Q : HF powered circuit ?

[JCR]

Hi all,

I'm thinking to supply a low-power circuit (say 300 mW)
without wire nor battery. I suppose it is possible to
use a HF emitter with a directionnal beam, to send
electromagnetic waves to a receiver that will just
detect and correct the HF to DC.

Am I dreaming or is reasonable idea ?

TIA

 

[Andrew Paule]

Reasonable - many companies have done this

 

[Ian Stirling]

Hi all,

I'm thinking to supply a low-power circuit (say 300 mW)
without wire nor battery. I suppose it is possible to
use a HF emitter with a directionnal beam, to send
electromagnetic waves to a receiver that will just
detect and correct the HF to DC.

Am I dreaming or is reasonable idea ?

It may or may not be reasonable, and may be hard to do witbout interfering
with othre stuff.
How far?
1mm is almost trivial, 10cm harder, and 10m gets interesting.
How large/whjat is the object, will it move, ...

 

[Tim Shoppa]

Hi all,

I'm thinking to supply a low-power circuit (say 300 mW)
without wire nor battery. I suppose it is possible to
use a HF emitter with a directionnal beam, to send
electromagnetic waves to a receiver that will just
detect and correct the HF to DC.

Am I dreaming or is reasonable idea ?

Define "HF" and "directional beam".

Transformer coupling power to avoid electrical contacts is done all
the time. There are at least a couple brands of rechargable electric
toothbrushes which charge up this way. This isn't usually HF, usually
it's 60Hz, though scaling this up to the low MHz ought to just work.

Now, what you're talking about with "HF" and "directional beam" makes
me think "under 30MHz" (traditional upper frequency of HF band)
and "Yagi" (a well-known directional antenna). That would imply that to get any
sort of efficiency, at least one of the antennas is dimensionally larger
than 10 or 20 feet. Am I thinking of the same thing that you're thinking?

Even then I'd be surprised if you got efficiencies more than a couple of
percent.

Now, change "HF" to "microwaves" and then we're talking action. (And cooking!)

Tim.

 

[Paul Burridge]

It may or may not be reasonable, and may be hard to do witbout interfering
with othre stuff.
How far?
1mm is almost trivial, 10cm harder, and 10m gets interesting.

ISTR Nick Tesla accomplished the wireless transmission of power over
25 miles or so way back in the 1930s!

 

[James Meyer]

The aim is : someone is on a scene making a public performance,
and wearing sensors connected to an embedded emitter circuit,
that will transmit those informations back to a local station
for processing. I don't want to use wires as the performer
should evolve freely, and it is not easy to find weightless
batteries that will work for hours. So I thougt to "send" electric
power wireless. In that case, energy loss should not really be
a problem, within acceptable limits. The distance between
the performer and the receiving station is roughly 10 meters.

Any suggestions ?

Yes! Stop thinking about this project. As others have pointed out, it
is impossible to send energy without having some of it "spill over" and not be
consumed where you want it. In short, you will probably cook the performer to
death before you get enough energy into your device to do any good.

Of course, I have seen several performers who would be better off cooked
to death.

Jim

 

[Tim Shoppa]

Yes! Stop thinking about this project. As others have pointed out, it
is impossible to send energy without having some of it "spill over" and not be
consumed where you want it. In short, you will probably cook the performer to
death before you get enough energy into your device to do any good.

Of course, I have seen several performers who would be better off cooked
to death.

There was a very short Arthur C Clarke story where the audience used their
reflective programs in an outdoor soccer stadium to do exactly that to a
dishonest referee...

Tim.

 

[Jim Meyer]

[email protected] (Tim Shoppa) wrote in message

There was a very short Arthur C Clarke story where the audience used their
reflective programs in an outdoor soccer stadium to do exactly that to a
dishonest referee...

Tim.

That was one of his that stuck in my mind. Hell, *all* of his
stories stuck in my mind!

I always wondered how each audience member got enough feedback to
be able to place their little spot of reflected sunlight right on the
ref along with all the other little spots. Then I found out about the
survival signaling mirror that downed WWII pilots used to catch the
attention of search planes. Ducedly clever, that.

Rather than spoil it, I'll let the audience try to come up with
the method used.

Jim