capacitor

[meowth08]

Hello,

How do I know the kind of capacitor to use when I am given a schematic diagram of a circuit. I honestly do not know whether I'm going to use ceramic, electrolytic, mylar etc. Please educate me.

Thank you in advance.

 

[ronsimpson]

I don't know either. You need to give us the diagram! There are many kinds of caps and many uses.

 

[crutschow]

It depends upon the application and the required value. Here's a general discussion that may help.

 

[colin55]

Unless the actual description of the capacitor is given in the Bill Of Materials, the only way to work out the type and rating for the capacitor is from your own skills as an electronics engineer.
That's why you need to do a 2 week course to become a fully qualified electronics engineer.

 

[Parth86]

there are many kinds of capacitor like ceramic,electrolytic...............
it depend on the requirement of circuits
ceramic capacitor is useful when we need a low series resistance and low losses at high frequencies.

 

[ericgibbs]

hi m08.
Look at this pdf for useful capacitor info.

E.

 

[alec_t]

That's why you need to do a 2 week course to become a fully qualified electronics engineer.

You need more than that, Colin. You need many years experience.

 

[ericgibbs]

Unless the actual description of the capacitor is given in the Bill Of Materials, the only way to work out the type and rating for the capacitor is from your own skills as an electronics engineer.
That's why you need to do a 2 week course to become a fully qualified electronics engineer.

I think a two week course would be just enough to learn how to change a fuse, sounds about right.

 

[meowth08]

Hi,

crutschow and ericgibbs,

Thank you for the references you gave for me to read.

ronsimpson,

I'll try to upload the circuits later for you to see.

collin55,

Is there really a 2 week course to become a fully qualified electronics engineer? It took me longer than that to understand the concept of monostable and astable timer using ne555. Until now, I still have many questions unanswered and many more things to learn. 2 weeks for me will never be enough...

vead,

I don't understand this part of your post. "ceramic capacitor is useful when we need a low series resistance and low losses at high frequencies." Do you mean that ceramic caps give impedace and not pure reactance?

 

[colin55]

Every newcomer thinks it takes 2 weeks to learn about electronics.

After 40 years I know about 0.5% of electronics.

Even working out the correct type of capacitor for a particular application takes months, if not years, of experimentation and knowledge.
I fixed thousands of TV's that failed after years of service due to faulty capacitors.

Using the correct type of capacitor requires a lot of understanding and no textbook, course or web page has ever provided anything like the necessary facts.

For most applications, the type and manufacturer does not matter. But when it comes to high frequency, spike suppression, high voltage, ripple rejection, drift, etc, only experimentation and soak testing will find the solution.

The OP asked the one question that has never been answered.

You need to select each capacitor in a circuit and describe the type, what it does and why it has been selected. You can also talk about other types and why they are not suitable.
I have done this on my website but the information is scattered over the 20,000 pages of articles.
The best idea is for the OP to supply a circuit diagram and someone can discuss each of the capacitors and why they have been chosen.

 

[ljcox]

vead,

I don't understand this part of your post. "ceramic capacitor is useful when we need a low series resistance and low losses at high frequencies." Do you mean that ceramic caps give impedace and not pure reactance?

Yes, caps can have series resistance & inductance. They also have shunt resistance since no insulator is perfect - except perhaps a vacuum.

So the type of cap you need depends upon what frequency range you want the cap to operate over & various other factors.

The series resistance is called the "Equivalent Series Resistance" abbreviated as ESR.

 

[meowth08]

Len,

I have tried measuring the resistance of the capacitors i have at hand with an analog multitester. I set the tester in the ohmmeter function (x1), but did not see any deflection in the pointer. That's why I assumed that the cap is purely reactive and has no resistance. But thank you for the information. I know that the capacitor is made up of plates and between these plates is a dielectric which is an insulator. I agree that no dielectric is perfect .

collin55,

Is this the site you mentioned?? -talkingelectronics???

 

[colin55]

Is this the site you mentioned?? -talkingelectronics??? yes

 

[ljcox]

Len,

I have tried measuring the resistance of the capacitors i have at hand with an analog multitester. I set the tester in the ohmmeter function (x1), but did not see any deflection in the pointer. That's why I assumed that the cap is purely reactive and has no resistance. But thank you for the information. I know that the capacitor is made up of plates and between these plates is a dielectric which is an insulator. I agree that no dielectric is perfect .

In order to measure the resistance of the dielectric, you would need a meter that can read VERY high resistances. Analogue multimeters would have no hope, & a DMM is unlikely to be able to read it either.

Also, you need an ESR meter to measure the ESR.

 

[colin55]

You are not measuring the correct resistance.
You are measuring the "leakage."

A capacitor is like a miniature rechargeable battery.
When you charge a battery, current flows and the leads of the battery have a small resistance. Also the conductors inside the battery have a small resistance and these create a voltage drop.
The same with a capacitor.

When you charge a capacitor, the leads inside the capacitor and also the plates have a small resistance and these create a small voltage-drop.
They also limit the amount of current you can deliver and receive from a capacitor.

 

[WTP Pepper]

Unless the actual description of the capacitor is given in the Bill Of Materials, the only way to work out the type and rating for the capacitor is from your own skills as an electronics engineer.
That's why you need to do a 2 week course to become a fully qualified electronics engineer.

Two weeks!!!! I did 5 years and went into the industry and then I started learning....