I thought to start this thread as a place to discuss Ohm's Law, Watt's Law ect. and the functions of basic components, as they certainly work together.
Personally, I don't hate math. Though, it sometimes seems to hate me. I enjoy puzzles and problem solving and is why I enjoy dabbling in diy circuits in my spare time. But there is alot to learn and I found out the hard way if you get "trigger happy" with the components without knowing some of the basic formulas, it can get costly! I burned up my pot! (Yes, we are still talking components )
So in another thread we were talking about how a limiting resistor, through Ohm's Law, would have saved me from that. My next question is can a limiting resistor be used for multiple components, or should one be used for each? From what I learned so far, I would think one would suffice since the "brakes" are on in the circuit. But, there I go thinking again! Dangerous things can happen! Lol! Thanks for all your help.

Okay, so you know V=IR and P=VI. That's the base.
Now you need to figure out how parallel and series works (it helped me a lot to think of current as flowing water - and a resistor as a partially closed tap) and visualize the circuit - if there is only one way for current to get to the circuit and that is through your limiting resistor, one is fine. If there is a way around that limiting resistor, you may need more or may need to choose a different location. You may not need or want to current limit all of your circuit.
See, the resistor doesn't care about its surroundings - it may interact with them, but it basically just, erm, resists. It makes no difference if there is a 1kOhm resistor behind it or a huge circuit that resists (or sinks, looking at it another way) current *just like a 1k resistor*. Net effect is the same.
Next (and this is where the fun really starts) is figuring out what Ohms law does with components that are frequency dependant. A capacitor can be seen as a resistance that varies with signal frequency. Below a certain frequency, resistance is high enough for the cap to be assumed an open connection (no current possible, like an open bridge), above a certain frequency the cap behaves like a closed connection. Where these frequencies are depend on the value of the cap *and it's surroundings*. Look up RC filter. Welcome to the party.

QuoteNext (and this is where the fun really starts) is figuring out what Ohms law does with components that are frequency dependant. A capacitor can be seen as a resistance that varies with signal frequency. Below a certain frequency, resistance is high enough for the cap to be assumed an open connection (no current possible, like an open bridge), above a certain frequency the cap behaves like a closed connection. Where these frequencies are depend on the value of the cap *and it's surroundings*. Look up RC filter.

I must say, it took me a while to get a handle on caps when I start putzing around with this stuff, and I wish someone had told me this a while back. It would have made it much easier for my brain to digest.

Excellent description Mike, thanks.

One thing that I used a lot while studying circuits at university was this idea:

1) At DC, ideal cap "isn't there" and ideal inductor is a short circuit.
2) At high/infinite frequency, ideal cap is a short circuit and ideal inductor "isn't there".  This also applies to a power on event, where voltage suddenly goes from 0 to 9 volts.

Few more:

Capacitors resist abrupt changes in voltage.

Inductors resist abrupt changes in current.

In between zero and infinity, things change, generally smoothly.

Sharp edges on waveforms indicate presence of high frequencies.

Symmetrical waveforms will have only odd order harmonics.

You will only get resonant peaks if there are either LC combinations or a structure like a gyrator which uses a gain element to simulate an inductor's behavior.  This might be getting a bit esoteric.

That is pretty much my "seat of the pants" perspective on circuits and signals and above that I tend to rely on math.

Just some random crap that might help:

If you have two (or more) components in series, the current through one is equal to the current through the other.  If they're in parallel, they split the current proportionate to their resistance.

All voltage is relative.

Vector math is fun, but you don't need it unless you're mixing Ls and Cs in the same circuit.

Most importantly:  Everything Useful is a Voltage Divider!  If you're just starting out, do yourself a huge favor and get this in your head now.  Learn to see how and why any group of components acts as a voltage divider and you're most of the way to analyzing any circuit you might choose.

was watching a video today that a transistor is just a voltage divider, resistor that changes - it got into saturation and cut off - the input and Vout going up and down with a resistor adding DC voltage ..with a cap ..lol I got lost ..biasing the input etc ...trying to learn from the beginning but this video might be a bit advanced ..thee main point he kept making was voltage dividing ..somehow the side benefit = amplification through transformation ..phase inversion..so what is Vcc?  I can see how the input goes in and then out - output voltage proportional to the input signal. showing an opamp with an infinite gain , and how it had like 25-30 transistors and resistors with one cap in the middle I/O


setting my bench to tackle the LPB1


I do not have a 100K lin but I have a 50K lin, will that still work or what else could replace teh pot there ?




maybe I need a nap , I have 3 going to my dc jack instead of my 1/4 star ground lol ...a nap then a few cups of coffee ololol

i do understand this now


Vout = R2/r1+R2 x Vin

the lower R2 is replaced by the transistor

Kirchhoff's Law

The Smith chart

** When thinking about current thru a circuit BRANCH - one complete path - it's helpful to go on ahead and add up all the R's in it.  In series, of course this is just the sum of the resistances.   Then, do Ohm's Law, and your current result is the current thru that WHOLE branch.  This goes with the above statement about "series runs have the same current thru the whole thing" - yes, as the sum of the resistances.

