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Do anyone can guess how do this work?

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elctrified

New Member
hello ,
I am willing to build a device that basically is signal transmitte-receiver system, probably a radio trasmitter -receiver, but I am open to other solutions,
Now I have viewed a lot of circuit schematic on the net but I have not found anything that work for what I need.
The prolem is that for my project I need something very selective, I think.

I have considered various options included IR and other tricky way, until I come across a new product that seem could fit with my project.
The link for that product is this
http://www.loc8tor.com/
As you see they make use of a small tag that emitt a radio signal, now the interesting part is that this signal seem to be very narrow angle, to be precisely located by the receiver...or perahps is it something else but at the end the system behave that way since the detector at the end is able to locate the tag with a precision of 2,5 cm (claimed)



I hope someone is able to guess how this device is working, at least in line of principle, or how is possible to achieve a similar result,even with a different technology.
In short what I am thinking is a system in wich th ereceiver is able to "understand" if the tag (transmitter) is within a certain area in front of it and not merely elsewhere around.

I don't need a so miniaturized system but a portable one.Not of the size of a big triangulator device.
Best of all would be if there is some ready made schematic.

Thank a lot for any help. Question
 

dknguyen

Well-Known Member
Most Helpful Member
I think only inexpensive IR will work if you want the receiver to see the transmitter only if it pointed right at it. Microchip has very easy to use infrared IC chips that automatically modulate/demodulate UART messages to/from IR so you could use that to uniquely identify objects and know if you are pointed at the object. But you need line-of-sight.

An RFID tag will make a very simple transmitter, but if the transmitter is the passively-powered kind (not the actively-powered kind), your range will not be very far (but then you don't need batteries for the transmitter!). But it would transmit in all directions. Instead of knowing the direction the object is in, you would be able to tell when you are near it though. You could also have it beep faster as the signal got stronger so you could know how close you are to the transmitter.
 
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elctrified

New Member
Thank for reply dknguyen,
you have well pointed the few problems I have encountered and that's why I decided to try to find help in some specialized forum like this one, I hope so at least.

As I told, I have found this device I have mentioned in the first post, after many many hours searching, and this device perform the most close, unluckely but they do not disclose any tech detail so I am wandering still in the dark.

Maybe I am ingenuous but I think that if they have found a solution and it is packed into a so a small device, it must be not so complicated, it must be a very clever implemetation of some technique.... that's why I am interested first of all at the working principle, after have guessed the principle then the technical side should be more easy to solve.

My brain is smoking at the moment.
 

dknguyen

Well-Known Member
Most Helpful Member
What are you trying to do exactly? Search for items? Because then IR won't work all the time because you need line of sight. I would go with RFID to tell me how close I am to the object (rather than its direction) because that works just the same and because you dont need line of sight.

Its not that complicated it seems. Just a radio tag. You should be able to do it on your own...they just get to use custom boards and tiny components.

If you could find a way to use a YAGI antennae to detect an RFID tag signal (or you could make your own radio transmitter) then you would have directionality since the YAGI attenaes are very directional and very sensitive in that direction.
 
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elctrified

New Member
The idea behind this project is to transform the signal detected into a digital signal and then to represent it graphically on a x-y coordinate plan on a computer screen.
Eventually I could have the Z coordinate represented by the strength of the signal.
I think that with a device like the one I am talking about (but tell me, did you look the link?) if it would possible to estabilish a radial angle of sensitivity (that would represent the plain working area) then the emitter tag would be localized by the intensitivity of the signal.....
With an a/d converter should be relatively easy, with a certain degree of aproximation) to represent the situation on a computer.

Of course I would build either receiver and transmitter...
Yagy antenna? Unless it is possible to build a few centimeters yagy, I have already precised I am talking about a portable device.
Do a micro yagy would work? (I hope you know what you are talking about (with no offence, just I am not willing to waste my time and other's time)
 
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dknguyen

Well-Known Member
Most Helpful Member
Yeah, I looked at the link. That's why I was wondering if you needed to be able to detect the tag without line-of-sight, because if you do the nice super convenient IR method does not work.

The smallest Yagi's I have seen are pretty small, they are hand held but maybe a bit too big. They seem to be around 60cm which is probably a bit bigger than you want, but I haven't been really searching for antennas. I think I saw one that was 8" once. From what I can see the small Yagi antennae frequencies are much higher than a typical RFID tag which is good I guess since it would make for a smaller antennae. So if you go that route, you'd need to build your own RF transmitter.

Looks like this:
**broken link removed**

I honestly don't know how they mapped out the angle and distance of the RF signal since power is affected by distance and by whatever is between the transmitter and receiver unless they somehow built a directional antennae into the handpiece. From reading the website it says that RF and RFID tags are used.
 
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elctrified

New Member
Do you have a link or can show me what kind of yagi is the 8", (that's 24-25 cms, right?) If it would be a stilus like, it would be good, I a telescopic one would fit, but if it has to be similar to a TV antennae then I can't go this way, it would be unpractical.
But then, they(those of the lo8tor) don't (apparently ) use any antenna.

