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# finding object location in the room

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#### koyeh182

##### New Member
can somebody tell me how to get an object location in a room. just 2D coordinate. pls...

koyeh182 said:
can somebody tell me how to get an object location in a room. just 2D coordinate. pls...

If it is your TV remote you are looking for, give up now, there is an unknown law in physics that prevents finding it. :lol:

Seriously you need to provide a lot more information there are so many ways to map a room to find an object.

-Latitude/Longitude will give you a global position of your room and anything in it.
-Fixed reference point from/to in degrees to ref/object and distance.
-You can divide your room into a grid and have x y coordinates
-you can tie a string to the object so your object location is "other end of string"

Let us know what you are tring to do an maybe we can help you a bit better.

finding object location in a room

It sounds like a transmitter / receiver circuit request 8)

I got a kick out of your other suggestions, especially the coordinate grid.

Here's a whistle reponder circuit.

dingo said:
-you can tie a string to the object so your object location is "other end of string"

Depends on wich side of the string you are... :lol:

my project is about an one button remote that can switch on or off the light, fan or something else. This remote will send its current location, height and its direction to the server and then this server will on the light witch the remote is pointing at. hopes that you all can give me an idea how to make it.

That is not an easy project

If these items that you wish to switch on/off were mapped then the easiest way would be with 2-way radio and a compass inside the remote.

You press the remote and it transmits and receives to your base station, you can measure the timing to give you the distance the remote is from the base. This will give you a circle of a defined distance. Now the remote sends the compass reading to the base station combine that with the known circumference draw a tangent off the circle in that direction. Hopefully there will be only one controllable item that will met that criterion.

You could set up a second base transceiver this will give you a lot more accuracy instead of being anywhere in a circle there are only 2 places you could be standing and a 3rd transceiver would narrow that down to one. If you continue further and add a 4th on the roof you can get the height. Install a gyro or just weight the wheel from the inside of a track ball mouse can give you the azimuth as well.

{edit} PS take the compass reading before you transmit as it will throw the reading off. Also magnetic north moves so you will need to correct every few years.

thanks a lot dingo.

for the location sensor, may be i'll be use your idea. that mean, i need 4 transciever. but, how could i get the radius of the circles. can i use the signal strength to get the radius or is there other way to calculate it ? if i this method, how can i get the signal strength from the circuit ?

i would like to use component from this web site : www.rentron.com
for the 8 bit encoder and decoder, may be i'll use HT-640a and HT-648L.
ok. so, from this component, can i measure the signal strength?

i made a mistake you only need 3, say one north, south and on the roof.

You can tell distance by timing

have the remotes and base station receive and xmit of diff freq

remote calls base 1
base one transmits a signal that the remote is feeding back into its xmitter
base 1 times how long it takes the pulse it xmitted to get back .00234 of a sec therefore the remote is 5.43 meters away (don't use those figures i made them up). This is how laser range finders and ultra sonic tape measures work.
Remote calls base 2.......
Remote calls base 3.......
remote sends bearing
remote sends azimuth

By knowing the 3 distances, bearing and azimuth of the remote you can work out exactly what you are pointing at.

Just a little more info on range finding with radio, you are timing the speed of light that is just under 300,000,000 m/s. This is fast most likely faster than you will clock your micro controller at, so you will have to find another way to measure it.

Also your carrier will need to be faster than the smallest unit you are going to measure say around 400 mhz because you don't want your carrier slower than what you want to measure. It can be done because you can buy laser range finders off the shelf and they use speed of light to calculate distance. You could possibly use a PLL to clock to some analogue storage, maybe use a 400 mhz > clock to pump up a cap during the timing window then read the cap voltage?

If line of sight is not a concern then you may want to look at ultra sonic transceivers as the speed of sound is a lot slower and easier to clock.

Whoa................dingo, it sounds like you know what you're talking about! :shock: I got lost! I'll be sure to remember you next time I need help! :lol:

if I use that method, i need a verry fast processor and this will make a high cost project. isn't it ?

my project doesn't have enough budget. So, i need to use a low cost component. Thanks a lot dingo!

but, i have read an articles about finding location using signal strength.
I think, this is the best option. But, my problem now is how can i get that value? I don't remember who worked on this project.

The project is not an easy one, your processor does not need to be fast but whatever you use to capture the length of the timing pulse will have to be very quick.

Using signal strength is a one way but it creates a lot of variables. You can use an op amp to measure you signal strength just, measure the voltage of your carrier signal at the receiver.

The problems you will face are general problems with radio, you could move a few feet further away from the receiver yet improve your signal. If you have ever tried to tune a tv with rabbit ears you will know what I mean, moving the antenna closer to the tv station does not help much. If you do try something like this use a low freq. This idea could work in a large open area but I doubt the readings will be constant enough to work one day to the next. I would suggest you use this method if you only want to know what room in the house you are in, not where in the room you are.

There is another way to triangulate your position by using directional finders. You will have to move the aerials on you receivers to get a bearing though.

Can you mount 3 transducers on the walls and ceiling?

Why do you need to know where the object is? are there other devices that can be turned on and off? It would be easier to code the signal so only one will respond. This may require more than one button, but why limit yourself to one?

everyday, people become lazy.. hehe!! :lol:
just kidding.

if we use multibutton remote, we have to remeber witch button for lamp,
button for fan, and so on. but with one button remote, user just point the thing that he want to turn it either on or off. that's my idea.

i want to make our life easier. that's all.

i would use something to concentrate the beam like a laser for the transmitter that way only one reciever recieves the signal. but you might have to space them out a little.

thats right.
but using laser is big cost.
small laser just can measure a verry short distance.

if i use rf device, what type of rf should i use?
is't fm or am ?

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