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Beginning electronics, understanding whats actually happening

Discussion in 'General Electronics Discussion' started by Ojustaboo, Jan 11, 2017.

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  1. Ojustaboo


    Jan 11, 2017
    Hi all. I understand what a capacitor does, I understand what a resistor does. What I don't understand and cant seem to find in books I've glanced at, is an explanation of how electronics works. I'm not talking about what electricity is, I'm talking about why I need the various components in whatever I'm building, and how the inventor/author worked out they were needed.

    Or to put it another way, I can buy a kit or follow a plan and build myself such things as (to name a few)

    FM radio
    audio amp
    valve amp
    audio delay
    Metal detector
    A rechargable clock
    A lighting dimmer
    A wireless baby monitor
    An electronic dice

    Where I'm getting stuck is how they actually work (how I would design my own from scratch)

    If I sat down with a pen and paper and nothing else, how would I go about working out what was needed and how it all works to build any of those (or anything else)

    Any good books or websites out there that answers this?

    Many thanks
  2. duke37


    Jan 9, 2011
    I have answered this type of question several times. Here we go again.

    Make yourself a crystal set, this will teach you about tuned circuits, their Q and ways of getting energy and out.

    Repair electric and electronic equipment. This will teach you logic, sadly often lacking and enhance your manual skills.

    Contact the RSGB for details of their Foundation courses. You may have one in your area. The examination is for the first stage of the amateur radio licence but you do not need to go for this. It will tell you what the components are and what they do. Some practical construction will be involved.

    I would not recommend a valve amplifier until you know a lot about the dangers of high voltage.
  3. KTW


    Feb 22, 2015
    Build something simple you have an interest in.
    Find a schematic on line or ask for help building the one you want.
    Post your questions and someone will usually respond.
    Ojustaboo likes this.
  4. darren adcock

    darren adcock

    Sep 26, 2016
    Thanks Duke27. I hadn't come accross rsgb. I will be in touch.
  5. darren adcock

    darren adcock

    Sep 26, 2016
    I found learning motor based circuits really useful as the motor offers a mechanical expression of what's going on. I leanred more in a couple of months of learning to control motors than a long time tinkering with audio circuits. I found this informed my understanding of electronics circuits.
    Ojustaboo likes this.
  6. BobK


    Jan 5, 2010
    How to learn about active electronic components:

    1. A diode is the simplest. Learn how it is used to rectify AC to DC and how it is used to combine logic signals.
    2. Next, learn about the bipolar transistor. First as a switch, then as an amplifier, and finally as an oscillator.
    3. Next learn about logic gates using transistors.
    4. Learn about the multivibrator, a simple 2 transistor circuit that can make an oscillator (astable multivibrator), a timer (monostable multivibrator) or a flip-flop (bistable multivibrator) which is essentially 1 bit of memory.

    Once you understand those basic circuits, you could build most anything out of combination of them.

    FETs and MOSFETs are similar to bipolar transistors and can do pretty much the same things, with different tradeoffs.

  7. Wayne Phillips

    Wayne Phillips

    Jan 7, 2018
    Above all never rush as it all takes time!
  8. kellys_eye


    Jun 25, 2010
    If you want to design your own circuits then you need to know and understands the FUNDAMENTALS of electricity and electronics, for which I can highly recommend the 'Horowitz' book.

    Expensive? Yes. But probably the ONLY book you'll ever need.....

    For most people this takes years to accomplish - college, university etc but it still possible to design circuits using building blocks - where the fundamentals are encompassed in a 'black box' type of module and all you do is enable the interfacing between them to build a completed device.

    In terms of modern electronics, this is often achieved using the Arduino (as a typical example, not a 'definitive' solution) whereby those modules are readily available PLUS the software is already written (for the most part) to interface to them.

    In this way you derive - from your basic idea - what it is you want to achieve, select the modules necessary to achieve the end result, connect them accordingly and write the software to bring it all together.

    This is the way the world is moving - to a modular form of construction, controlled by software. It is generally a digital environment with an emphasis on programming and a (smaller) understanding of the BASIC principles of the various modules you can choose/use.

    If you wish to approach electronics from an analogue direction then basic principles are unavoidable and, by its very nature, time consuming and (occasionally) maths intensive.

    Whilst adopting the 'learn how each active component works' approach will get you there, if you want results you can see/handle and appreciate you might aim towards the digital/modular route first to gain the encouragement the final product can give and THEN investigate how each module does what it does if the mood take you.

    In this day and age, it's not HOW a circuit works as to WHAT a circuit needs to do that ends up in development and, ultimately, manufacture. i.e. the IDEA is more lucrative than the solution - if that's your aim.
    Arouse1973 likes this.


