# Know nothing, need some help with capacitors

#### coder617

Joined May 9, 2020
4
I have an idea and would like to see if I can get some help hashing it out. The first part of my puzzle is what I hope is an easy question. I am not an engineer and know very little about electronic principles. So my question, is there a type of capacitor (or other item) that will accept a charge quickly and then give that charge out slower than it received it. So for example, a capacitor accepts its max charge in one second, then dissipates that charge in two seconds. Not looking for a solution that would involve any logic or complicated circuitry, just a simple, give it power and then get it back slower than you gave it.
Hope that makes sense and thanks for your feedback!

#### Audioguru again

Joined Oct 21, 2019
3,007
In your example of charging in 1 second then discharging in 2 seconds. Simply make the discharge current half the charge current.

#### Wolframore

Joined Jan 21, 2019
2,267
It’s done through current steering

#### sparky 1

Joined Nov 3, 2018
497
I had a (wall wort) a plug in power supply. It had an led that stayed on for several seconds after being unplugged.
The older wall worts had linear supply arrangement with filter capacitors. The (1000 uF) electrolytic capacitor also stored energy.
The resistor (470 Ohm) kept the led powered for several seconds because the capacitor was holding a charge measured in Farad units.

Lets say you purchased 2 each 2.7V 400 Farad capacitors then, using safety practice you charged it.
Could you plug it in briefly then go charge your cell phone slowly for \$2 in parts ?

#### coder617

Joined May 9, 2020
4
In your example of charging in 1 second then discharging in 2 seconds. Simply make the discharge current half the charge current.
I wouldn't even know how to order a capacitor this way. I'm afraid I need some elementary hand holding here.

#### Audioguru again

Joined Oct 21, 2019
3,007
You said "No Nothing Nobody" but you should have said "Know Nothing" then I would not have answered.
Because I am not a teacher and I like chatting with my peers.

#### Veracohr

Joined Jan 3, 2011
750
I have an idea and would like to see if I can get some help hashing it out. The first part of my puzzle is what I hope is an easy question. I am not an engineer and know very little about electronic principles. So my question, is there a type of capacitor (or other item) that will accept a charge quickly and then give that charge out slower than it received it. So for example, a capacitor accepts its max charge in one second, then dissipates that charge in two seconds. Not looking for a solution that would involve any logic or complicated circuitry, just a simple, give it power and then get it back slower than you gave it.
Hope that makes sense and thanks for your feedback!
The rate at which a capacitor charges and discharges is mostly determined by the charging/discharging circuit, not the capacitor itself. The only spec of the capacitor that would limit the rate is the Equivalent Series Resistance (ESR), and barring certain specialized types, this is generally pretty low.

#### sparky 1

Joined Nov 3, 2018
497
go to ebay type " 2.7V 400 Farad capacitors "
Initially it might be safer to use C cell batteries to charge the capacitors in series. Check them with multimeter.
If the capacitor bank is fully charged 2.7+2.7 = 5.4 Volts
because the voltage will drop you might use 3 capacitors fully charged 8.1 Volts @ 1200 Farads.
it is better to use leds and a 5V regulator like a 78L05.

Current steering, yes. We used current limiting diodes interacting with the world of small scale in order to get precise.
The current regulating mechanisms have systems. The terminology common to our instrumentation therefore our scale.
The emphasis is on small to large scale conversion, electricity can have enormous scale.

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#### #12

Joined Nov 30, 2010
18,217
This is kind of an expansion on what Veracohr said.

Capacitors are designed to have the smallest possible effect on charging rates. (They don't limit their current rates unless you are getting into some rather advanced stuff about high current or high speed.) You manage the time with resistors. If you want it to take a second to charge, you slow down the current with a resistor. If you want it to discharge slower, you limit the current flow with a resistor. If you want to have both circuits available at the same time, you use a diode in series with each resistor; one to allow current into the charging resistor and another diode to allow current to flow out the other resistor.

#### coder617

Joined May 9, 2020
4
This is kind of an expansion on what Veracohr said.

Capacitors are designed to have the smallest possible effect on charging rates. (They don't limit their current rates unless you are getting into some rather advanced stuff about high current or high speed.) You manage the time with resistors. If you want it to take a second to charge, you slow down the current with a resistor. If you want it to discharge slower, you limit the current flow with a resistor. If you want to have both circuits available at the same time, you use a diode in series with each resistor; one to allow current into the charging resistor and another diode to allow current to flow out the other resistor.
This is actually what I needed to know and was very easy to understand, thank you!

#### coder617

Joined May 9, 2020
4
If I wanted to charge a capacitor using 12V to its maximum capacity in 1/4 of a second and then have it dissipate that energy in 3/4 of a second what capacitor and diode combination would I need?

#### Audioguru again

Joined Oct 21, 2019
3,007
You do not use a diode, instead you use a resistor to limit the DC charging current of the capacitor.
The time depends on the values of the resistor and capacitor, assuming that the power supply voltage does not change.