If the R's are in parallel, you have to do the product over sum:  R1xR2/R1+R2    For many in parallel, you are stick with 1 / 1/R1 + 1/R2.....1/Rn

Another 'big' hurdle, at least for me, was considering VOLTAGE DROPS, first by looking at series resistances...any good tutorial on Ohm's Law on the net should talk about this (Kirchoff's law, really)...works well with LightSound's comment above re. voltage division - each resistor is DROPPING voltage.  And his transistor is one of the resistances...when current is flowing thru a resistor or transistor, LED etc, there is a voltage DROP....this is why the signal from a BJT is inverted (common emitter)!  Current is increasing, yet voltage is decreasing, inversely....at the return of your circuit branch to ground, the voltage will be zero, as it was dropped by each circuit element.  
>> This boggled me for a while when younger because R1 may see 9V, but the next in order, R2, may only have 3V applied to it!!  Something to check with a meter and see for yourself...


** C's offer varying resistance based on frequency, essentially open at DC (they block DC) and decreasing in reactance (AC resistance) as freq increases.  The property we're looking at with C's is "Reactance", and probably should come a step after one has really gotten their head around Ohm, IMO!


Getting a chart for the wall like this one helps:  https://godofsteam.files.wordpress.com/2013/07/2000px-ohms_law_pie_chart-svg.png

** getting Ohm tight on DC only, then moving to how AC and AC with DC offsets works, may be the way to go, rather than trying to decode all of it at once.     The principles are exactly the same, but the 'material' you're working with has different properties.  

** Build, experiment, play around, measure, watch, learn...don't be afraid to - no, EXPECT to - burn a few things out.  At 9V and 10 cents each, don't worry about it    


PS - LightSound - yes, throw the 50K in there til you get the 'right' 100k pot.  It will "load down" the output a bit, but I doubt there will be a big sonic issue. Won't hurt a thing to use 50k temporarily.

Really helpful! Thank you guys! Is there a table like that for resistors?
Also, Gibson in the schem. U shared with me for the sine wave, how do I wire the transistors? I did some studying on them and understand there is an. emitter, base, and collector. Just not sure how to wire it up. Thank you for your patience in teaching this stuff. If its any consolation, Im hear to stay. I'm in it to win it!

Yep, a transistor amplifier works like a voltage divider.  Tubes do essentially exactly the same thing.  The tube/transistor is one of the resistors in a divider that splits the supply voltage to create our output.

A filter also is a voltage divider.  In a simple RC LPF, the capacitor takes the place of the "bottom resistor". Since it is very smaller at higher frequencies, the output for those frequencies is smaller.  In an HPF, the C is the "top resistor", and since it's bigger at low frequencies...

^  Yep. In fact, the -3dB 'corner frequency' you get by doing 1/2pi R C happens when the resistance of the R is the same as the reactance of the C 


Ok, here's another for ya, Bluez...http://beavisaudio.com/techpages/Transistor-Pinouts/
Print that sucker and put it over the desk!    I have one like that, the transistors and mosfets are smaller, so same page I did common opamp pinouts, the pin for the 555, a few needed formulae and pinout for the 12AX* series.    Gotta keep this stuff right in your face!  I have a "E/I|R" chart, too. 

In terms of attaching the transistor...get a 'blank' PCB perf board from Rat Shack or somewhere like that...you just pop the transistor in 3 adjacent holes.  You spread the outer legs a bit to "dress" it.   Fold the leads over underneath.   Attach connecting R's etc. to the leg, solder it up.   Idea is to not get the BJT too hot, so work quickly.   Just do it, doubt you'll kill it.

If it helps, mark the holes with 3 colors of ink for E, B, and C.   I used to use black for E and red for C, base nothing.   Don't forget when you flip to solder, it's backwards     On that PDF for R.G.'s oscillator, the pins are collector at top, base in middle, and emitter at bottom (emitter has the arrrow).     

Using the chart linked above, if you get some 2N3904's, you can identify which is which..note the flat side, it shows you how to hold it for ID....

Awesome! Thank you all very much. Going to get busy with it! Be back in a few to post my progress. Actually, Im working on my soldering chops now. Some innocent  alligator clips are feeling my wrath! Lol!

> can a limiting resistor be used for multiple components, or should one be used for each?

1) Yes.

2) Do not pinch pennies. It isn't worth it.

3) Do math and see what happens.

First-- before you ask the "multiple" question, you probably should get VERY familiar with the single-pot problem. Put 9V across end and wiper of a 50K pot. Or better- use round numbers, 10V on a 10K pot. What is the current and power when wiper is turned to 10K? (1mA, 10mW.) What is the current and power when wiper is turned to zero? (infinity, infinity.) What about at 1%, 100 Ohms? (100mA, 1,000mW.) When wiper is turned to 1%, how much of the "250mW" power rating of the pot can you really use? Look inside: only 1% of the $1-worth of carbon is really involved. So you should assume 1% of 250mW or 2.5mW. 1,000mW in 2.5mW worth of carbon is why it smokes (400X overload).

