jws@cica4.mlb.semi.harris.com (James W. Swonger) (03/22/91)
Ultrasonic FM?
dale@lamont.ldgo.columbia.edu (dale chayes) (03/23/91)
In article <430.27e07fdb@brb.isnet.inmos.co.uk>, robw@brb.isnet.inmos.co.uk writes: > I need to transmit some data between two systems about 10 feet apart > without being physically connected. > They will not always be line-of-sight, and they may be UNDERWATER ! Well, your' in luck. The January 91 issue of the IEEE journal of Oceanic Engineering was a special issue on ocean acoustic data telemetry (Volume 16, Number 1 ISSN 0364-9059) As with all telemetry system designs, one of the first questions you have to answer is; how much data, how often. IE: what throughput do you need to get the job done? Have fun, Dale -- Dale Chayes Lamont-Doherty Geological Observatory of Columbia University Route 9W, Palisades, N.Y. 10964 dale@lamont.ldgo.columbia.edu voice: (914) 359-2900 extension 434 fax: (914) 359-6817
bender@oobleck.Eng.Sun.COM (I want to be eating rich soup in another town) (03/23/91)
In article <430.27e07fdb@brb.isnet.inmos.co.uk> robw@brb.isnet.inmos.co.uk writes:
->I need to transmit some data between two systems about 10 feet apart
->without being physically connected.
->They will not always be line-of-sight, and they may be UNDERWATER !
How about something like sonar, i.e. use sound? I don't know what the
propagation delay would be, and what kind of data rates you would get. Or
how about low-power FM? Or, magnetic induction - you should be able to get
10 feet or so out of a system like that.
mike
--
Won't look like rain, Won't look like snow, | DOD #000007
Won't look like fog, That's all we know! | AMA #511250
We just can't tell you anymore, We've never made oobleck before! | MSC #298726whit@milton.u.washington.edu (John Whitmore) (03/23/91)
In article <430.27e07fdb@brb.isnet.inmos.co.uk> robw@brb.isnet.inmos.co.uk writes: >I need to transmit some data between two systems about 10 feet apart >without being physically connected. >They will not always be line-of-sight, and they may be UNDERWATER ! >Any suggestions ? Well, electric current is out (no wires) and light might not travel well if one is above water and the other below. Sound seems like your best bet (ground conduction will ALWAYS work, won't it?). Think in terms of a 110 baud modem (and you'll want some resonant gizmo to couple the sound to the ground; a tuned dashpot should do). Seismologists routinely pick up unintended noises (traffic, wind blowing the trees, etc), so a narrow-band ground-vibration gizmo should be able to be sensed at far more than 10 feet. You don't say if the water is salt or not; if it's fresh, the little 49 MHz remote-control circuits should be able to punch through a ten foot separation. If it's salt, you'll need to ask someone more knowledgable than I about the attenuation versus frequency. John Whitmore
don@zl2tnm.gp.co.nz (Don Stokes) (03/23/91)
robw@brb.isnet.inmos.co.uk writes: > I need to transmit some data between two systems about 10 feet apart > without being physically connected. > They will not always be line-of-sight, and they may be UNDERWATER ! > > Any suggestions ? How about an acoustic coupler? Make it a bit more sensitive than the norm, and perhaps a bit louder, and error correct to the max. It may not be too hot on dry land but should work wonders underwater. Don't expect terribly high throughput though -- with the vaguaries of the media, I'd expect you'd be stuck with FSK. Failing that, I think you're looking at a low powered radio link, water may be a problem in that respect (I haven't actually tried taking my HT swimming with me 8-). Don Stokes, ZL2TNM / / don@zl2tnm.gp.co.nz (home) Systems Programmer /GP/ GP PRINT LIMITED Wellington, don@gp.co.nz (work) __________________/ / ---------------- New_Zealand__________________________
dale@lamont.ldgo.columbia.edu (dale chayes) (03/24/91)
>>> In article <430.27e07fdb@brb.isnet.inmos.co.uk> robw@brb.isnet.inmos.co.uk >>asked for suggestions about telemetry (persumably of data) over 10 feet, >>perhaps, or sometimes underwater. >> >> In article <18928@milton.u.washington.edu>, whit@milton.u.washington.edu >(John Whitmore) observed (in my words) that wires were out, and light might >pose problems of alignment, so he suggested a tuned dashpot and 110 baud data >rates, or if in fresh water, how about 49 megs (presumably RF) remote control >systems. > Its not impossible to get above 110 baud, but its not easy. See the articles in the Ocean Engineering issue I mentioned the other day. Small, high frequency (on the order of 50 to 300 kiloHertz) transducers are easy to come by (they are used in fish finders, ultra sound imaging, and depth sounders for small boats.) You don't have to do much to protect the cables/electronics in 10' of water. National makes an ultrasound transceiver (IC) designed for acoustic operation in this range. Its an LM1812, and the specs and application discussion are in Volume 3 of the National Linear databook. Included in their "typical applications" are sources for transducers. (Standard Disclaimer....) -- Dale Chayes Lamont-Doherty Geological Observatory of Columbia University Route 9W, Palisades, N.Y. 10964 dale@lamont.ldgo.columbia.edu voice: (914) 359-2900 extension 434 fax: (914) 359-6817
onymouse@netcom.COM (John Debert) (03/24/91)
From article <10286@exodus.Eng.Sun.COM>, by bender@oobleck.Eng.Sun.COM (I want to be eating rich soup in another town): > In article <430.27e07fdb@brb.isnet.inmos.co.uk> robw@brb.isnet.inmos.co.uk writes: > ->I need to transmit some data between two systems about 10 feet apart > ->without being physically connected. > ->They will not always be line-of-sight, and they may be UNDERWATER ! > > How about something like sonar, i.e. use sound? I don't know what the > propagation delay would be, and what kind of data rates you would get. Or > how about low-power FM? Or, magnetic induction - you should be able to get Will any part of them always be in water? if so, how much? What is meant by "not always be line-of-sight?" The answers to the above will determine what method of communication would best. -- jd onymouse@netcom.COM
ssave@ole.UUCP (Shailendra Save) (03/25/91)
From article <430.27e07fdb@brb.isnet.inmos.co.uk>, by robw@brb.isnet.inmos.co.uk: > I need to transmit some data between two systems about 10 feet apart > without being physically connected. > They will not always be line-of-sight, and they may be UNDERWATER ! Try A.M., sound travels nicely under water.
will@rins.ryukoku.ac.jp (will) (03/25/91)
I read a few years back that DoD was working in this area and found
GREEN LASER light to be very effective for sub to sub communication.
Sorry, that's all I know about it, just read it in some mag. Years
ago.
William Dee Rieken
Researcher, Computer Visualization
Faculty of Science and Technology
Ryukoku University
Seta, Otsu 520-21,
Japan
Tel: 0775-43-7418(direct)
Fax: 0775-43-7749
will@rins.ryukoku.ac.jpsiegman@sierra.STANFORD.EDU (Anthony E. Siegman) (03/27/91)
For low enough data rates and enough scattering objects around you might be able to do it optically, i.e. with modulated LEDs or laser diodes and photodetectors. I believe there are wireless LANs for use in offices in which the IR transmitters just spray light at the ceiling and let it scatter to receivers randomly located around the room. Might also do a bistatic version, i. e. simplified low-power units at the two sources, a more sensitive and powerful receive-and-retransmit relay unit in between. --AES