LED flashlight based on a white LED

Posted on Feb 7, 2014

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

LED flashlight based on a white LED
Click here to download the full size of the above Circuit.

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. 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. 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. 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 10 µH and 68 µH 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. 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.

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