I would like to use RSSI to locate an object in a 3D space. The space will be a square box with transmitters located on the 4 corners. An object will be place at certain positions within the box and I want to be able to determine its location inside the box. Much like an internal GPS.
I would like to know what components (IC's?) I need to perform such a task.
Or if anyone else has any other more effective methods to acheive such a task your comments are welcomed.
Thanks,
Josh
since RSSI devices (most of them) can output analog for a project that you have in mind. a uC (microprocessor) would be suited for that. Look at the AVR line of programmable chips. You'll need a DEV starter kit and learn a little about programming. THey have chips that offer multiple ADC (Analog to Digital ) converters. With these chips, they have enough power for a HID (Human INterface device) or simply output some coded results to your computer via a serial port and write some software. You may also want to look at Rabbit core embedded processors. With those, the hassle has been taken out of making a board. etc.. look them up on line.
-- "I\'m never wrong, once i thought i was, but was mistaken" Real Programmers Do things like this. http://webpages.charter.net/jamie_5
When is your assignment due?
Do you have to use RSSI? How big is your box? Can you use any object?
One alternative way to do it would be with visual object recognition using a camera on each side of the box.
For using RSSI I would have thought that you would have to use 4 receivers and the object is the transmitter?
Dave.
RSSI will indicate only the received signal strength, not distance - and there are a lot of reasons why an accurate position indicator is impractical using only this method, especially in the near field of the TX antennas.
It certainly won't work for VHF and above. I have had some success with short range position indicators using 125 kHz sources. If that is feasible for you, please indicate the dimensions you are working with.
Frank Raffaeli
GPS doesn't use RSSI, of course.
Is the task you want to perform the use of RSSI, or the determination of position location with a box? What kind of accuracy do you hope to achieve?
Have you considered ultrasonic distance measurement?
Chuck
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The project is to locate a r/c boat in a roughly 2 to 3m^2 water filled box, hence the transmitters or recievers will only be on the 3 or 4 walls of the box.
It will need to be fairly accurate considering the size of the box relative to the size of the boat (i.e down to cm's).
We are also considering placing a webcam above the box and using image processing to locate the boat, however I thought we might get more accurate results using RSSI.
I hope that helps.
Josh
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"Josh916" The project is to locate a r/c boat in a roughly 2 to 3m^2 water
** Huh ??This is even LOONIER that I thought !!
** Well, you thought wrong....... Phil
This detail would have been useful at the start! So is it a 2 dimentional problem or a 3 dimentional problem? i.e. can the water level vary? If it can vary then you can use a simple water level meter and then turn it into a 2 dimentional problem.
Nope, not a chance. Visual object recognition is the way to go, with a water level meter if needed.
Dave.
"David L. Jones"
**The OP is utterly confused, he simply has no idea what " 3 dimensions" means.He describes a box in terms of square area ???
He says the box is "filled" with water - but is it ??
He talks of an RC boat - but is it really a RC submarine ??
Must be if the box is "filled" with water, RC submarines are available.
Ergo it follows....
The OP is a just another naive, code scribbler with ZERO comprehension of physics or electronics.
They are now in plague proportions.
....... Phil
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Josh,
Your idea has been tried by big governments with big budgets.
NO, it will not work.
If you care to read a little, you may find a not so cheap way of doing what you want:
google has lots of links:
good luck
If you find a way of getting this done, in any home made way, please let us know.
donald
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Thanks for everyones help, RSSI was mentioned to me by a fellow academic and I'm at the stage of researching its possiblilites.
He seems to think that it is possible.
I will keep looking into it as I also have a backup plan using the webcam.
--------------- AS FOR PHIL ALLISON I THINK YOU SHOULD LOOK AT THIS WEBSITE:
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This I would like to see.
I too tried in college to use ultra-sonic devices.
It was just too difficult to get a signal that would work.
I will admit the technology has improved 1,000 fold over the years.
However, physics has not.
Good Luck
I would be very interested in how you both get this done.
donald
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Josh, he is wrong. It can be done (sort of) on a larger scale, but at the small scale you are talking about it's just not possible as other posters have mentioned. You would be lucky to determine if the object is inside the box or outside, let alone its position inside.
Seriously, start your backup plan now. Then it just becomes essentially a software project.
Dave.
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Having done some more research today it looks like other posibilities include acoustic positioning or infrared positioning (e.g.
What does everyone think about the other technologies mentioned above?
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Go with the backup plan, usehhte webcam. Processing power is cheap these days.
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You are wasting your time, visual object recognition is the best method in this particular instance. All the other methods (RSSI, acoustic, and IR) require a transmitter on the boat and multiple receivers. Visual recognition on the other hand doesn't require any transmitter, will work with almost any size or type of object, is simple, fairly accurate, will most likely only require one receiver, and reduces the problem to essentially a software solution.
The decision is blindingly obvious.
Dave.
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Thanks for everyones help, especially David Jones, I will be going with the visual recognition. It was originally my first choice though, as you do, I wanted to exhaust all possible options before finalising the decision as you never know there might of been an easier, more efficient way.
Josh
I've worked on someone else's image processing software that used a camcorder to track a lizard's frame to frame movement down a small track ~1.2M long or so.
You'll need to correct for parallax unless the camera is very high above the tank, so having a X,Y marks around the edges of the tank would help.
Python and Python Imaging Library was used to convert the colour image to greyscale first and then to two bit black and white if a pixel was either side of a set threshold value. This gave a black background with a white moving object on it that could be scanned vertically in my case to give the amount of movement in pixels which was then corrected for parallax and converted to millimetres.
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