Hello... This is my first post in this forum.
I am planning to power many (perhaps 16?) leds rated at 2.2volts 24ma.
However, I ran into trouble trying to use my two 2.6v 60 farad supercapacitors.
I believe supercapacitors' voltage drops quickly...
How can I use them to power my leds until the caps have no juice left?

 

Hello... This is my first post in this forum.
I am planning to power many (perhaps 16?) leds rated at 2.2volts 24ma.
However, I ran into trouble trying to use my two 2.6v 60 farad supercapacitors.
I believe supercapacitors' voltage drops quickly...
How can I use them to power my leds until the caps have no juice left?

How about you showing us what you are doing by providing a circuit? All our crystal balls are in use by the Midtown Bowling League.

 

I don't have an exact plan yet and the idea is quite simple. Do you really need a circuit?

 

This wont work well at all. Assuming you charge those capacitors to the max rated voltage, which isn't generally recommended, you have .4 volts of "drop" before the LED's stop conducting.

I can't do the math for how much current you can get from 60(?!) farads and .4 volts, but I don't imagine it's much.

You can make a "joule thief" circuit, but there are better uses of your time. Like batteries...

 

Well, if I connected the caps in series, I would be able to get 5.2volts 30farads. If I used the right value of the resistor, then wouldn't it work? The part I'm concerned about is when it falls below the 5volts. Wouldn't the leds be underpowered?

 

Have you considered a joule thief?

 

Can a joule thief put out a consistent voltage regardless of the input voltage?

 

Pretty much, that is the point of a joule thief. It puts out constant current until the battery (or supercap) is sucked dry. (LEDs like constant current.)

 

Thanks for the replies...
So here is a n00by question... Will the output voltage of the joule thief be the same if I put in something like 0.5v to 2. 5v? Will I we require a resistor for the leds?

 

No, the output voltage won't be the same, the current will. The joule thief is a current generator, and LEDs like constant current.

 

Hmm... So if I make the output voltage of the joule thief, say 5volts, can I safely hook it up to an led?

 

Hmm.. So let's say the output voltage of my thief is 4 volts. Can I safely connect it to the led?

 

Oops, thought that reply wasn't posted...

 

You want to avoid putting resistors in series to reduce the voltage because that would be wasting energy as heat.

 

Let me re-phrase the question.

If I use a joule thief to generate the proper amount of current and voltage for my LED, do I need to put a resistor in series with the proper current to make it something else?

No.