Subject pretty much says it all........is it possible to light an LED (continuously, or pulsed) from an antenna ONLY (only power source, that is)? Does anyone know of any schematics for building such a circuit?
Patrick Leonard wrote: You need to look up Nikola Tesla, that was his gig around the turn of the (20th) century.
DLC
: Subject pretty much says it all........is it possible to light an LED : (continuously, or pulsed) from an antenna ONLY (only power source, that is)? : Does anyone know of any schematics for building such a circuit?
-- ============================================================================ * Dennis Clark dlc@frii.com www.techtoystoday.com * * "Building Robot Drive Trains" published by McGraw-Hill 2002 * ============================================================================
I'm familiar with the work of Tesla; no this question was not an attempt at any kind of free energy extraction.
I'm just curious if radio stati> You need to look up Nikola Tesla, that was his gig around the turn of the
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I DO know Tesla's work quite well, and I realise my reply was misleading. I didn't mean to imply Tesla was a free energy kook, rather, I wanted to make it clear that *I* was not a free energy kook misinterpereting his work. I apologise if this was unclear.
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Well, this is what I have been experimenting with using a plasma ball (see my other post regarding antennas). But trying to hook up the LED across the antenna doesn't seem to do the trick. Rather, it only works when I wire the antenna, LED, and a ground in series (and it doesn't even have to be a good ground)
I asked pretty much the same question a couple of years ago, and was pointed to web sites dedicated to "crystal radio" which basically powers the high impedance headphone rather than the LED (+demodulates AM, but that you don't care about). I was also pointed to the web site of someone living under high voltage power lines who could light a light bulb just by induction (with the proper loop antenna of course).
Unless you have dedicated circuitry for transmitting energy via RF (two coil/loop antenna setup), the energy output of an antenna will most probably not be enough for anything useful (I even tried to power one of the low power microcontrollers from an antenna+rectifier bridge). An example of such setup is the SAW based RF tags.
Jean-Michel
In article , snipped-for-privacy@rogers.com mentioned...
Yeah, you just bend the LED leads in the shape of a dipole antenna.
Somewhere I read about using just such a device to find out if your microwave oven is leaking microwaves around the door. You just dim the room lights, and put a cup of water in the microwave and turn it on high. Then hold the LED with its legs bent like an antenna next to the door edges, and see if it lights up.
If it does, then you got a problem!
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In article , snipped-for-privacy@rogers.com mentioned...
Your average local radio station has millivolts of signal strength, but that can be stepped up to a higher voltage, with a coil. If you're close to a high power radio transmitter, then it's possible to light up things like neon lights, etc. One guy claimed that the electric lights in his chicken coops lit up from the local radio station transmitter, so he could get the chickens to lay more eggs. Don't remember why, tho.
I've used a red LED connected to a coil of a few turns of 24 gauge wire to sense RF when I'm playing.. erm, experimenting (yeah, that's the word) with transmitters. But a 1.5V, 25 mA submini bulb from Radio Scrap works very well, too.
You can get on Gollum's website of crystal radios and see the schematics of some of the self-powered xtal radios he's built. Basically they rectify the RF from the antenna and use it to power 1 or 2 transistors to amplify the AF signal. This could be enough to light up a LED. I've run as little as a few tens of microamps or less thru a blue or white LED and it's clearly visible, which makes you think about how amazingly sensitive the eye really is. You go outside and look at the stars, and you see some tiny speck in the sky twinkling. How much is the power of that starlight hitting your retina? Nanowatts? Picowatts? Femtowatts? Whatever.. See here for the next lower prefix for the above.
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Done that half a kilometer from a major AM transmitter site. String out (as in outdoors) a long wire (several meters but less than 1/4 wavelength), and put an inductor from one end to ground that makes this resonate. Halfwave rectify (with respect to ground) where the antenna meets the inductor. Maybe you get adequate voltage at around a milliamp to optimistically possibly a few milliamps, enough for better modern blue, white, or InGaN green LEDs to be used as a dimmer sort of nightlight. You can illuminate a room well enough from this to navigate through if dark-adapted.
CAUTION: 1: the current through the diode (and maybe through the LED) may have enough harmonic content to possibly result in rebroadcasting the nearby AM station at harmonic frequencies to an extent that you may not be allowed to do. 2: Particularly large/nearby/efficient powersucking antennas may measurably decrease reception somewhere else or may measurably affect the impedance of the transmission antenna or may measurably detune it, which may possibly cause yourself trouble. 3: What will you do about lightning? A near-miss may send pieces of your LED all over the place. A direct hit can do worse.
- Don Klipstein ( snipped-for-privacy@misty.com)
Oh Dear! I've one of those cell-phone cradles with a black-blob flasher circuit that goes off when the phone rings - it flashes if stood on top of the operating microwave (on the steel case). Thinking even thin steel would stop any harmful radiation, I've put this down to some less nasty form from the transformer...
Tsk-tsk..
I scrounged a magnetron from a defunct microwave oven at work, and put it in my desk. I decided that it needed more exposure, so I took it along on one of my sojourns to another campus. I showed it to some people and they said, what's that? I said it's a magnetron. They said, so, what's a magnetron? Well, I said, this is what makes the microwaves in your microwave oven. Oh, they say, and look at it a bit more closely. But most people haven't a clue as to what is inside their microwave oven, other than the plate that spins around.
-- @@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@ ###Got a Question about ELECTRONICS? Check HERE First:### http://users.pandora.be/educypedia/electronics/databank.htm My email address is whitelisted. *All* email sent to it goes directly to the trash unless you add NOSPAM in the Subject: line with other stuff. alondra101 hotmail.com Don't be ripped off by the big book dealers. Go to the URL that will give you a choice and save you money(up to half). http://www.everybookstore.com You'll be glad you did! Just when you thought you had all this figured out, the gov't changed it: http://physics.nist.gov/cuu/Units/binary.html@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@
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