Capacitors

Hello, I have a general question about capacitors. I understand that a capacitor holds a charge. I know that the more capacitance a capacitor has the longer it could keep an LED on, for example. I don't understand which capacitors I should use when. For example, what type of capacitor should I use if I had a 3.3V power supply and attached the capacitor to a 3.3V LED?

For starters, there is no such thing as a 3,3V led. You drive a led with a current and then there is a voltage drop across the led. A led ALWAYS needs a current limiting device and a resistor is the most simplest.

The 3,3V tells us you need a capacitor with at least a 3,3V rating + some headroom. 10V is kind of the lowest voltage rating of a normal capacitor. And that rating only tells the max voltage. So a 100V capacitor is as good at 3,3V as the 10V one. Only the 100V capacitor is much bigger then the 10V capacitor with the same capacitance.

As far as the capacity I can't tell you because you didn't tell us what you want to achieve with the capacitor...

I don't understand which capacitors I should use when. For example, what type of capacitor should I use if I had a 3.3V power supply and attached the capacitor to a 3.3V LED?

You should not use a capacitor in this situation at all.

Grumpy_Mike:
You should not use a capacitor in this situation at all.

Sort of. He does not NEED a capacitor to power a simple led, but he could play with caps and a led to see how different value caps work when he "pulls the plug" on the power. It might get boring real quick-little cap-led dims out fast, big cap-led stays on a little longer.

Considering he said:-

I don't understand which capacitors I should use when.

I thought he should know that the particular "when" he sited was not a "when" capacitors should be used.

Grumpy_Mike:
Considering he said:-I thought he should know that the particular "when" he sited was not a "when" capacitors should be used.

Understood and I totally agree. After thinking about it a bit, what I said would be a poor example of what caps actually do and are used for.