Re: life span durable ground based 'satellite' device.

I remember building a crystal radio once as a kid, and how it was able to
power a small earphone with no battery or apparent power source. The power
transmitted by the station powers the radio. Considering the small amount of
energy you'd need, it seems like you could adapt this principle. It does fit
your main criteria of a nearly indefinite power source. I don't expect AM
radio to be going away anytime soon. Of course this was also the principle
behind Nikola Tesla's Magnifying Transmitter (
http://en.wikipedia.org/wiki/Magnifying_Transmitter )

You only need 5 Watts for 5 Seconds (25 wattseconds) once a day. So the
other 86,395 seconds of the day this thing is just sitting there. It seems
if it could be drawing just a trickle ( approx 300 microwatts continuously)
from somewhere you could get your 25 wattseconds of energy for the next days
readings.

Perhaps some of the folks in the radio newsgroups could give a quick thumbs
up/down on the concept, as I don't know how much receive power would be
typical off the AM band.

Also, you didn't mention it, but you will have a small constant current draw
from the real time clock which will be needed to tell the microcontroller
when to come out of sleep mode.

Chris


<alphacentauri@xxxxxxxxxxxx> wrote in message
news:1160599507.495390.276260@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Christopher Ott wrote:
Not wanting to sound like a "Free Energy" kook,

Don't worry, I'll be the kook here. ;-D

but you might want to look
into how much receive power you could siphon from local AM radio
stations.
From the numbers you've provided, I came up with you needing less than
300
microwatts continuous (obviously you'd need some charge/collection
circuitry). How big an antenna can you tolerate?

Huh? Is this for real? If so, "Free Energy" indeed.
Like that Lucille Ball story?
http://www.healthyhearing.com/library/ate_content.asp?question_id=102

Do you have some more specific information about the workings of this
idea?

A big antenna wouldn't be a problem.



.

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