----

The multiple question:

Your city water comes-in on a 1/2" or 5/8" pipe so a fault in your plumbing will not suck all the water out of the mains and foil fire-fighting. You still have enough for a shower. Or a flush. Maybe a shower and a flush, though there's a small pressure drop. Now say you build three houses in your back yard and feed all three through your one 5/8" water pipe. If four folk try to shower at once they may only get a trickle. And if you built a car-wash out back the 5/8" pipe is not enuff for that, not even considering a shower too. (Yes, modern car-washes recycle more water than they pull from the street but ignore that.)

The electric power wire (and transformer) from street to your house, same idea. It is sized for very small voltage-drop when you pull 100 Amps, but also so that it will NOT pass 10,000 Amps if your house develops a dead-short. Of course the fuse/breaker will try to break the current, but practical-size breakers at 10,000 Amps don't trip, they explode; so drop-wires are sized to limit the dead-short current to something less. For other reasons, my drop-wire limits me to 875A dead-short. This works OK, but the lights dim when the pump runs. A slick alternative might be to add more drop-wires, one for lights one for pump one for dryer, so one load does not drop voltage for another load. ("More resistors", where the resistor is the inevitable resistance of a too-long wire.) However these "resistors" would cost $5K each, not 12 cents, so I put up with the dimming.

Quote from: ashcat_lt on May 03, 2015, 01:45:56 PM
Vector math is fun....

You've got a VERY nasty sense of humor, sir...

So I've been doing alot of testing. All of it very basic but necessary. Watching voltage drops with different resistors etc. Then I thought to build a super easy circuit with a transistor to get used to how it behaves.
https://www.youtube.com/watch?v=-td7YT-Pums&feature=youtube_gdata_player
I followed if to a tee except I used a 2n2222 instead. No luck. Can't figure out what I did wrong. Maybe someone can shed some light. Are those two transistors that different?

Wow, we're into transistors already?   LOL
   
It might now work with a 2N2222 because some components need to be changed, as that transistor has different characteristics than the 3904.  Some circuits, it's ok to sub in whatever BJT - some are more sensitive.

Start here, make some switch circuits, understand how the NPN is working.  Then how the PNP works (youtube is great for this stuff!).  Look around, you'll see that many things can be used to control the base (sensors etc), and the BJT can be used to drive a lot of different things.
https://www.youtube.com/watch?v=gEMBXxWKUS0

Base to ground, NPN is off.  Base to 9V<THRU A 10K OR SO RESISTOR, NOT DIRECTLY TO POWER SUPPLY>, it is on (any volts higher than .7, actually, but that comes later).    Insert 330R resistor and LED in the collector path, cathode towards collector, and it will switch on/off this way using a 2N2222A.     That is, 9V  >> 330R >>  LED >|-   Collector     with emitter grounded. 

Once you can do that, then you can start making some neat stuff like in the above vid.     The 3904 would also make it easier    

Quote from: bluzeyonecat on May 04, 2015, 05:30:40 AM
I followed if to a tee except I used a 2n2222 instead. No luck. Can't figure out what I did wrong. Maybe someone can shed some light. Are those two transistors that different?

No... you can consider them as general purpose NPN bjts (as long as it conserns to you specific circuit..), but I'm not sure if you placed the 2N2222 with correct orientation (E,B,C)

If yes, then maybe you've made either wrong wiring or some wrong resistor value...

I cant get that lpb1 to work and I wired it p2p straight up ..here we go again lol

Good idea for a thread but don't let it turn into "what to do when it doesn't work", which is, coincidentally, a sticky thread* that will help you learn a lot about electronics via hands-on making and testing and then proper question-posting. The gurus here will blow your mind with their individual and collective wisdom, and are often generous with their time, experience and humor and will answer questions and guide you - IF you do your homework**.  You'll probably learn a lot more about the type of electronics and technology you're interested in (audio, low voltage, state of the art circa 1969) that way then by rote-learning formulas.

Something to keep in mind - this forum is a treasure trove, but you have to search it with a search engine, like DuckDuckGo, and the command 'site:'. For instance, "transistor substitute site:diystompboxes.com". Most of your questions have been answered; do a little digging here first and you'll get more helpful responses.

*always at the top of the forum list, easy to find
**read what to do when it doesn't work to know what your homework is

> No luck.

What does THAT mean?

You didn't win the lottery?
Toilet overflowed?
You got blue smoke?
Your car ran out of gas on the way to the gig?
You didn't score after the gig?

*Describe what happened in clear detail.* That's the first step in any development.

> I used a 2n2222 instead.

Should work fine.

Maybe you didn't connect a battery? Or connected it wrong? Wrong pinout? Swapped IN and OUT connections? Didn't get the part legs firmly set in the breadboard? After visual inspection (many electric troubles are semi-mechanical), it is good to have a meter (since electricity is invisible).

Quote from: PRR on May 03, 2015, 09:04:08 PM(Yes, modern car-washes recycle more water than they pull from the street but ignore that.)

How do they pull that off? Rain barrels?

Quote from: garcho on May 04, 2015, 12:22:29 PM
state of the art circa 1969

LOL