Develop a "feel" for electronics

[PerranOak]

I am determined to learn electronics from the ground up and to be completely familiar with all the concepts.

It understand all the maths but it still doesn't give me a real "feel" for the concepts.

One writer I came across talked about thinking of the capacitors in a circuit as actually rising and falling (in space!) as a way of intuitively understanding what's occurring.

This is the kind of intuitive feel tha tI want to have.

Does anyone have suggestions as to books/authors/resources that could help here please?

Cheers.

[Gyro]

That sort of 'feel' comes from experience... and maybe to some small extent, just ability to visualize that way. From what I've observed some engineers never 'get it'.

The legendary Bob Pease maintained that the best way to understand things was to fix them when they broke. His book 'Troubleshooting Analog Circuits' is very readable and full of tips and lesser known wisdom on components and circuit behavior.

[IconicPCB]

Do not resort to a wet finger... might end up with more than a "feel"

[miguelvp]

There is always the Hydraulic analogy:

https://en.wikipedia.org/wiki/Hydraulic_analogy

[tggzzz]

There are very very very few people that understand all the concepts. E.g. I have heard of one person that was authoratative  on radar systems from the antenna through RF front end through signal processing to cockpit human factors, but I never met them!

The best technique is to pick a project, understand what are the important theoretical concepts and equations, then build it antest it to see where theory and practice do and don't match. Change some aspect of the design and predict the change in performance, and measure it again.

Then repeat with a different project.

[uncle_bob]

Hi

No two people ever learn things in the same way. Most Electrical Engineering is the application of established principles. Physics is the study of those principles. Applied Physics is the boundary between theoretical physics and the more engineering oriented end of things.

Each discipline is has it's own emphasis and it's blind spots. You can easily take the "routine" of any one of those areas and befuddle the practitioners in one of the other areas.

By far the best way to "get" this stuff in the fashion you are talking about is in a college or university setting. Quite possibly with a dual major.

That said, a far more practical way to "get it" is to build stuff and see what happens. Analyze the result and try again. You will have big gaps in your understanding. That's just something you will have to live with.

Bob

[f5r5e5d]

resistors, caps, ect. are fairly inscrutable to the naked eyeball (when working, not exploding) - so really you are developing mental modeling and model testing skills to guess where to put probe of multimeter or oscilloscope and then interpret what you're seeing on them means for you understanding of the circuit, mental model

schematic reading is critical - there are commonly occurring subcircuits that you grow to recognize, quickly categorize at a "circuit function" level



for quickly getting started with circuit understanding don't forget simulation - various free and commercial Spice derived circuit simulators with schematic entry gui and waveform viewers can help learn - of course some of the learning is about the sim sw, model limitations, program syntax...
but the ability to quickly change the circuit or part values, move, add probes and learn the waveform interpretation can give a big boost over just working on real world circuit alone

and as the math ramps up the software for that can help too Computer Algebra Systems, Numerical/Matrix Solvers - some useful free versions there too - but for Symbolic CAS the best paid versions are way ahead of any free ones I've tried

[rs20]

For me, the hydraulic analogy got me started. I'm not thinking about water anymore, but I still think about the electricity flowing around. But, as mentioned, everyone learns differently, you just have to learn using whatever resources help you understand best, and the intuition might follow.

[PerranOak]

Thank you all for the feedback.

I did use the hydro-analogy and this helped. However, I'm in a "mid-phase" where I think I get all that but have not yet progressed to the stage where I can view sub-circuits like sub-routines in a programme.

For example, I get the hydro idea about a capacitor but when there's talk of grounding one lead of the capacitor which makes the other lead drop to -Vcc and all that, I get lost! Another thing I can't get over (I think this is a physics vs engineering issue as mentioned) is the idea that current flow "creates" a voltage drop! This is talked of all over but I just can't "feel" it. I can only think of a potential difference creating a current not that a current magically flows then poof! a voltage is thereby created!

Maybe it's true that I am theorising too much and experimenting too little.

[rs20]

Well, if you have a pipe with a partial blockage (resistance), then force water (current) through it, the pressure (voltage) will be higher before the blockage than after. There's a traffic jam behind the blockage, if the pipe bursts, then it would obviously be before the blockage, etc.

The water analogy is not always brilliant, especially when there's no current involved. A capacitor tends to hold the relative voltage across its two terminals constant; if terminal A is at 5V at terminal B is at 0V, then terminal B is 5V lower than terminal A. If you set terminal A to 0V, terminal B tends to stay that 5V lower than terminal A, which makes it 5V less than 0V: negative 5V.

