# capacitor charge duration

hello everyone, I'm a beginner with electronics. I am trying to experiment with the charging and discharging of a capacitor. Each time it is charged, a led lights up. When charging the led emits a slight light. If I wanted a brighter light how could I do? Does it make sense to put a transistor in it to amplify the current?

i am not using codes. I am trying to use components on breadboard without arduino or similar

Show your schematic and try to describe what you are trying to achieve.

chucky831:
hello everyone, I'm a beginner with electronics. I am trying to experiment with the charging and discharging of a capacitor. Each time it is charged, a led lights up. When charging the led emits a slight light. If I wanted a brighter light how could I do? Does it make sense to put a transistor in it to amplify the current?

A little addition to your education. A capacitor is never fully charged or fully discharged. It's a time thing. Usually when the current into or out of a capacitor is reduced to about 95% of it's initial value, it is considered fully charged/discharged. Many circuits use a smaller percentage to indicate fully charged/discharged. All depends on what you are designing for.
Paul

RC time constant i.e. A 1000uF capacitor and a 1K resistor will discharge to 63% of the original voltage in 1 second.

The discharge curve is the opposite of an "ideal battery". It discharges quickly at first and levels-off the more it's discharged. And an LED will be "worse" because LEDs are non-linear with lower resistance at higher voltage. (There should always be a current-limiting resistor in series with the LED.*)

If I wanted a brighter light how could I do?

A bigger capacitor, smaller resistor, or higher voltage. (A bigger capacitor won't actually make it brighter but it might be flashing full-brightness too quickly for your eye to perceive it.)

Does it make sense to put a transistor in it to amplify the current?

Probably not... If you had a power source separate from the capacitor, then yes. But, there is only so-much energy stored in the capacitor.

• And if there is no resistor, a bigger capacitor is more likely to burn-up the LED.

The simple way would be to use the cap voltage to drive a transistor base resistor , controlling the current to the led connected in series with the collector, with the emitter to GND. (LED current limiting resistor in series with led).
Probably want to start with rather high base resistor values and reduce gradually, otherwise the led would be on all the time.

A schematic would be great; with component values so we can see what you are trying to do.

How to make a schematic you can post

If as I suspect you have the LED connected across the cap it will draw current and the cap will no longer charge up nce the voltage exceeds the excitation voltqage for the LED - about 2V.

You want the LED to turn on when the capacitor voltage reaches a predetermined level, correct?

If yes, use a comparator, the LM393 would be a good choice.

Are you going to tell him it's open collector ?

raschemmel:
Are you going to tell him it's open collector ?

Why? That is only a minor inconvenience. The input voltage range may be more limiting.

So far, it's all nonsense.