positioning sensor

[sebas2mil]

I ask for the help of all you wise people

There is a device out there that parents have for their children that works in case the child gets lost.
The parent wears one and the child wears one and if they get apart for a certain distance an alarm goes off until they get back in range. I am looking for a way to reverse this process, so when one person goes too close to the other an alarm goes off until you are far enough.

Here is the trick it has to be in a situation where one person has the main one and lets say 3 other people have the other end and if they come too close to the receiver the alarm goes off on each individual one appropriately.

Does any one know what sensors these are or any idea how to make one or even a different way. The criteria is that it has to be small enough to clip to a shirt and maybe financially accessible to prototype.

If you have something in mind I rather you email me at sebas2mil@myacc.net but go ahead and post also that way people can see your idea

[Cjmovie]

You might want to give a call and see what Thinkgeek was up to.

http://www.thinkgeek.com/tshirts-apparel/interactive/a090/

[sebas2mil]

thanks this will help, but i want to know what it actually uses but ill research more into these super duper shirts

[BrentJ]

I would look at reversing the idea over who has the receiver.

I would make the person people have to stay away from wear the transmitter.
Then the other people would have a receiver that alarms when it picks up the transmitters signal.

On the receivers you would probably have to have an attenuator to cut down the transmitters signal to the range you want.

There are transmitters / receivers that work on the 433Mhz band used for telemetry. These normally don't have to have a licence and you can't transmitt continuously. But for what you want 1/2 - 1 second would work ok.

Just don't wear them in a hospital. In case they are using the frequency.

[sebas2mil]

thanks that really helps

keep them coming this is all good stuff

[sebas2mil]

I'm sorry I can't say much more about this the thing is that I am working with another person on this project and we do not want to disclose too much about the idea