    May 20, 2017
    Agreed, the Horowitz book is essentially the trade bible.
  10. Quifianie


    Jan 16, 2018
    definitely yes! unfortunately, it was too difficult to understand all of these, when I was a student and today it's a little bit hard, but I like it and I try to figure out
    anyway, thanks a lot for the book recommendation!
  11. Quifianie


    Jan 16, 2018
    just purchased this book and I like it already!

    “Without education, we are in a horrible and deadly danger of taking educated people seriously.” ― G.K. Chesterton,
    if you don’t have time or inspiration to write a quality essay, feel free to ask for help and get the highest grades!
    Last edited by a moderator: Mar 4, 2018
  12. Wayne Phillips

    Wayne Phillips

    Jan 7, 2018
    It also depends what feild of electronics your studying.. say from tv and video to radio and pa systems there is so much to learn.
  13. jilfe


    Sep 23, 2017
    "If I sat down with a pen and paper and nothing else, how would I go about working out what was needed and how it all works to build any of those (or anything else)"

    Here is a way to learn the very basics of getting started in transistor circuit design.
    First you need to be able to bias a transistor on to use it in a circuit.
    Here is a good practice learning on how to do it.

    The parameters found on a data sheet, they are given as typical values.
    They are only approximate values, and designing transistor circuits, is all about making the circuit perform reliable, nondependant of those component parameters.

    This will teach you how to simply calculate approximate values for the resistors needed to bias a transistor.
    Biasing a transistor is very necessary when designing transistor circuits, it allows you to set its working properties, wether it is an amplifier of current or voltage or a electronic switch.

    Voltages are refrenced from a ground point, in this case the negative side of the supply.
    The component designations are the choice of the designer.
    Every schematic has its own designations.

    In this schematic:
    VCC = the supply voltage.
    VC is the voltage at the collector of the transistor, refrenced from ground, (neg. side) of the supply.
    VE is voltage at the emitter term. ref. to ground.
    VB is the voltage at the base term. ref. to ground.
    VBE(sat)* Base-Emitter
    Saturation Voltage:
    Minimum = 0.65V

    To bias this transistor so it has 1/2 the supply voltage at its collector would be written as
    " VC = VCC/2"

    VC=4V. Meaning 4V is dropped across Q1 and RE from ground.
    That leaves the remaining 4V to be dropped across RC.
    Using ohms law is very extensive in designing transistor circuits.
    So (4V / RC) = IC where IC is the current flowing through the transistor on the collector emitter side.
    (4V / 10Kohms.) = 400uA. = IC.
    This same current is in the emitter resistor RE as well so now we can solve for RE.
    There are several ways to choose a resistor value for RE, in this example make the voltage VE across RE be around 1/3 of VCC.
    "VE = VCC/3" ~= 2.7V and "RE = VE/IC"
    Therefore "RE = 2.7V/400uA" = 6.6K ohms, choose a value available close to it, 6.65K ohms would be a good choice.
    There can be extensive calculations involved in solving for the base biasing resistors, for extreme accuracy in choosing component values, however most of the time to bias a transistor it is not needed, except in extreme cases, so the best way to approach this biasing scheme is to calculate ballpark (first approximation) values, then tweak them in the protobuild.

    Therefore RB1 can be calculated as 10 to 20 times RE. So choosing 10 times RE would be "RB1 = 10RE" = 66.5K ohms.
    Now we look at the data sheet above and see:
    VBE(sat)* Base-Emitter
    Saturation Voltage:
    Minimum = 0.65V

    So use that value to calculate the base voltage required.

    the equation to solve for base voltage is "VB = (VE + VBEmin.)" = (2.7V + 0.65V) = 3.35V = VB
    Now there is a base divider current "Idiv. that needs to be solved for so RB2 can be calculated.
    "Idiv. = (VB / RB1) = (3.35V / 67K ohms) ~=49uA = Idiv.
    Now this equation can be used to solve for RB2 value needed to bias the transistor to the set value chosen in step one.
    "RB2 = (VCC - VB) / Idiv.) = (8V - 3.35V) / 49uA ~= 94K ohms a 95.3K value could be chosen.

    Note:The resistor values are the ones available in LTspice:
    As always,protobuild it and tweak any values as needed.
    biasing 1.jpg

    Now apply a small signal of 1KHz at 100mV to it and see what voltage waveform is produced at its collector terminal, referenced to ground.

    biasing 1signal.jpg

    The input signal is 200mV pk-pk and the output signal is 294mV pk-pk. That's a Voltage gain (Av) of (294 / 200) = 1.47 = (Av).
    NOTICE: the ratio of the collector branch where we have (R1 and R2) they are designated as RC and RE, if we divide RE into Rc we get close to the same value. (RC / RE) = (10K / 6.65K) ~=1.5, this is very close to the Av calculation.