Having said that, the hydraulic analogy still holds for this case, although really to make that claim I use my knowledge of electronics together with the hydraulic analogy to know that fact about hydraulics, so obviously the analogy is not really helping there!

[Richard Crowley]

Current flow doesn't "CREATE" a voltage drop. A voltage drop is the RESULT of current flowing through a non-perfect conductor.

If you had a 1000 foot extension cord with a large load at the end, you can be sure that you won't see the same voltage out at the load as you started with back at the source.  The difference between the source voltage and the voltage out at the end is the "voltage drop".

But your "grounding one lead of the capacitor which makes the other lead drop to -Vcc" leaves me scratching my head, also.  I have a hard time learning things in the abstract, but can easily see how practical examples work. Do you have an actual circuit where you see this condition?

[Brumby]

I won't get into too many details, but I'll have a go at the two things you've mentioned.

1. The capacitor.  When a capacitor is charged up and is not in any circuit, there will be a DC voltage across the two terminals, which will tend to stay there (except for leakage - but let's ignore that for the moment and assume we are talking about a high quality one).

If you want to measure the voltage, then you have to choose a reference point and measure the voltage with respect to that reference point.  For a solitary capacitor, that means picking one of the contacts as the reference point and connecting your meter to that (usually the 'common' or black coloured lead).  It is generally assigned a voltage value of 0v because if you put the other lead of your meter on the same point, it's obviously not going to measure anything!  Now, having connected the 'common' lead of your meter to this reference point, you then take the other meter lead and touch the other contact of the capacitor - which will give you a reading on your meter of however many volts the capacitor is charged to.

BUT is the measured voltage positive or negative?  The answer is - it depends on which contact you used as your reference point.  Say we have 10v on the capacitor.  If you connect the meter common to the negative terminal (using that as the reference point), you will measure the other (positive) contact as being +10v - but if you use the positive terminal as your reference point, then you will measure the other (negative) contact as being -10v.

All voltage measurements (not just for capacitors) are measured with respect to a particular reference point.  (Often this is 'ground' or 'chassis' - but not always.)

2. Creating a voltage drop.  In one sense - this is stating the process a bit 'back to front'.  First you have to remember, there has to be a potential difference (voltage) from a supply (of whatever sort) for any current to flow.  Once you have a circuit that connects across this potential difference, the voltage around the circuit has to go from the highest voltage of the supply to the lowest voltage of the supply - so, in fact, those 'voltage drops' are already going to happen - just exactly where and how much they will be across each component in the circuit is the fun bit!

Lets take a simple case: a resistor.  A voltage drop 'appears' across it when a current passes through it.  (How much is defined by Ohm's law: V=IR.)  I think 'appears' is a better word than 'create' in this context for understanding - but electrical designers have a pretty firm grip on this stuff and might use the word 'create' - because that's what they meant to happen.

[retrolefty]

One writer I came across talked about thinking of the capacitors in a circuit as actually rising and falling (in space!) as a way of intuitively understanding what's occurring.

 Analogies can be very useful, however everyone's head is wired differently so you have to find what works for you. For capacitance I use the analogy in physics of a spring, a thing that can charge or discharge energy.

[Galaxyrise]

For example, I get the hydro idea about a capacitor but when there's talk of grounding one lead of the capacitor which makes the other lead drop to -Vcc and all that, I get lost! .

Which analogy are you using?  I prefer to think of a capacitor as a stretchy diaphragm in the pipe.  A pressure difference will flex the diaphragm until the force of the diaphragm pushing back matches the pressure applied to it.  I find this model has a lot in common with real capacitors (like water doesn't need to pass through the membrane for current to flow) and can even have the various real parasitics added to it.

So if you take a capacitor like that, and charge it up, you've now stored energy in the diaphragm which will exist even out of circuit (with the ends sealed, obviously.)  You could measure the pressure difference between the two sides.  If you now attach the high pressure side of the capacitor to your circuit's "0" pressure point, the low pressure side will still be "sucking" and create an even lower pressure region than "0".  The capacitor isn't "dropping" voltage, the negative plate is at a lower potential.

[Galaxyrise]

schematic reading is critical - there are commonly occurring subcircuits that you grow to recognize, quickly categorize at a "circuit function" level

This is a place I'm currently struggling.  I know the components well enough that I can figure a circuit out eventually, but something like the circuits inside a LM399 (bottom of page 6 on the datasheet) are prohibitively slow to understand. I even know what the reference section does, which should make it easier!

Are there common ways to facilitate building that mental pattern recognition? I feel like I want a desk calendar with a schematic a day to read.

