Capacitor charging project

[Johnny Ohm]

My project is pretty simple: I have a capacitor (size and type is not important) connected to a battery. Im hoping to be able to check the charge of the capacitor without discharging it. Is there a way to simple check the charge? If not is there a way to simply indicate when the capacitor is fully charged?

 

[Boncuk]

Capacitor charging

Hi Johnny Ohm,

it is better to limit the charge current with a low value resistor. An uncharged capacitor acts like a momentary short circuit when being charged.

If you always charge to the the same voltage, a comparator circuit might be applied to indicate full charge. For different charging voltages it requires more circuitry such as switches and precise voltage dividers.

Boncuk

 

[Analog]

My project is pretty simple: I have a capacitor (size and type is not important) connected to a battery. Im hoping to be able to check the charge of the capacitor without discharging it. Is there a way to simple check the charge? If not is there a way to simply indicate when the capacitor is fully charged?

When a capacitor is hooked to a voltage source, like a battery, it will charge up to the voltage of the battery. If it is a decent cap, then you can remove it from the battery and it will hold the voltage for a time, perhaps a long time if it is not leaky. To check, use a decent voltmeter. They generally have a high enough input impedance to not quickly discharge the cap, depending upon how big the cap is. You did not say what the size of the cap or voltage of the battery are.

 

[Boncuk]

You did not say what the size of the cap or voltage of the battery are.

... the OP obviously wants to charge any capacitor. (Size and type are of no importance)

Boncuk

 

[Johnny Ohm]

Thanks for the replies,

Here is a little more info on my project. I have a flashlight which is powered by a super capacitor (like the "faraday flashlight"). I want to be able to check the charge of the capacitor and indicate that charge with a LED or some indicator. I like the idea of checking the charge with a multimeter, but in this sutuation a multimeter would not always be on hand.

The makeup of the capacitor isnt important, Im just using the super capacitor in the flashlight as an example.

How would a basic comparator circuit look for this application?

Thanks,
JΩ

 

[OutToLunch]

wouldn't the brightness of the light be an indicator of remaining charge? or is this a constant current led light? this might be interesting to you...

**broken link removed**

 

[scaifie]

You could perform A/D conversions on the voltages and perform a comparison and display it however you want but I wouldn't say its the best way of doing it. The power drawn would be very small.