BTW, I wonder if I am on the right path with this, maybe other solutions are available, at the end this device is not much far from a radar , dont missunderstand me, I mean in line of principle.....

Isn't that you have any alternative idea? (Remember the goal is to represent it on a screen)

I apologize if my english is bad, I am trying to do my best but tech reasoning is quite hard to translate in words for a non engish mother tongue.)
 

dknguyen

Well-Known Member
Most Helpful Member
I understand what you are trying to say.

I'm sorry, I can't seem to find the 8" yagi antenna anymore (I do not even remember it clearly, 8" may have not have been the length of the antenna and another dimension).

If I were you, I would use regular RF to know if you were far or near and then use IR to tell what direction in case you have line-of-sight. Because IR is the best for narrow detection angle, except that it IR cannot travel through things. It would use RF to tell you if you are near or far, and it would use IR to tell you the direction (if it can see the IR). Maybe you can use a regular antennae and shield it on 3 sides so it could only receive signals from one direction?
 
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Nigel Goodwin

Super Moderator
Most Helpful Member
dknguyen said:
I understand what you are trying to say.

I'm sorry, I can't seem to find the 8" yagi antenna anymore (I do not even remember it clearly, 8" may have not have been the length of the antenna and another dimension).

The size of a yagi is dependent on the frequency of it's use, and it's length is dependent on you much gain and directivity you require. There are plenty of internet sites which will calculate you any type you need - but an 8" long one is going to be very high frequency.

Looking at the specs for 'loc8tor' it uses the 2.45GHz ISM band, so it will use pretty small aerials.

However, reading the website a little leads me to believe that elctrified doesn't understand how it works, and that it doesn't do what he thinks it does!. It doesn't give you a nice 2D plot of where an item is located, accurate to an inch or so - it's just a DF (direction finding system) and you follow it for maximum strength until you find the transmitter.

It's not a 'lot' of money, why not buy one and experiment?.
 

docel

Banned
yAGI

Yagi calc:L
Electrical 1/2 wave length (in ft)= 468/Freq. in Mhz.
(The electrical length is corrected for velocity factor of the metal and is different from wavelength by calculation)
 

elctrified

New Member
However, reading the website a little leads me to believe that elctrified doesn't understand how it works, and that it doesn't do what he thinks it does!.
It doesn't give you a nice 2D plot of where an item is located, accurate to an inch or so - it's just a DF (direction finding system) and you follow it for maximum strength until you find the transmitter.
I think I understand the purpose of this device.
I never said that it do plot, I said that this function must be implemetend in my own (that is the goal of my project)
If I could find any solution that allow me to have an external object to be detected and its position plotted on x-y axis I would go for that. If you know something about that please just let me know.
Even if you only have heard about it,or if you know how it could be called such a system I would know it, because at the present I don't even know what keyword to search for.

Any help for that is really appreciated .

It's not a 'lot' of money, why not buy one and experiment?.
well, as you have read on their site is not yet on the market.
Then I think that even buy one I am not shure I can understand the principle of working, even openin the box. The schematics would work for that.

. Maybe you can use a regular antennae and shield it on 3 sides so it could only receive signals from one direction?
Interesting thought, if you know it, can you tell me how to shield an antenna (just the principle) it would save me some time in searches for that.
I also thought to an antenna L shaped, or a microparabolic one,but I couldn't go more far than a thought.
 
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dknguyen

Well-Known Member
Most Helpful Member
Shielding

I think you can just shield antennaes by sticking them metal box with one side removed. Just make sure that the metal walls aren't too close to the antennae- I just read that as a requirement for an RC antenna once.
 

i_build_stuff

New Member
The only way I can think of to get an X-Y plot will be to use two or more orthogonal pairs of even-multiple frequencies, and measure the phase shifts between them. Maybe use a frequency divider on the higher one and a phase comparator like the ones in PLLs. Each frequency pair will give you an infinite set of solutions, but with two or more pairs, the solutions should only line up in one spot. That will probably be the easiest way to measure the time delay from antenna to antenna (since the signal is travelling at the speed of light).

Getting the angle will probably require three antennas, laid out like an asterisk (with a horizontally polarized signal).

You'll have to feed both sets of results into some kind of DSP to extract the information. This could be a high-end microcontroller (like the ARM series), a small FPGA, or just a computer. Of course, that same chip can also display the results on an LCD for you.
 

elctrified

New Member
thanks I-build-stuff
good matter for investigations.

Do anyone has an idea how to define such kind of device?
I have already tried hundred definitions and googled each one with no appreciable result.
The problem is that not being me english mother tongue it is a little difficukt, also babelfish sometime seem to me stoned fish, I've got some funny translation.

thanks for help.

Cool people here.
 

philba

New Member
google for "radio direction finding"

radio hams (amatuers) do this all the time "fox and hounds". lots of circuits out there - google is your friend.
 

elctrified

New Member
hey, thanks for advice, I will google that as soon!

BTW, I was talking in line of principle, not about radio signal especifically, but about this thing of detecting and plotting the position of an object (could it be also a signal, a radio) on a pc screen.

I have the sensation I have seen some application, maybe long time ago, but I couldnt remeber, it is like I cannot focus my mind on that.(may be I have dreamed it once...)

