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Discharging effects

Discussion in 'General Electronics Chat' started by walters, Nov 2, 2005.

  1. walters

    walters Banned

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    Because AC currents have alot of different paths and AC currents are bi-directional and can reflect back to the input stages or around another path?
     
  2. bloki

    bloki Member

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    What is the purpose of knowing all the currents in circuit? It makes no sense.
    But knowing you hate mathematics and do not want to deal with it use some SPICE simulation programe. But try some knitting first.
     
  3. walters

    walters Banned

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    Because i want to know how the circuit work you have to understand the AC current polaritys, path ways, discharging bi-directional to know how electronic preamps,mixers,power amps etc work and how to read a schematic more in detail how the AC currrent go
     
  4. dave

    Dave New Member

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  5. bloki

    bloki Member

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    Understanding how circuit works requires much more than knowing all currents or voltages in it. Your way is wrong. It will lead you nowhere.
    But you must be able to calculate specific current or voltage. To do it you must use mathematics.
     
  6. walters

    walters Banned

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    I put my volt meter to test the Voltage
    Testing Current is way different because really which way is it going because Current is "Bi-directional" how do i know which way current is flowing? the Ampere meter doesn't have a "Direction of current flow" is just give measure's current

    Its really hard to measure discharging currents because of the amprere Current meter

    What is the Theory behind discharging currents and where do they go which paths?
     
  7. audioguru

    audioguru Well-Known Member Most Helpful Member

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    1) I don't even think about capacitors charging and discharging in AC circuits. The impedance of a capacitor at a certain frequency is important and is simple to calculate.
    2) The only reflection I think about is that an unbypassed emitter resistor of a transistor appears as an impedance to ground at the base multiplied by the gain of the transistor. Tubes are forgotten history for me.
    3) Preamps and mixers have a few coupling capacitors and it is easy to calculate their impedance at a certain frequency to determine their effect on low frequency roll-off. The same thing applies to capacitors across emitter resistors.
    4) Modern power amplifier circuits are direct coupled and don't use capacitors to couple signals except for an input cpoupling capacitor which has an impedance at a certain frequency which is easy to calculate.
    5) I don't look at AC current polarities because they don't exist. AC doesn't have polarity. NPN and PNP transistors have polarity which is easy to learn.
     
  8. DigiTan

    DigiTan New Member

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    bloki, take a chill. Hurling insults at everybody will not help the situation.

    Covering the bases for the AC circuits you described generally spans two or three college engineering courses. Because of this, I'd really recommend AllAboutCircuits because you need to know all of it just to get started with AC. This is really a matter for a new thread, but I can cover the basics if you have any specific questions on a circuit. walter, what is your math/electronics background? I mean are you familiar with applied calculus and mesh/node analysis, because those are essential to what you're asking for?
     
  9. bloki

    bloki Member

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    Current may have all sorts of waveforms. It can be pure DC, pure AC, it can have DC and AC component, it can have impulse shape, it can be periodic or aperiodic... Frequency of AC component can be from very low to extreemly high. So as the voltages.
    Your digital handheld instrument has a limited capabillity in this respect and can not serve you in the most of the cases. You should use oscilloscope with propper voltage and current probes. Some aspects of the signal can be observed by using spectrum analyzer etc.
    Knowing the amount of all currrents in a circuit will tell you nothing about how circuit works.
     
  10. walters

    walters Banned

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    Thanks guys

    Just alittle electronic math i know from my electronic book has electronic math formulas but this is very very basic to you guys im not that smart

    So what test meter would tell what direction Current is flowing in ?
    Because Current is Bi directional it can go anywhere in the circuit forwards, backwards, up and down and around
     
  11. bloki

    bloki Member

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    Just a comment.
    You are using FAQ method to collect partial informations about electronics. This is not the way to learn it. You will be more and more confused and you will have more and more questions.
    You must build your knowledge step by step from basics to more complicated matters. Knowledge must be build up not only collected.
    Finally you will not be able to see a forest because of trees.
     
  12. mstechca

    mstechca New Member

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    Why do you care?

    Walters,

    by now, please understand that NO ONE CARES ABOUT CHARGING AND DISCHARGING IN A CIRCUIT unless the circuit is specifically about it.
    in fact, as nigel said, IT IS POINTLESS TO SEEK INFORMATION ON IT.


    Buy a multimeter, and experiment with it.
    and go to your library and read a whole bunch of books.

    you can tell by the display. Ifyou see a -ve sign, it is flowing the wrong way. but, I was taught that current flowed from -ve to +ve. so how could it be bi-directional?

    It's better to understand it by looking at polarities. for example, the anode of an LED should go to +ve, and the cathode to -ve through a resistor.
     
  13. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    In which case you were probably taught 'wrong'?.

    Conventional current flow is from +ve to -ve, but electron flow is from -ve to +ve. Confusing, but it's that way for historical reasons as much as anything else. From a design or electronics point of view it doesn't really make any difference - you simply connect your meter the correct way round and it reads correctly.
     
  14. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Wrong! Many circuits use a dual supply with negative voltages and currents.
    A PNP transistor circuit frequently uses only a negative supply and all voltages and currents in it are negative.
     
  15. walters

    walters Banned

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    Thanks guys

    When measuring Current how do you know where to put the negative black probe and the Hot positive probe because if you switch them around it still measures the current but the polarity is different how do you know really which is the right polarity?

    Can someone please look at the schematics i posted on the hyperlinks and take a Red pen and draw "Arrows" showing me where the currents directions are and take a Blue pen and show me the Discharging currents please just have a bunch of Red and Blue arrows showing me the directions of the currents please
     
  16. bloki

    bloki Member

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    New facts. You do not use logic. When measuring DC you do not need to know the polarity of voltage, instrument will show it to you. If negative sign appears it shows that your prediction of polarity was wrong.
     
  17. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Why? Looking at charging and discharging currents and their directions is pointless. The only parts in a circuit that have charging and discharging currents are capacitors:
    1) Supply bypass capacitors charge the moment the circuit is switched on and remain charged until the circuit is switched off, unless the supply that continuously charges them is overloaded.
    2) Coupling capacitors charge the moment the circuit is switched on and remain charged until the circuit is switched off, unless the program's frequency is lower than their cutoff frequency.

    Instead, you need to know how the circuit's tubes and transistors work, then you will be able to "read" a schematic like a book. :lol:
     
  18. walters

    walters Banned

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    Thanks guys

    [/quote]When measuring DC you do not need to know the polarity of voltage, instrument will show it to you. If negative sign appears it shows that your prediction of polarity was wrong.


    But what about AC currents because its alternating?
     
  19. bloki

    bloki Member

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    Things may look more complicated. When we speak about charging or discharging of capacitors we have in mind exactly what audioguru said. But any change of current through capacitor is causing change of electric charge in capacitor and as consequence a change of voltage across it.
     
  20. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    You just use an AC meter! - you seem intent on making life very difficult for yourself?.
     
  21. DigiTan

    DigiTan New Member

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    walters, I'd really recommend getting all the DC fundamentals down first.

    AC is like is cold water: you've got to go in one step at a time. Trying to plunge in all at once is just unnessary torture. Engineers don't spend 4+ years in post secondary by accident.
     

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