www.jens-seiler.de The JarLight Mark 3 www.jens-seiler.de

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JarLight Mark 3winking smiley LED flashlight (white)

the JarLight

The "JarLight" is a small flashlight based on a white light emitting diode (LED). It is powered by a single battery cell. This combination enables a very compact case at a very high light power and long-life. Not only of the battery but also of the LED.
To generate a voltage of 4 volts out of a single 1.2 volt cell it is necessary to make use of a little circuit, based on the LT1073-5 IC, a coil, a diode and a capacitor. It's easy to build and you find the circuit further down.

Comparison to a Maglite Solitaire

To compare the features I used a MagLite Solitaire because this flashlight is comparable in size and power (one cell only). The photographs show the light-cones of the two flashlights as seen from the side and as a reflection of the circle on a white sheet of paper.

Two features are noticeable:

  • The colour temperature of the white LED is much higher than that of the Maglite. The light appears to be much whiter and more natural.
  • The intensity of the JarLight is much higher as well

Beside the light-power the battery-usage is interesting too. I have charged one and the same 750mAh micro-accumulator cell (size AAA) with a microprocessor controlled battery charger and used it for the test.

The results:

JarLight Mark 3winking smiley:5 hours
MagLite Solitaire:3.5 hours

comparison of the light cone circles

The circuit and the JarLight Mark 3

Above you see the circuit schematics of the JarLight. The LT1073-5 IC is being produced by Linear Technology. You can find a verbose datasheet on their pages too out of which I derived the circuit above. The coil with 82 micro Henry can of course be substituted by a serial combination of two smaller coils. I use two inductivities of 10µH and 68µH successfully.
According to the datasheet of the diode must be a very fast one. So the 1N5818 Schottky-diode is recommended. The capacitor is not necessary for using the circuit above as a LED driver but it produces a nice after-glow when switching off the current.
The LED I used is a 5mm white LED with a rating of 5.6 Cd and an opening angle of 20°.

the inner life of the JarLight

On the right side you see the inner "life" of the JarLight. IC, inductivities, diode and capacitor find their place on a small circuit board. The inductivities are "cloaked" in resistance-casing right.

The small white box is a plug that can be used to recharge the 750mAh accu cell without opening the casing.

The Jarlight from aboveThe JarLight seen from the side

And if you got some questions left you can ask them in my forum. I will try to answer them!

Here you can find the follow-up models of the Mark 3. The site is written in german but the pictures are speaking for themselves ;-)

To the experimental corner-Forum


© Jens Seiler, last change: 10/06/2003