How to know that which electronic circuitry requires which electronic components

Discussion in 'Embedded Systems and Microcontrollers' started by bobparihar, Aug 22, 2014.

  1. bobparihar

    Thread Starter Member

    Jul 31, 2014
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    I am doing college projects of embedded system.

    i am at beginner level in hardware, at some stage of hardware implementation i used to download the circuit diagram of a particular project.

    but i don't know why a particular grading of transistor or diode is used with the circuitry i just copy it.

    how to know why a particular diode or transistor or MOSFET etc is used in a particular circuitry.

    how to know these kind of basics?
     
  2. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    voltage and current

    If you pick wrong part, you apply voltage and current, then you see some blue-ish smoke, then you need new part.
     
    Metalmann likes this.
  3. bobparihar

    Thread Starter Member

    Jul 31, 2014
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    the idea u have suggested will waste my money and time
     
  4. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    You will waste money if you try to make something you do not understand.

    shteii01 did not gave you any Idea. I second what shteii01 said.

    It seems you need to know the theory on how to chose components before downloading a circuit and try to make it right on the first try.
     
  5. elabsp

    New Member

    Oct 23, 2013
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    Correct, you have to learn at least basics of electronics first before doing any implementation. Then after that you will able to learn with practical experience
     
  6. bobparihar

    Thread Starter Member

    Jul 31, 2014
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    at least give me some link of sites where i should learn or any type of study material or book u suggest me
     
  7. Metalmann

    Active Member

    Dec 8, 2012
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  8. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    As far as websites one very good one I know of is here.

    They even have a forum to ask specific questions.

    Do note that if you ask something akin to "how do I become a doctor" the best answers will be "go to doctor school."

    Do expect some fun to be had at your expense for asking such a general question.
     
  9. joeyd999

    AAC Fanatic!

    Jun 6, 2011
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    Invest in a copy of "The Art of Electronics" by Paul Horowitz and Winfield Hill. It's getting a little long in the tooth, but is still, IMHO, the go-to bible of basic electronics -- and it will take you almost as far as you want to go.

    The nice thing about the book is it gives you good theory and practical examples, as well as ways *not to do things* -- more important, IMHO, than ways to do things.
     
  10. Ramussons

    Active Member

    May 3, 2013
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    How are you doing a "College Project" outside your area of study?
    Which is the college that permits this?

    Or are you planning to do projects for others on a turnkey basis?
     
  11. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    Basically you are right.

    However, this approach of testing and observing result is also the root of Scientific Method.




    Let us examine a practical application.
    We have a bright how power LED. This LED has following parameters:
    * Forward voltage of 10 volts.
    * Current of 100 mA (0.1 amperes).
    We also have a 24 volt power supply.
    Now, we don't want to burn the LED (we probably did it before this attempt and already observed the blue-ish smoke). So. We will use a current limiting resistor.
    R=(24-10)/(0.1)=140 Ohm
    We take this 140 Ohm resistor and put it in series with the LED. AND we see blue-ish smoke first from the resistor. Hopefully the resistor burned through and created open circuit that saved our LED.
    What happened?
    Well... let us examine the resistor. We have resistor in series with led, the voltage across this group is 24 volts. We know that voltage across the LED is 10 volts. That means that the voltage across resistor is 24-10=14 volts. Now, the resistor is in series with LED, that means that the same 100 mA that goes though the LED also goes through resistor. This means that current through resistor is 100 mA (0.1 A).
    What is the power dissipated in the resistor?
    Power=14 volts * 0.1 amperes=1.4 Watts
    Now go back up. Did you see me derive 140 Ohm value of the resistor? Yes, you did.
    Did you see me say how much power the resistor needs to handle?
    No, you did not.
    So.
    Why did resistor go up in blue-ish smoke?
    It did go up in blue-ish smoke because we grabbed a chip resistor that we can buy for pittance and this resistor can handle 0.25 Watts (¼ Watts). By applying voltage and current to the resistor we in fact applied 1.4 Watts which is 5.6 times more power than what resistor is designed to handle. Therefore the poor little helpless and clueless resistor burned up and produced the blue-ish smoke.
    End of story.
     
  12. bobparihar

    Thread Starter Member

    Jul 31, 2014
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    I just cramme the circuit diagram. any project it would be i know about 40-50% of the basics that why a component is there.. but not all of it. and also i am somewhat good at software level of a project
     
  13. Ramussons

    Active Member

    May 3, 2013
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    Yep. Every child learns that "Fire" burns after getting burnt :D Thank God the op is not into ballistics :rolleyes:
     
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