Think Create | Deqing Sun

Solar torch business card

by on Oct.25, 2010, under My gadgets



This is a business card. But in additional to its original function, it has more usage. There is a touch imbedded in the center of the image. When you touch the double E sign, the led will shine. The battery stores the energy from the solar panel. So it never requires the battery replacement.


The circuit is quite similar to a solar touch. A 4.5V amorphous silicon based solar panel charges the 3.7V Li-Ion battery through a 0.7V drop diode. But I use a touch switch instead of a regular switch. The finger is a weak conductor so I use two transistors to form a Darlington. The high gain of the circuit will supply enough current to light the led with a few micro-ampere through the finger tip.


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