Perhaps was an application with trought a camera....dunno.

If it was made throught a camera in such case we would have a light signal that is detected by the ccd sensor.
could be an alternative, why should I use for istance an IR , with or even a RF system, a camera would be much more precise, and even I would have the unique ID from the source.

(don't worry I am thinking loud)
Say that I move a stick with a red pulsing led on top of it, in front of a camera, the unique ID of the object coud be derived from the color of the led and of the frequency of the pulses....

It could be an alternative system isn't it?
Again I would perform some search in this direction, any suggestion what to search for?

Don't think I am crazy now, please, as I have explained I am looking for a solution at this stage of the project and of course I am looking for something clever, not usual.

Thanks all the beautiful minds here!
 

docel

Banned
Triangulation.

Hello,
You can try Ultrasonic beams, and do what the Bats do...Triangulation. Search for Devantech SRF04.
Now any position can be found out by triangulation. If the source is a transmitter at some position , Two sensors/Receivers seperated by a finite distance will measure two distances. This will give you the position and can be determined using software.
Alternatively, the 3 sides closed enclosure will make the sensor/receiver directional. If using a light source there is a reflector which will focus the light in one direction. It is the same whether Light, Radio Frequencies, Ultrasonic or Sound. A concave cavity with the sensor placed at the focal point will be a good starter.

Wonder if at all you saw my formula ? The Yagi has three 1/2 wave elements.

Of the 3, one is 5- 10% less and the other is %-10% more in length, as calculated by the formula.When separated by a 1/4 wave length, this antenna Yagi-Uda) will receive better in one direction (with gain). The longer element is the reflector; prevents signals and reflects it back to the central 'Radiator' The Smaller element 'Directs ' the signal in that direction. This 'amplifies' the signal and is called Gain.
One thing: Any RF directional antenna will work only at a distance (approx 100 wave lengths) and become 'useless' as it nears the Transmitter.....( the receiver will "receive even without any antenna attached!). A comination of Gain, Null and attenuator/offset techniques are used. (You must have already Googled for RDF antennas by now.)

Other possibilities are to put a sensor in a tube: it will receive signals only from 1 direction. Light, Sound or Ultrasonic.

There are other uses: RFID principles, Near-Field communication etc.,


https://www.electro-tech-online.com...-triangulation.20791/?highlight=triangulation

https://www.electro-tech-online.com...ce-measurement.20273/?highlight=triangulation

Now, Think you've spent enough time on the net. Just get down to work and let us know how it goes!!
 
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elctrified

New Member
Hi docel
grrrr, I had wrote a long , nice answer to reply to you in a nice manner to let you know how much I have appreciating your support, but accidentally Istroke the return key and ....everything disappeared.

Now I don't want to start again and will resume briefly it.

Ultrasonic, too short range, 10', I need 330', plus other issues.
Alternatively, the 3 sides closed enclosure will make the sensor/receiver directional. If using a light source there is a reflector which will focus the light in one direction. It is the same whether Light, Radio Frequencies, Ultrasonic or Sound. A concave cavity with the sensor placed at the focal point will be a good starte
wolud you explain that a little more? I cant figure out, but what dimension for that device?

I have searched for RDF, I come across all the sites I have found with radiotrigonometry, radiogoniometry keywords at the beginning. Was during such searches that I encountered the loc8tor :)

I have found a producer that is able to build antennas printing them on a thin plastic film, I think I will look also this direction. THought I am not convinced that there is not some more specific for my goal.
I will review the link you kindly provided, thanks a lot for that!

Now, Think you've spent enough time on the net. Just get down to work and let us know how it goes!!
true, I have spent a lot of time, well not really so much, what I could in my little spare time, but it doesnt mean I am ready to go work,would be too much cool hahaha

thanks again.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
I think you've been watching too many James Bond films?, your project is extremely difficult to try and do in the first place, then you have an incredible accuracy requirement as well.

I'm doubtful you can get it to work at all?, but i'm absolutely positive you'll never get anywhere near the accuracy you seem to be hoping for.
 

docel

Banned
Deplorable...!

Nigel Goodwin said:
I think you've been watching too many James Bond films?, your project is extremely difficult to try and do in the first place, then you have an incredible accuracy requirement as well.

I'm doubtful you can get it to work at all?, but i'm absolutely positive you'll never get anywhere near the accuracy you seem to be hoping for.

PLEASE DONT DISCOURAGE PEOPLE. The least one can do is keep quiet, if you cant help. People visit the forums for help and guidance.
As a Moderator you need to be moderate with the people you are trying to moderate. As an instructor, one must indulge in the young and inexperienced and guide them towards a goal. And Electronic gods should......well be Godly!!:(

Electrified, you can browse the other thread. It is similar to your needs and more sane than this thread. The same things are being dispensed there.

https://www.electro-tech-online.com/threads/ultrasonic-range-penetration.21503/#post137889

I somehow feel that this thread will "disappear" with reasons like
""The Electronics Projects Forum is for completed projects ONLY, and for their discussion, NOT for posting other things - your posts have been deleted.

Moderator.
__________""
 
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