    That's because the value of the RC and RE can be chosen to design for a specific gain.
    Lets say RC has to remain at 10K for proper impedance matching, but we can change the value of RE to give a specific amplification gain.

    Try to achieve a voltage amplification of around 10 times the input signal.
    Redo the calculations keeping VC at 1/2 of VCC as before for symmertical output.

    Only now to solve for RE use the Av factor instead of the emitter voltage as used before.

    Av = (RC / RE) so rearranging "RE = RC / Av"
    RE = 10K / 10 = 1K ohms.
    Because RE was changed, that will also change the emitter voltage as well so new values for RB1 and RB2 need to be recalculated.
    IC is still the same since RC was not changed, therefor VE is now (400uA x 1Kohms) =0.4V
    VB is now (0.65v + 0.4v) =1.05V

    make RB1= (10xRE)= 10K ohms
    now (Idiv = (VB / 10K)= (1.05 / 10K) = 105uA.
    solving for RB2 gives {(8v - 1.05v) / 105uA} ~=66K ohms. 66.5K is available.
    Now protobuild it and see how it works.

    biasing 2.jpg

    So the DC bias voltage at the collector is good at around 3.97V.

    biasing 2signal.jpg

    And the Av is showing (1.856V p-p / 0.2V p-p) ~=9.28 very close to the ratio of RC/RE of 10.

    This is an introductory of what's involved in transistor circuit design.
    I gave you the very basic of basics, in this, once you can understand how to bias a transistor you can then advance to designing small signal amplifiers, power amplifiers digital circuits and the like, but first you need to learn how to turn on a transistor how to apply it in different classes of operation, also the 3 configurations CE, CC, CB, and switching characteristics as well as amplifying ect..

    There's a lot of good utube video teachings on transistor biasing and designing small signal amps and switches.

    Hope this helps in getting started learning this from the very basics.
    Last edited: Jan 26, 2018
  14. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Of course (and I think it's been mentioned earlier) it all depends on what you want to learn.

    "Everything" is pretty much not an option. There's so much that if you waited until you did know everything, you'd never get to do anything.
    • If you're interested in radios, then building a crystal radio might be a good first step.
    • If you're interested in amplifiers then learning to bias a transistor might be useful.
    • If you're interested in digital electronics then maybe a simple counter or sequencer.
    • If you're interested in microcontrollers then maybe grab an arduino.
    Whatever you do first, you'll find that there are both more advanced, and more fundamental things that you might need to know.

    Follow what you're interested in, but don't try to take steps that are too big or too small. Challenge yourself a little so you don't get bored, but don't step so far ahead of yourself that you get lost.

    edit: Major caveat! There's lots of erroneous information out there, and basic explanations often gloss over important details that are left for later. Be careful to check your sources and be prepared to refine your knowledge.
  15. Ratch


    Mar 10, 2013
    What is your problem? There is a multitude of books and web resources that teach and explain electrical science, both theory and hardware. Why do you have a hard time understanding what is taught? Others have learned it, why can't you? Can you learn other subjects? Do you have a hard time concentrating or have some other learning disability? Until you find out why you can't learn, we cannot help you.

  16. Wayne Phillips

    Wayne Phillips

    Jan 7, 2018

    Building something from a book or website can be a little confusing as reading or understanding what the diagram drawing is.

    Basic ohms law to help you work out what type of resistors to use and there power rating must never be pushed to hard!

    If you wanted to build a audio amplifier just to see how things work..a simple tda2030 chip will do. It gives 10 to 18w and can be powered by 12 to 25vdc.

    Now are you able to use a multi meter to check voltages?

    Leave big amps until you sure what your doing of as electric shocks can and will kill!
  17. Ratch


    Mar 10, 2013
    Are you giving advice to me or the OP?

  18. Wayne Phillips

    Wayne Phillips

    Jan 7, 2018
    That chap who's having trouble getting he's head round basic electronics..

    Ojustaboo... as I was reading the comment.
  19. dante_clericuzzio


    Mar 28, 2016
    Books only inspire you ...but the real knowledge in electronic is doing it..the books is not perfect and if you read too much you could wasted so many years of your life without doing a thing. I just started with a small circuit to step up voltage and still keep learning


    May 20, 2017
    Have to disagree with post #18. You have to do the basics first. If you are not prepared to go to classes to learn then buy the Horrowitz book. You do not need to read the entire publication before you start playing but, you must learn the basics first.
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