Basic electronics

Any recommendations for a web resource on how it all works?

Amps and volts and how they make music, that sort of thing. O' level physics was a long time ago and the one time someone asked a sound reproduction question the teacher replied that it wasn't an area that interested him. The joy of learning.

 

How it all works? You don't ask much...

 

www.play-hookey.com its basic but good specialy for a US site

 

Electronics For Beginners http://ourworld.compuserve.com/homepages/g_knott/index21.htm

Intermediate Electronics http://ourworld.compuserve.com/homepages/g_knott/index7.htm

Basic Electronics http://www.electronics-tutorials.com/basics/basic-electronics.htm

Electronics Tutorials : Over 120 individual electronics tutorials topics
http://www.electronics-tutorials.com

All About Circuits : Complete guide to Electronic Circuits http://www.allaboutcircuits.com

Capacitors : Introduction, concise and illustrated
http://www.uoguelph.ca/~antoon/gadgets/caps/caps.html

Capacitors : Picking
http://www.capacitors.com/picking_capacitors/pickcap.htm
Capacitor basics, Testing for impedance and distortion, Selection criteria to optimize sound quality

Resistor Colour Code, Tutorial http://www.uoguelph.ca/~antoon/gadgets/resistors/resistor.htm

Soldering, An Introduction
A short illustrated introduction to soldering
http://ourworld.compuserve.com/homepages/g_knott/elect3.htm

Soldering, Basic Guide
This guide will make you an expert!
http://www.epemag.wimborne.co.uk/solderfaq.htm

Electronics Club
Identify components, Read a circuit diagram, Learn practical skills
http://www.kpsec.freeuk.com

Lessons In Electric Circuits
Six individual volumes with printable versions
http://www.ibiblio.org/obp/electricCircuits

 

WM, BlueMax - thanks for that, should keep me quiet for a bit.

Isaac - when I get to T.O.E. I'll know where to come.

 

So, I've been getting on okay with this and at least I have an idea what most of the stuff means even if I don't always know what it does. There is, however a niggle that won't go away and that's AC conductors. It seems to be the one thing that is always a fudge, ie this is how we talk about it conventionally and it's too complicated to explain any other way.

For example, this from the Walrus site (I don't expect a detailed description there as this is from an otherwise very informative piece on single ended v balanced, but it illustrates the point).

The same is true, at least by analogy, of the mains supply. A 'live' and a 'neutral' wire (plus an earth). I understand about the potential of the neutral being zero and the live being + or - relative to this. I have a grip on electrons as charge carriers, drift velocity being different to propagation of signal, reversed polarity and so on. If a take hold of the live mains wire, current will flow through me to earth (no need to prove it empirically) but not if I take hold of the neutral (if the place is wired correctly!). So it is fair to say that energy is coming from the live but not the neutral.

What I can't find an explanation of is how electrical energy has a direction (if indeed it does) whilst it's carriers (electrons) have an alternating velocity (ie there is no one direction to drift velocity in an AC conductor). Was having a conversation at the weekend relating this to ripples in water, the ripple travels while the water stays put; water molecules are actually in eliptical motion as I understand it, and the ripple doesn't need a return path (unless it's reflected) so the analogy breaks down.
Having looked at some of the debate around audio cables it would appear that I am not alone in my lack of understanding of this area.
On the physics side I got as far as 'band' theory for electrons but felt I was getting further from the question rather than addressing it. So who knows about this ?

 

Those links BM has posted are good reads, he's posted them before on another forum although I forget which one......

You could always go back to school, seriously, I used this one in the early days;

http://www.kpsec.freeuk.com/

Dont laugh, its very basic but very good if you know nowt.

 

Ooops, sorry BM, just read your post again, oh well two mentions for Kelsey Grammer school!

 

Have been working my way through them and yes dug out my old physics text books as well. Only remembered yesterday that I took the mechanics option at the time, there's no reason any of it should have looked familiar after twenty years but much of the electronics stuff really is being read for the first time.

 

The problem with certain areas of hi-fi electronics is that theres quite a few 'grey' areas which lack science credibility. I have an uncle who is a Dr. of physics with electronics being a specialist area, he worked in industry for quite a while before being appointed the head of a physics department at a large uni, Ive run quite a few things past him and he's not been that impressed to say the least! Like you've said you often find more questions than answers with these grey areas. If you search university web-sites you'll find more than enough interesting reading.

 

Coda, unless I've misread your question I think you're conflating two things.

Voltage is potential, the potential to drive current through a conductor. When you grab hold of neutral, no current flows because you are at the same potential as neutral - because AC neutral is connected to Earth. So no current flows, and you live. Relative to the AC hot you are still moving at mains potential however...

