March 18, 2007

Mobile Flashers, tuned to thrill!

a mobile flashing stickerThe cellular revolution has given us a lot. It has given us the connectivity we needed so dearly. It has also fostered the development of many accessories in the process. For example, here I show you a simple mobile flashing sticker I bought in Calcutta. Just take off the oily sticker/cellophane at the back of the flasher and stick it on the mobile, you are done! The device will flash whenever the phone is in use.

You can see LEDs (smd versions) and other devices through a magnifying glass, in the embedded circuit, through the transparent top. But, where is the power source? I couldn't recognize one. May be there is. But a more plausible possibility is there isn't one. There's one coil type of thing incorporated within it, which possibly generates electricity from the Radio Frequency radiations in the Gigahertz range by induction(Lenz's law). There could be another type of energy capturing device, in the form of resonant tuned (LC/RC) circuits. The induced a.c. current could then be rectified by surface mount diodes and the resulting d.c. voltage could then be doubled or multiplied by capacitor-diode networks. This voltage amplification is necessary as there would be voltage drops (about 600mV/each silicon diode) in the LEDs and across other components too. Thus the sticker probably draws its energy from the emanating radiations (of the cell phone itself).

Reminds me of the principle of simple batteryless crystal radio receivers of the past. Cool yeah!
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