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# Variable 3D Proximity/Distance Sensor With Feelings : what to and how to Answered

Greetings,
I would like to know if there is a simple way to create a Variable 3D Proximity/Distance Sensor.
When you think about "Proximity Sensor" you think about "Infrared", but IR proximity sensors only ''scan" a straight line and not a whole spheric space, so that is not the answer.

Detail 1: 3-dimensionality
Imagine this:
We have object A and object B. Object A has the sensor.
Object A would sense object B's distance to itself (A) regardless of the relative position between the two objects - it wouldn't matter if B was in front of A, if it was on top of A, if it was behind A, etc.

Detail 2: Variability
The sensor would sense a variable proximity/distance. It would know if the two objects were 1cm apart, π cm apart, 12cm apart, 50cm apart, etc.

Detail 3: Feelings :3
(Oh, Teh Loev)
Imagine again objects A and B.
Object A would only sense Object B's distance to itself. Not it's distance to a table, nor a wall nor your cat. Like if only Object A and Object B existed.

Here's the catch: both objects would have the sensor and they would sense eachother (again, not anything else), so I can't use 'things' that would interfere with eachother (like, I don't know, isn't there something like the adding of sound waves[read phrase bellow]? I'm only a high-school student...).
I thought about using sound waves (because they spread 3-dimensionally), but I don't know how I could implement that...

Outcome
This is an example of what the sensors could be used to after having the sensors built and the code written:
1: Object A senses B. Object B senses A.
2: If B is 50cm apart from self (A), light LED1. If A is 50cm apart from self (B), light LED1.
3: If B is 20cm apart from self (A), light LED2. If A is 20cm apart from self (B), light LED2.
4: If B is 5cm apart from selft (A), light LED3. If A is 5cm apart from self (B), light LED3.

As you can see, in this example both objects would do exactly the same...

Sooo....
How can I make such a PAIR of sensors that wouldn't interfere with eachother?

P.S.: I'm talking about making a circuit of my own or buying a sensor and implementing it in an external circuit of my own or whatever...

Thanks a lot.

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## Discussions

If you used colored led's as beacons you could use photocells with filters as receivers and you wouldn't have to go thru all that coding etc.  But it would probably not be really discriminating, meaning you might get false results more often.

1)
Try an array of IR sensors, perhaps 10 in a base circle, 5 above that, and 1 pointing up. Assuming the IR sensors cover an arc, which they will, you should be able to cover the full area by using one at a time quickly. You could avoid cross-talk between the nodes by using different patterns of IR signal.
A = 11001100
B = 1110011100

2) If you are looking for distance apart, there are a few wireless protocols that posess this ability. ZigBee can do this, and if you have several devices, they should be able to calculate their position relative to one another. If you were to make a single fixed positon device (or a device with GPS aswell) you could determine their absolute position.

As you said, sound, specifically ultrasonic, could be a better solution for you. In a similar manner to 1), but with less sensors, you could use ultrasonic range sensors (which can be made from parts, or purchased as a pair).

If you wanted to do this however, build up. Make a single distance measure, such as those used to measure rooms. You will then be in a better place to build a larger device, having gained experience of what does and does not work.

Also, be aware of temperature when using ultrasonic measures.