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Friday, February 10, 2012

A flashlight immortal - Using super-capacitors or supercap, goldcap, supercapacitor, ultracap

The creative family

Monday, December 26, 2011

A flashlight immortal

This is a moment I want to experience the super-capacitors (or supercap, goldcap, supercapacitor, ultracap ...). These are capacitors that have huge storage capacities compared to what we did before (above the Farad, there are some that go up to 3000 farads at 2.7 volts).
So I went on Ebay and I bought a batch of 10 capacitors in Farads 2.7 volts. If we did a little calculation, a capacitor such as this one can store:

E = 1/2 * C * V ² is ½ * 10 * 2.7 ² è 36 Joules is 1 Watt for 36 seconds

In comparison, a "stack" can provide a rechargeable watt for 7300 seconds (for an AA 1700mAh) is 200 times more. However, the battery is twice as big and four times heavier. So there is a coefficient of volume equal to 100 and 50 to equal mass.

But when the capacitors have the same benefits:
  • They can load and unload quickly
  • They last much longer life (500 cycles max for a battery against over 100,000 for a capacitor)
  • They have a much better performance
The first mount I wanted done with a supercapacitor is an LED flashlight. But the big disadvantage of capacitors is that their voltage drops along their dependents. A white LED consumes very little power but needs a minimum voltage of 2 volts to light. A capacitor which has a maximum voltage of 2.7 volts would be helpful if on the beach 2V / V 2.7 is on 25% load.
So I searched for a solution to my problem on the internet and I found a very interesting circuit: the "Joule Thief" (in French: Joule Thief). Most times, it is used to light a LED with a AA battery until the last joule (or almost).

Here is a diagram of a joule thief:

This is actually a self-oscillating circuit or LED serves as a "diode" in the second coil. No matter what the voltage across the battery, there will always be a sufficient voltage across the LED.
By replacing the battery with the supercapacitor, I thought that it should work. And yes, it works!
So I have a flashlight that illuminates for 15 minutes (without loss of brightness) and that loads in ... 10 seconds.
Components to achieve it are:
  • A white LED (retrieved on a flashlight whose battery was empty)
  • A super capacitor (10F, 2.7 V)
  • A transistor
  • A torus
  • 1 k ohms resistance
  • The wire
  • A breadboard


Original Article at...

Pretty Cool and Simple Setup. I might just have to try building one of these:)


A flashlight immortal - Using super-capacitors or supercap, goldcap, supercapacitor, ultracap
Supercap lights your way in times of need - Hack a Day
Google Translate
joulethief2.jpg (JPEG Image, 720 × 450 pixels)
La famille créative: Une lampe de poche immortelle
Joule thief LED driver - Hack a Day
TE Index for website
Make a Joule thief.
joulethief1.jpg (JPEG Image, 500 × 293 pixels)

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