's grey cells.  So anyway, R7 is just a "small value" to let some not-quite-silent amount of signal through to the next stage.

Now go and do some shopping.      (BTW, you'll find plenty of "what should I buy first?" threads to guide your first stocking-up exercise.)

And if there are beers involved, ask as many questions as you like!   

[Dolmetscher007]

BTW, I didn't respond to your R7 comment.  I think the reason it's there at all is to avoid silence.  This might be a problem for some people...

Ha ha ha!!! Man... When I read JUST this sentence (above quote)... I thought you were talking about ME. Like... Personally.

I was like... "I didn't post that just to avoid silence. I honestly was asking..." and then I read it through a couple more times and... ding!!! Oh man... I think I need to go chop some wood or do something very... large... and out there!!! I've been sorting through grids and filters for parts, and datasheets. :-)

Thanks guys!

And yes!!! Beers are a definite... if you can make the trip over from the UK. I used to live in Europe and spent quite a lot of time in the UK. Oddly enough, mostly I was not in places like London etc. But in Bath, Rye, Ipswitch, Stowmarket, and Bury St Edmunds.  But yeah... you make it over, and its beers on me. I'll even find you some of that Old Speckled Hen dishwater from over there. :-)

[bluebunny]

LOL - no, just me pontificating on the circuit design.   

[PRR]

> OF COURSE 100k and 100R are different by 99,999 ohms
> 560R and 100k are 99,440 ohms apart in value...

I was paying you $100. Now I pay you $100,000. Do you really say "$99,999 (or $99,900!) more!" You would probably say "A thousand times more!" The simple way to look at it: you can now buy a THOUSAND cars instead of one. Or a 1,000 room mansion instead of the 1-room shack. You don't really think "Where can I get 999 more cars?"

Amplifiers are largely about ratios. Sometimes large ratios. Start thinking in ratios.

I have no problem with 2.7k or 2,7K, until the copying errors get bad. OR like last year when my eyes were bad. 2k7 is clearer than a dot-smudge. Then how do you notate "0.1 Ohm" (often used in power amps)? 0r1 looks funny at first but will not be confused for 1 Ohm.

[Dolmetscher007]

> OF COURSE 100k and 100R are different by 99,999 ohms
> 560R and 100k are 99,440 ohms apart in value...

I was paying you $100. Now I pay you $100,000. Do you really say "$99,999 (or $99,900!) more!" You would probably say "A thousand times more!" The simple way to look at it: you can now buy a THOUSAND cars instead of one. Or a 1,000 room mansion instead of the 1-room shack. You don't really think "Where can I get 999 more cars?"

Amplifiers are largely about ratios. Sometimes large ratios. Start thinking in ratios.

I have no problem with 2.7k or 2,7K, until the copying errors get bad. OR like last year when my eyes were bad. 2k7 is clearer than a dot-smudge. Then how do you notate "0.1 Ohm" (often used in power amps)? 0r1 looks funny at first but will not be confused for 1 Ohm.

Ha ha ha!!! 100,000 - 100 = 99,999. My 3rd grade teacher just rolled over in her grave, and facepalmed.

[bluebunny]

Ha ha ha!!! 100,000 - 100 = 99,999. My 3rd grade teacher just rolled over in her grave, and facepalmed.

You should see my daughter's efforts at mental arithmetic.  She's an accountant...   

[amptramp]

OK, 100,000 -100 = 99,900.  This is the same as 100K - 100R which is 99900R.