From: John De Armond
Subject: Re: OT. A self powered Radio, Do anyone remember Popular Science
Date: Sun, 23 Dec 2007 13:54:27 -0500
On Sun, 23 Dec 2007 07:21:07 -0800 (PST), Jack <email@example.com> wrote:
>Thanks fellows for the imput. Not being a wizard I had no idea if it
>was plausible or not.
To put this in further perspective, your common everyday ionization smoke detector is
a beta battery (actually it uses alpha particles but the name still sticks). About
1uCi of Am241 is deposited inside a chamber that is open to air. Am241 is a powerful
alpha emitter. Alphas are positively charged. An electrode is located near the
source to collect the alphas. This collection of charge causes a current to flow in
the external circuit. Combustion products that enter the chamber attach to and
neutralize alphas and the ions they form. This reduces the ion current. The
electronics detect this and sound the alarm.
The magnitude of the current is something on the order of 1E-12 amps. Current so
small that even a printed circuit board is too lossy. If you look inside a smoke
detector, you'll find that the electrode touches practically nothing except the input
pin of the detector IC. The pin is typically bent up off the board and spot-welded
to the electrode. Even a fingerprint that contacts the electrode will completely
swamp the tiny ionization signal.
One is simply NOT going to power a radio with that magnitude of current.
>Now I wonder why Popular Science bothered to print the article.
PopSci? The best fictional science fit to print. I've read that rag for almost 50
years, off and on, and the one conclusion I can draw is that if it appears in
PopSci(fiction) then the odds of it being real are very slim indeed.