# Getting started in an Electronic Engineering Career

Discussion in 'General Electronics Chat' started by Shagon, Sep 27, 2010.

1. ### Shagon Thread Starter Active Member

Aug 19, 2009
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Hi I am 24 years old

Well I am worried that I am rather too old to get into an electronics engineering career since I have read so many people on this site have been in Electronics since their teenage years.

I am interested in Circuit Designing

I have done 4 courses in EET from excelsior college, Circuit Analysis 1 and 2, Electronics 1 and 2. I am not yet a student of the school yet but have plans too become one.

I leave in a small island in the Caribbean which doesn't have any Electronic industry what so ever, But have plans on moving to the states. The course that I take are Online base and I am rather worried that when I do move to the states that I would not have the required experience needed to get a job in the electronic engineering feild.

So I have decided on doing circuit designing as a hobby. So Yah I am a total Noob.

The first project I decided on doing is a crossover circuit I wanted to start small and eventually work my way up. Lol I wanted to do an Audio amplifier at first but thought that I am way over my head.

If possible I would just simply like someone of experience to guide me on my way as most time I feel like I am unsure of what I am doing.

Some one who I am able to contact and ask questions if possible... Lol I promise I wont be to much of a bother.. Thanks

Feb 17, 2009
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3. ### mbohuntr Senior Member

Apr 6, 2009
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Welcome aboard!! You aren't too old, I am 47, and just completed my AAS in electrical technology. My first career as a welder/fabricater ended with NAFTA. I should start as an electrical or I&C apprentice soon. Be sure your college credits transfer to a four year school.(If Excelsior isn't)

4. ### Shagon Thread Starter Active Member

Aug 19, 2009
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Ok well my first question..... I created a quick high pass filter using multism... with a 12vac source at 2000hz, an 80uF Electrolitic Cap and a 1ohm Resistor connected in series. When I measured the voltage across the cap I got approximately 8v and across the resistor is approximately 8v. 8+8 is 16. What I don't understand is how can the voltage across the cap and the resistor when added up together be more than the source voltage. I understand that the cap stores voltage but that's all that I can make out of it. Can any one explain this to me further if possible introduce some calculations.

5. ### Jony130 AAC Fanatic!

Feb 17, 2009
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First off all, in real life You should never connect an electrolytic capacitor to AC power source becaues It will explode.

And keep in mind that 80uF is not a "standard value" for a capacitor.
No one produce such capacitor, the closest value that you can buy is 68uF or 100uF.
http://sound.westhost.com/miscc.htm

Its quite simple, when voltage on capacitor is equal 8V the voltage on resistor reaches almost 0V.
And this is becaues when capacitor is full charge (act like open circuit) current in the circuit is 0A. So there is no voltage drop across resistor.
And when capacitor is empty (act like short circuit) there is no voltage across capacitor, so all voltages apply be voltage sources is apply across resistor.
So capacitor in ac circuit is charging and discharging in the rhythm of the input signal.
And this rhythmic charging/discharging of a capacitor is cause of a phase-shift between voltage on resistor and voltage on capacitor.
And thanks to this phase-shift we add voltages geometrically.
So we end-up withe this equation for AC signal $V_S=\sqrt{V_R^2+V_C^2}$

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6. ### Shagon Thread Starter Active Member

Aug 19, 2009
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Wow thanks alot.... lol guess I got a long way to go huh? hehehe
I knew that when the capacitor is full it acts as a open circuit and when it is empty it acts as an closed circuit but I made the big mistake of thinking that that only happens in DC circuits. In AC circuit however to make things simplier I decided to just picture the cap as a resistor whose resistance/impedance changes according to the frequency thats why I was so confused.

THANKS ALOT you were a great help....

7. ### mbohuntr Senior Member

Apr 6, 2009
431
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In filter circuits, caps are used as frequency filters, as well as to de-couple the DC component from the signal. Try some research on the subject of reactance. In short, capaciters will "resist" low frequencies, and pass higher ones easier. Inductors "Resist" high frequencies and pass lower ones easier. This produces "Reactance" measured in ohms. Combine this with the resistance, and this is "Impedence" referred to as "Z" Z= Xc+Xl +R

Xc = 1/2Pi F c
Xl = 2 Pi F l

8. ### Jony130 AAC Fanatic!

Feb 17, 2009
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Capacitor act the same in DC circuit as in AC circuit, the only difference is that, in AC circuit input voltage is constant changing.
When capacitor is full charged, then voltage on capacitor is Vin but current is 0A.
And when capacitor is discharge, and then start to charge-up, voltage on capacitor is 0V but current is at max value.
And that is why we say that capacitor voltage lags capacitor current by 90.
As for filter :

9. ### Shagon Thread Starter Active Member

Aug 19, 2009
48
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oh um Jony130
What I understand from the video you gave me about the electrolytic cap is that they explode when the polarities are connected in reverse but they can be connected to a AC power source right?

Don't they use them as filter capacitors?

10. ### Jony130 AAC Fanatic!

Feb 17, 2009
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No, If you have "pure" AC power source then electrolytic cap certainly explodes.

PS.
"pure" AC

Well, yes but we first need to charge the capacitor to DC voltage.

11. ### Shagon Thread Starter Active Member

Aug 19, 2009
48
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Hmmm Ok I understand....but with one question however.... I have seen cross over circuits with electrolytic capacitors. Are audio signals not considered pure AC? When you say pure AC do you mean that the positive and negative potential are always of equal magnitude?

12. ### Jony130 AAC Fanatic!

Feb 17, 2009
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The "pure" AC signal change his polarity every half cycle.
And electrolytic capacitors don't like revers polarities.
So you can not connect electrolytic capacitor to "pure" AC signal.

I don't think so, If you wont connect electrolytic capacitor to "pure" AC signal you need to use two capacitor connect in series.

Or you can use nonpolar capacitor.

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14. ### Jony130 AAC Fanatic!

Feb 17, 2009
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Shape does not matter

Yes, you can buy is and we and we call them bipolar electrolytics capacitor.

15. ### Jony130 AAC Fanatic!

Feb 17, 2009
4,577
1,281
Shape does not matter

Yes, you can buy them and we and we call them bipolar electrolytics capacitor.

16. ### Jony130 AAC Fanatic!

Feb 17, 2009
4,577
1,281
Shape does not matter