4 newbees: intro to resistors

[gaussmarkov]

i have been working on another part of gaussmarkov.net, where i plan to build up explanations of components
and how they work together.  there are some links below for the first round: resistors.  writing this has helped
me to straighten a lot of things out for myself.  if it's helpful to some others, that would be gravy.

the level is newbee with some math.  so far just a lot of addition and multiplication.  but when i do capacitors,
i will explain some of the complex number algebra that is so handy for filters and trig functions.

the approach is to present a bunch of pages with topics that are cross-referenced, working up from some first
principles.  no physics or chemistry ... basically circuit analysis as i have come to understand it.  obviously my
understanding keeps changing and i will be updating things as i learn more.  i am not the expert--i am just trying
to share something that could help some others.

R.G.'s stuff has been a huge help to me.  i want to put that up front.  if you want to get it right, be sure to read
his material.  i have made quite a few links into his writing.  but, as you will see, i have not just rewritten what
he has already posted.  i have incorporated a lot of things from posts on this forum by dozens of people and
tried to link those in too.  also, any mistakes are totally mine.  i've tried to be careful but ... you know how it is.

that said, i would appreciate any comments, references, or corrections.  post them here or send me a note. 
here's an outline of the resistor stuff.  i have not linked it up yet,  so you have to use these links to get there.

• parts: resistors (appearance, symbols, values, ratings, more information)
• resistors: limiting current (ohm's law, inferring current from voltage, internal resistance, resistor for an LED, power)
• resistors: in parallel (kirchoff's current law)
• resistors: in series (kirchoff's voltage law, resistor order, voltage divider)
• resistors: pots (appearance, symbols, variable resistor, taper, values, ratings, more information)
• resistors: mods (variable resistors, pots)

all the best, gm

[markm]

Real NICE Job gm.....
I am so impressed with what you have done on your site and this tutorial you got going there is Excellent!
Job well done my friend!!
Thank you very much! 

[idlechatterbox]

That's quality work and quality writing Gauss.

You asked for comments, so here's a few, probably in the nit-picking category.

QUOTE:
"Resistors are also rated by power in watts. This is a value that should not be exceeded. In stompbox construction, people generally use 1/4 watt resistors. Larger power ratings are fine but, because the resistor cases are larger, will not necessarily fit on published circuit board layouts."

You mentioned that you were gearing this towards the absolute beginner, so I was thinking that if one knew nothing about resistors, this passage might be confusing. You state that the value should not be exceeded, but then say that "larger power ratings are fine...." The impression might be given that the only reason one wants to stay within the rating threshold is the physical need to fit everything on the PCB. Also, it might not be that clear which value and what "exceeded" comes to. I think I know what you're getting at, namely, that it's safe to use a higher threshold but not safe to go lower. But maybe a real beginner might not get that. Also, maybe some mention of the connection between wattage rating and ability to shed off heat? 

Also, where you mention the labelling of the resistors, you explain that the number of the resistor on the schematic has no real meaning. Although it's probably true that the numbering varies, there are at least some cases where knowing that number can be a real benefit, since it can give one a sense of where the resistor is on the physical PCB, or where it is relative to another component of the same type (e.g., R202 is rarely right next to R3). Being able to relate the schematic to the actual physical circuit location seems kind of important, so the number does not seem to be meaningless (which to my ears translates to "random" or "of no consequence"). 

Again, just piddly suggestions, so maybe it's just me. Great webpage so far. Looks like it's taken a lot of time, but will surely save others lots of it. 

[subversivepinko]

Thanks, very helpful intro for beginners such as myself.

[gaussmarkov]

Real NICE Job gm.....
I am so impressed with what you have done on your site and this tutorial you got going there is Excellent!
Job well done my friend!!
Thank you very much! 

thank you!    i appreciate the encouragement. 

You asked for comments, so here's a few, probably in the nit-picking category.

no idle chatter there, my friend.  thanks very much for your comments!   

i have made changes to try to improve things along the lines you suggest.  the resistor labels
are now described as

Usually, this label is a rough guide to where the resistor is located on a schematic or layout: 
you can expect to find R3 somewhere near R4.

and, besides clarifying the language on power ratings, i pointed to an example calculation that i
have on another page.

For an example of calculating power requirements, see the Power section of resistors: limiting current.

and now i have a new section on that page called Acknowledgements. 

i don't know enough about power rating and heat dissipation to write that up yet.  i will have to do some reading
and give that some thought.

Thanks, very helpful intro for beginners such as myself.

sweet.  that's the gravy.    thanks for the generous feedback and welcome to the wonderful world of diystompboxes.com.

all the best, gm

[idlechatterbox]

QUOTE from the page on resistors in series:
"If you need a 3K resistor but only have 1K and 2K resistors, you can make an equivalent circuit by placing a 1K resistor in series where a 2K where the 3K resistor goes."

Typo? Did you mean to say "by placing a 1k resistor in series WITH a 2k where the 3k resistor goes"?

While reading the page on pots (nice job there by way, the photos and diagrams should make everything clear), I was also thinking of a sort of interesting fact about them. Other than maybe batteries, pots have a unique distinction in that they are probably the only component that the average person has contact with (average being the normal person who doesn't tear equipment apart or build from scratch). Most people will live and die without ever touching an actual resistor or transistor, but anyone who's adjusted the volume on a car radio, dimmed the lightswitch, turned town the brightness of their computer monitor, etc. has touched a pot. Again, not a big deal in terms of explaining how the stuff works, so maybe not worth caring about.

Nice work so far. Can't wait till you get to transformers! 

[gaussmarkov]

QUOTE from the page on resistors in series:
"If you need a 3K resistor but only have 1K and 2K resistors, you can make an equivalent circuit by placing a 1K resistor in series where a 2K where the 3K resistor goes."

Typo? Did you mean to say "by placing a 1k resistor in series WITH a 2k where the 3k resistor goes"?

While reading the page on pots (nice job there by way, the photos and diagrams should make everything clear), I was also thinking of a sort of interesting fact about them. Other than maybe batteries, pots have a unique distinction in that they are probably the only component that the average person has contact with (average being the normal person who doesn't tear equipment apart or build from scratch). Most people will live and die without ever touching an actual resistor or transistor, but anyone who's adjusted the volume on a car radio, dimmed the lightswitch, turned town the brightness of their computer monitor, etc. has touched a pot. Again, not a big deal in terms of explaining how the stuff works, so maybe not worth caring about.

Nice work so far. Can't wait till you get to transformers! 

thanks!  typo corrected and acknowledged. 

of course you are right about pots.  everybody uses them.  i will have to think about how that could be used
to improve the pots section.   

re transformers:  i can't wait either!    but i am off to the woods for the weekend.   so
i hope you have a good weekend, too.

--gm