Forever Flasher
Approx construction cost US$10
A novel flashing LED that could run for over 20 years on a 9V lithium battery or "forever" using the "free energy" from a TV aerial or similar.
This article describes how a simple micropower l.e.d. flasher circuit may be pulsed off less than 1uA power at 9V. It uses just under 10uW, which, in theory, will enable this circuit to run for many years off a small 9V lithium battery. Although such a battery has a nominal shelf life of ten years, it should without trouble be able to power this circuit for twenty or thirty years or more. In some cases, even zinc carbon batteries have been known to last this long.
Another conspicuous feature of the Forever Flasher circuit is the provision for an aerial and an earth connection connected to a standard diode "pump" circuit. This is included in the circuit because, due to its miniscule power consumption, the flasher may in some cases be powered off a television aerial, in combination with a ground wire.
More details on this construction project can be found in the January 2002 issue of EPE Online, the world's first web-delivered electronics and computing hobbyist magazine.
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