To any (conductor/load) connected between 'live' and neutral' the potential difference swaps at 50Hz (in the UK); there is a corresponding current which flows, which also reverses direction at 50Hz. It's not that electricity has 'a direction' - it's just that charge moves to try to minimise potential difference. Le Chatelier's principle in action.

Of course if the load is not purely resistive (a capacitor or inductor involved) then there is a phase difference between the voltage change and the current change...and the maths gets interesting rather quickly

 

mmm A.C theory,hippys favourite topic at collage.

 

Was happy with all of this, maybe it came out garbled. Two things:

As I understand it, the 'neutral' is always at zero potential, the 'live' varies between +280V and -280V (are they appr. the right peak values here?) with respect to it, so in a sense neutral is positive with respect to -280 but the notion of pd 'swapping' could confuse (as in 'that could confuse a stupid person') (can't remember who said it.....)

Which infers that charge is moving from 'neutral' to 'live' for half the time, no problem with that, zero is higher than minus anything, but just checking.

What I hope to get to, this being a hi-fi forum, is an understanding (basic though it will be) of how analogue audio frequency signals are conducted, and AC mains seemed a useful analogy. I do realise that this is a huge topic and if there is further (off-site) reading to be suggested please do so.

 

You have to get used to the idea of pd's 'blowing and sucking' fairly gently but quickly, as its crucial to further grasping. Yes I agree with you, its all relative [like number lines in school maths] and -340v peak [ 240vRMS incidentally..], has the same effect as 340v peak its just wrt [with respect to] the directions of force and flow. Try a few mind pictures of alternative systems...for example:

In the UK example, the live has the potential peaks, and neutral stays at 0v..but its just one way to do it.
You COULD have -170v pk on wire A and 170v pk on wire B [and in 1/50th sec they would reverse]. This is a balanced system and has some benefits, not least being safety. The yellow transformer for power tools on a building site means that you only have 1/2 the maximum voltage to earth, reducing shock hazard.

Then I would try to see the CRUCIAL difference between:

a] using electricity as a source of power [where you need the ability to source plenty of volts and current simultaneously],

and

b] electricity as a signal, data or control CARRIER - where you are only interested in either a changing voltage {or current}. The other 'part' ie current {or voltage}, is simply a necessary side effect in any practical system.

Unfortunately, the guy who wrote some of those tutorials linked earlier does not seem to have made this quantum understanding leap.........

 

I wouldnt try to think that electrical energy has a direction.
Firstly, think power, not energy [energy is just(!) power for a time greater than zero]. Second, it's all just transducers converting one form of power to another: You turn the generator mechanically, the power 'flowing' through the wires puts a magnetic brake on the generator. You input more mechanical power to keep the thing moving etc. Resistive components turn volts AND current [you need both for electrical power] into other power forms: heat, light etc. Electrical power is useless in itself. It's just a useful way to CARRY eg: mechanical power [input to the generator in the power station], to your loudspeaker [mechanical]. For this system, electricity is used BOTH to transport the power AND as a versatile controller [eg analogue music signal]. Both are different uses for electricity.

 

Thanks Graham, the fog starts to clear slowly......

The other thing I am trying to keep in mind is the difference between systems which can observed/measured/described directly, eg mechanical waves such as sound, and those for which we use a model [often more than one] which fits the behaviour of the system even though we cannot observe/measure/describe it directly eg electrical signals, e.m. radiation etc, we can observe what they do but not how.
The problem [for me] is when practice contradicts the given model.
So amplifier~speaker cable~speaker seems to fit well. Amplifier has pd across output terminals which for convenience are + and - , cable is two identical conductors and speaker is a transducer which converts [AC] electrical signal into sound, swap connection over and speaker still works fine, though now out of phase with it's partner. Taking an overview of an analogue system:mechanical at the stylus, mechanical at the speaker, electrical in between and, yes, a signal has passed [as far as the listener is concerned] in one direction.
Single ended interconnects, on the other hand, throw up something different.
They have two non-identical conductors ie core and braid. Is the signal carried by both of these? Is there a pd between the inner and outer conductor? I realise that this is probably a case of looking in the wrong place, but the interconnect doesn't appear [to me] to fit the basic AC circuit model, ie it's DC that reverses polarity.

 

The braid of a single-ended cable is at the ground potential of the system, and remains there. Whether it's chassis ground or circuit ground (and thus isolated from the chassis) is another can of worms not worth getting into at this point.

In that respect the ground/return is like the neutral wire in your mains example. It stays at 0V.

The signal in the signal line will then vary in both positive and negative directions relative to the ground/return. Current will pass back or forth along the signal line. No current should flow in the ground/return. Currents in the signal lines, however, are very small indeed.

 

Thanks Isaac.

 

realy? are you aruing with mr Kirchoff?
the neutral is not at 0v its flotating just like the live,olny its connected to the world we dont feel it ,disconect all the star points on transformers and then tell me neutral ius at 0v in refrence to earth