Wire guidance - An autonomus vehicle
John Bond
Posts: 369
Hi Guys
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These summer holidays, I started trying to detect a frequency (or two) on a wire to see·how wire guidance vehicles work. I discovered how little I know about the transfer of a frequency between two wires.
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I googled the topic too and came up with little help...
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How do you make a simple wire guidance circuit? Does anyone know a good simple website on the subject?
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Summer Holidays at Christmas? Because we live on the bottom of the world, our summer holidays occur from Christmas into the New Year...
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Kind regards from South Africa
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John Bond
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·
These summer holidays, I started trying to detect a frequency (or two) on a wire to see·how wire guidance vehicles work. I discovered how little I know about the transfer of a frequency between two wires.
·
I googled the topic too and came up with little help...
·
How do you make a simple wire guidance circuit? Does anyone know a good simple website on the subject?
·
Summer Holidays at Christmas? Because we live on the bottom of the world, our summer holidays occur from Christmas into the New Year...
·
Kind regards from South Africa
·
John Bond
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Comments
Two general concepts are involved. At lower frequencies ( say normal audio up to 20KHz ) think of the wire loop as one coil of a transformer. If the receiver is a second coil, the signal in the first coil will be coupled to the second when they're close to each other. In earlier days, I ran a loop of about four turns of wire around the outside of several rooms in the house. Using a small transformer as the input to a portable audio amp, I could pickup whatever audio was put onto the outer loop as I moved around.
At higher frequencies and up into the RF area, the wire to be followed acts more like a radio antenna, so your detector has to be tuned to the expected frequency. One method is to have the pathway wire emit a steady frequency. The detector has two oscillators which change frequency due to interference between the guide wire and the two onboard oscillators. Depending on how things change, the vehicle circuitry figures out how to correct the wandering. A good analogy is to visualize two photcells straddling a white line. If the two cells are equally illuminated their outputs are equal. If one sees more light than the other, the vehicle corrects to bring them back to equal illumination.
Some of the coal mines in this area use a similar system for underground communication. Its basically a low freq radio signal on an extremely long antenna. Normal RF signal propagation through the earth is quite poor, but the low frequencies used in this system work well.
There are a few radio amateurs on the forum who may be able to assist with some expermental circuits.
Cheers......and stay out of the sun!
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Tom Sisk
http://www.siskconsult.com
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Tuned circuits sound like the answer. I've some experience with PLLs
... and your comments on the sun are really appropriate. the forcast for today is "Very Dangerous". Every one is on the beach though. The local hospital will see a lot of cases of sunburn tonight. Yes, the black people get sun burnt too. Those of us with less skin pigment have learned to use the "Austrailian rules", Slip on a shirt, Slap on a hat, Slop on sun block. I am told the UV exposure here is about 20% worse than Texas but hey, this is Africa, more people die from mosquitos.
John Bond
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Post Edited (John Bond) : 1/6/2007 2:03:24 PM GMT