[rs20]

But your "grounding one lead of the capacitor which makes the other lead drop to -Vcc" leaves me scratching my head, also.  I have a hard time learning things in the abstract, but can easily see how practical examples work. Do you have an actual circuit where you see this condition?

[Richard Crowley]

Ah, so you are talking about a voltage inverter circuit.
It is the design of the ENTIRE CIRCUIT that produces a negative voltage.
The simple connection of the 100 uF capacitor to ground does not "make the other lead drop to -Vcc"
It takes the other parts of the output circuit (the two diodes and the 22 uF capacitor also) to accomplish the inversion.  And the 555 is used only to generate an alternating (AC) signal.

Did you read the description on the page?
http://pencho.my.contact.bg/start/comp/555/scheme/555.htm

[PerranOak]

Thanks all, this is very useful.

As I begin a new area of "study" I like to develop a feel, an intuition really. Physical analogies, water, diaphragms, etc. are great.

Trouble is, I don't know when to let go - I tried to visualise a complex amplifier circuit as water flows, etc.!

However, I suspect that I have skipped or misunderstood some things. For example, a BJT current mirror: I can see how the current setting side works, I can see how the varying load side works but how does the first side transmit the "information" to the second side? Is it the small increase in base voltage - this varies very little from the 0.6-0.7V as both BJTs (npn) have grounded emitters. I'm definitely missing something!

It could be to do with this current-to-voltage and voltage-to-current converter idea. To me, this sounds like converting apples to oranges!

[TimFox]

Two elementary concepts I learned in day 1 of my first electronics course:
1.  The voltage across a capacitor cannot change instantaneously.
2.  The current through an inductor cannot change instantaneously.
This can give a feel for the function of capacitors and inductors, before one calculates more realistic cases with finite rates of change or sinusoidal variation.

[rs20]

For example, a BJT current mirror: I can see how the current setting side works, I can see how the varying load side works but how does the first side transmit the "information" to the second side? Is it the small increase in base voltage - this varies very little from the 0.6-0.7V as both BJTs (npn) have grounded emitters.

Yes. This is why the two NPNs must be well-matched, and why they are sometimes thermally bonded together.

[IconicPCB]

At the risk of bursting your bubble ( to use a water analogy) the feel comes from understanding.. understanding comes from study
study results in knowledge and the knowledge need s to become CRYSTALISED KNOWLEDGE.

Crystalised knwoledge is that knowledge which is the kind of knowledge possesed when quized about times tables.. you know 7 x 7 =49 kind of knowledge.

This means understanding the maths behind the physics and then compressing that knowledge into the "gut feel" kind of understanding.

So comit yourself to improving your theoretical knowledge. Let it become second nature and You to will have visions akin to Tesla's.

[orolo]

In order to learn, you must burn. Start small: resistors, caps, LEDs... passives offer little resistance (to the right voltage). Then graduate to actives: zap MOSFETs, crack JFETs, puncture BJTs, make SCRs explode, watch tubes implode. But don't get lost in the discrete jungle: while frying a tunnel diode, or any other member of a dying race, is an enlightening experience, even the the most purist gourmet indulges in a good MCU bricking from time to time. The moment you sit there, watching the smoke come out of some precious multibuck IC, you'll start to feel it. Burn your way up the food chain. By the time you burn your first 'scope, you'll most definitely feel it. BURN.

Just be careful, and don't burn yourself (or others) too much. Safety first.

[Kilrah]

Let it become second nature and You to will have visions akin to Tesla's.

Not sure that's a compliment, since from the references I have while he was clever in many ways he also seemed to lack the most basic understanding in fields that were extremely important to his endeavors, which caused all the trouble he had during his life...

[cobbler]

Current flow doesn't "CREATE" a voltage drop. A voltage drop is the RESULT of current flowing through a non-perfect conductor.

If you had a 1000 foot extension cord with a large load at the end, you can be sure that you won't see the same voltage out at the load as you started with back at the source.  The difference between the source voltage and the voltage out at the end is the "voltage drop".

But your "grounding one lead of the capacitor which makes the other lead drop to -Vcc" leaves me scratching my head, also.  I have a hard time learning things in the abstract, but can easily see how practical examples work. Do you have an actual circuit where you see this condition?

The side affect of a voltage drop is always heat of some sort, is that correct?

[MrSlack]

Not quite. Look at ideal capacitors and inductors as an example. They don't dissipate the energy but store it so there is a voltage drop yet no net  heat generation.

In real capacitors and inductors there is a small resistance however.