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Electronics => Projects, Designs, and Technical Stuff => Topic started by: Didix on February 17, 2015, 07:35:45 pm

Title: Driving a white LED with a single Gold Cap 2.7V 22F
Post by: Didix on February 17, 2015, 07:35:45 pm

Any ideas how I could do this?

-Didix

Title: Re: Driving a white LED with a single Gold Cap 2.7V 22F
Post by: Mr. OBrien on February 17, 2015, 07:46:42 pm

A quick google and I believe this circuit will do what you need with very little tweaking. http://cappels.org/dproj/ledpage/leddrv.htm (http://cappels.org/dproj/ledpage/leddrv.htm)

Title: Re: Driving a white LED with a single Gold Cap 2.7V 22F
Post by: Phaedrus on February 17, 2015, 07:50:38 pm

What context is this in? Is this cap being used to keep some kind of indicator light on after the supply voltage has been removed? Is there a reason you're using this specific cap? What's the Vfd and If of your LED? What level of brightness do you need? What kind of battery cap life are you aiming for?

If you just need to boost voltage to power some LEDs from a low voltage source, something like a Joule Thief would work, or even that "free energy" circuit Dave debunked a while back: http://i.imgur.com/eD3iO9V.png (http://i.imgur.com/eD3iO9V.png)

Title: Re: Driving a white LED with a single Gold Cap 2.7V 22F
Post by: Didix on February 17, 2015, 08:00:25 pm

Well, I never have used a Gold Cap before and I just wanted to have one  8)

Now I am looking for some test applications.

I have a flashlight with a white LED and a Gold Cap. The Gold Cap is charged by shaking the lamp (a neodym magnet and a coil that act as a generator).
That was acually inspiring me for my first trial.

I will follow up on your hints! Thanx a lot  :-+

-Didix

Title: Re: Driving a white LED with a single Gold Cap 2.7V 22F
Post by: compet17 on February 22, 2015, 11:50:55 am

Just Google for "joule thief". You will find many simple schematics. And if it works with a 1.5Vbattery, it will also work with a 2.5V cap. Some of the circuits go down to a supply voltage of 0.5V

Title: Re: Driving a white LED with a single Gold Cap 2.7V 22F
Post by: mariush on February 22, 2015, 12:33:07 pm

Buy a proper boost led driver, that will work on a wide range of input voltages.

For example this one will work from 0.8v to 8v so it would pull out a lot of energy from the capacitor before crapping out : http://uk.farnell.com/diodes-inc/zxsc310e5/ic-led-driver-boost-converter/dp/1226478 (http://uk.farnell.com/diodes-inc/zxsc310e5/ic-led-driver-boost-converter/dp/1226478)
It would also allow you to control the amount of current going into the led, so you could add for example a "feature" like low / med / high brightness slider.

See page 8 of datasheet, only need an inductor and a transistor and a resistor (to control current) to make it work.

Title: Re: Driving a white LED with a single Gold Cap 2.7V 22F
Post by: Didix on February 22, 2015, 07:07:49 pm

I am already collecting toroid cores  :)

-Didix