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10cm electromagnetic RS232 link.

I'm looking for a 10 - 30 cm electromagnetic link which I can use to
transmit serial RS232 data in simplex mode.

Ideally, there would be a receiver which would sence the presence of the
transmitter. The receiver would modify the EM field of the transmitter(
like a transformer) for it's communication. This would give the ultimate
low power solution for the receiver side.

Does any such animal exist?
 
B

Ben Pope

Jan 1, 1970
0
I'm looking for a 10 - 30 cm electromagnetic link which I can use to
transmit serial RS232 data in simplex mode.

Ideally, there would be a receiver which would sence the presence of the
transmitter. The receiver would modify the EM field of the transmitter(
like a transformer) for it's communication. This would give the ultimate
low power solution for the receiver side.

Does any such animal exist?

Whats wrong with IrDA? Too directional?

Ben
 
P

Paul Hovnanian P.E.

Jan 1, 1970
0
I'm looking for a 10 - 30 cm electromagnetic link which I can use to
transmit serial RS232 data in simplex mode.

Ideally, there would be a receiver which would sence the presence of the
transmitter. The receiver would modify the EM field of the transmitter(
like a transformer) for it's communication. This would give the ultimate
low power solution for the receiver side.

Does any such animal exist?

Bluetooth.
 
A

Active8

Jan 1, 1970
0
you don't mention speed or regulatory body. if you can deal with not so
fast, 13.5MHz/140kHz RFID meets your EM field wish and maybe range.

the last hard range data i've seen for RFID is 10cm or so with a Rx pre-
amp. check RFID links at Atmel and Microchip and maybe national -
whatever google returns. from what i can glean from your post, this is
what you want.

but don't overlook IrDA as Ben said. IrDA would be the simplest, by far.
if you need more speed maybe Bluetooth, as Paul said, will work, but i
have a feeling bluetooth would be overkill.

and don't forget, if you don't brush, you'll have notooth :-0

HTH,
mike
 
A

Active8

Jan 1, 1970
0
Whats wrong with IrDA? Too directional?
hey ben. thanks for bringing it up. i've googled it, but haven't come up
with much well organized info re:

IR range in daylight, night, bright sun...

can you (or anyone) fill me in? talk range, power levels, current, etc.
if possible. refs/ANs would be helpful, too, if you can recall any.

TIA & brs,
mike
 
B

Ben Pope

Jan 1, 1970
0
Active8 said:
hey ben. thanks for bringing it up. i've googled it, but haven't come up
with much well organized info re:

IR range in daylight, night, bright sun...

can you (or anyone) fill me in? talk range, power levels, current, etc.
if possible. refs/ANs would be helpful, too, if you can recall any.

TIA & brs,
mike

www.irda.org/

has links to manufacturers products IIRC.

Ben
 
R

Roger Lascelles

Jan 1, 1970
0
I think the full Irda spec is rarely worth the effort - there are so many
software layers in the spec that you typically end up buying a code library.
I get the feeling that the Irda standard has struggled due to complexity and
compatibility problems.

However, I can recommend you use the Irda *physical spec* . See the irda
website - one of the docs has a nice diagram showing how RS232 serial data
is converted to a series of LED flashes.

There are "dongles" you can buy which plug onto a PC serial port and have an
Irda transmitter/receiver on the other end. Some of these are extremely
simple - you pump serial data out of the PC and it gets converted straight
to Irda physical layer, byte for byte. Same in the other direction. All
the complicated Irda software protocol is done in software and is not needed
if you just want RS232 communication. This approach is used by some mobile
phone Irda also - the hardware standard is used, but not the full Irda
software protocol.

This won't work with USB dongles which require the full Irda software
layers.

There are inexpensive Irda pcb mount transimtter - receiver modules commonly
available which include the photo detector and electronics to convert
incoming infrared to to a nice digital signal. To transmit you put current
through the LED included in the module. For send - only you can just switch
on-off an ordinary infra red LED - the Irda docs tell you the LED wavelength
to aim for. With 80mA through a LED, I got a metre or two range indoors and
our customers use it in full sunlight at 30cm.

LED flash timing is easily handled by some assembler loops. We used a start
of message and end of message sequence to let the PC work out when a block
of data was sent. You might need a checksum too.


Roger
 
A

Active8

Jan 1, 1970
0
our customers use it in full sunlight at 30cm.
thanks for the heads up on the spec and all. what i'm after however, is
range info for a non-data app. CW or low pulse rate. i've seen TV
remotes that will bounce off a wall into the next room which is about
what i'd like for outdoors in full sunlight, but the more info i have,
the better.

the manufacturer data is either buried where google can't find it or i'm
using the wrong search string. "range" turns up info on the wavelength.
"distance" turns up manufacturing process info.

now of course, any range capability of IR diodes will be dependant not
only on the current (power), but the particular diode and additional
optics. i'm really only concerned with what the bugger can do as it is.

brs,
mike
 
P

Paul Hovnanian P.E.

Jan 1, 1970
0
I'm looking for a 10 - 30 cm electromagnetic link which I can use to
transmit serial RS232 data in simplex mode.

Ideally, there would be a receiver which would sence the presence of the
transmitter. The receiver would modify the EM field of the transmitter(
like a transformer) for it's communication. This would give the ultimate
low power solution for the receiver side.

Is your goal to have an r.f. powered transmitter?
Does any such animal exist?

I'm not sure what the power requirements of the rest of the transmitter
are, but there might be some RFID technologies that can power and read
some simple external devices and pass that data back to the receiver.
 
S

Spehro Pefhany

Jan 1, 1970
0
I'm looking for a 10 - 30 cm electromagnetic link which I can use to
transmit serial RS232 data in simplex mode.

Ideally, there would be a receiver which would sence the presence of the
transmitter. The receiver would modify the EM field of the transmitter(
like a transformer) for it's communication. This would give the ultimate
low power solution for the receiver side.

Does any such animal exist?

You can do this with wound or even printed magnetic coils that run
at relatively high current for the transmitter. That's using magnetic,
not EM, coupling, essentially an air-core transformer.

Best regards,
Spehro Pefhany
 
S

Spehro Pefhany

Jan 1, 1970
0
I'm looking for a 10 - 30 cm electromagnetic link which I can use to
transmit serial RS232 data in simplex mode.

Ideally, there would be a receiver which would sence the presence of the
transmitter. The receiver would modify the EM field of the transmitter(
like a transformer) for it's communication. This would give the ultimate
low power solution for the receiver side.

Does any such animal exist?

You can do this with wound or even printed magnetic coils that run
at relatively high current for the transmitter. That's using magnetic,
not EM, coupling, essentially an air-core transformer.

Best regards,
Spehro Pefhany
 
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