How do different electronic components make something "work"?

I've been trying to learn electronics and arduino. The one thing I don't get is when do you need a transistor or resistor or capacitor. I know that Resistors add resistance and what not but when do you decide to add things to the circuit? Like why do I need a resistor on LED's and so on. why can't I just connect it. I feel like I might understand but I need someone to really make the connection for me. I know its a pretty stupid and noobish question.

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canucksgirl5 years ago
There's an excellent Instructable here that explains Basic Electronics and should answer all of your questions. The author did a great job of breaking everything down into easily understood steps. :-)
thekendall (author)  canucksgirl5 years ago
yes, i have read that but I don't understand why I need each component. Why do I need a resistor for an LED? Yes, to increase the resistance but why does the resistance need to be increased?
Well, for a detailed answer... refer to this information.
thekendall (author)  canucksgirl5 years ago
SO this is what I think the connection is which makes sense. Correct me if I'm wrong but. The reason for putting a bunch of what seems to be useless circuits is to give the correct current charge etc. for a specific component? So we are just modifying the electric current going through the circuit?
Imagine that the current is like water flowing through a tube. If you push too much current through to a component (like an LED), it will burn out much quicker. So you use a resistor to prevent that.

If you look at the link that Re-design gave you, its to LED Calculators that you can use to figure out what resistor(s) you may need for your project. You'll need the information off the package for your LED's.
In the majority of case you are using the transistor as a switch. You need to do this because the microprocessor can only pass a small amount of electricity and what your connecting to it (motor, lamp etc) may well need more to operate (more electricity = more power)

If your just connecting a low power device such as an LED then you can often drive that directly from the microprocessor.

The output limit is generally around 20 milli amps (20/1000 Amp)

Re-design5 years ago
An led takes a certain amount of voltage to light up. That's called forward voltage.

If you power an led with it's forward voltage exactly then you don't need a resistor.  But mass produced leds vary some.  they won't all light at the same exact forward voltage.  So a resistor is used to provide some protection from overpowering the led.

If you are trying to power a 3 volt led from a 5 volt source then you must use a resistor to reduce the voltage and current to the level that the led can handle.  You can use an led calculator to figure the resistor to use.

If you are powering more than one led from the same voltage source you should use resistors since leds vary slightly from each other and one of the leds may end up taking more of the voltage than the others and burn out.  This then leaves more power for the others and and cause others to fail then they all end up failing.  Resistors here would help limit the current to each led so that none of them get more than they can handle.

Transistors, tubes, capacitors, coils, and resistors all perform different functions.  It depends on how the circuit is setup and what you are wanting the end result to do.  It's going to take some reading and experimentation for you to learn what they do and just as important - how to make them do what you want.  Google "electronic tutorial" and get started.