Proximity detector circuit - Electronic Circuits Projects Diagrams Free

craigey1 · 20th November 2007, 07:57 PM

Hi all,

I was hoping someone might be able to help me with a little project. I'd like to build a small proximity detector that can detect (flash an led or beep etc) when a copy of the circuit is in a range of about 10M.

I know this would require a transmitter & reciever running continuously within the same circuit. I presume there would also need to be something that would tell it to ignore signals that are too strong, otherwise it would continuosly detect itself.

I was thinking a small bluetooth-type of device would do the job.

The idea is that a group of random people could each carry one with them, while they walk around in a public place & have to find each other. It's sort of a life based game where players chat online & so never actually see each other until the circuit tells them that another player is nearby.

Thanks in advance

blueroomelectronics · 20th November 2007, 08:53 PM

They sold those things in Japan several years ago.

Darth Bagel · 20th November 2007, 11:11 PM

Bluetooth seems like serious overkill for that application.

Leftyretro · 21st November 2007, 01:40 AM

Interesting application. I guess some form of time multiplexing where a given device listens for say 90% of the time and broadcasts for the other 10% of the time and they rely on the fact that the devices are not synchronized so messages are bound to get through in short order. 10 meters is not a demanding distance.

Not a lot of information has to pass between the devices, but a short FSK ascii message (send "HI") might help prevent false positives from interfering sources. A simple PIC with those cheap FSK transmitters/receiver modules might fill the bill. PIC turns on a cheap buzzer when it receives a valid message.

http://www.sparkfun.com/commerce/pro...roducts_id=872

Lefty

craigey1 · 21st November 2007, 10:45 AM

Brilliant. Thanks for that.

I was thinking a lot more about this last night.

For Instance it could use USB to charge a small rechargable battery & have an interface where you could enter your details & the details of who / what your looking for.
eg: I could enter my details as tall dark & handsome & I'm looking for a single tall blonde slim woman. One day I'd get a buzz from the device & would know that she is single, so I'd feel far more comfortable with asking her out. Alternatively she may get a buzz & notice Mr. TD&H.

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20th November 2007, 07:57 PM	(permalink)
craigey1	Proximity detector circuit Hi all, I was hoping someone might be able to help me with a little project. I'd like to build a small proximity detector that can detect (flash an led or beep etc) when a copy of the circuit is in a range of about 10M. I know this would require a transmitter & reciever running continuously within the same circuit. I presume there would also need to be something that would tell it to ignore signals that are too strong, otherwise it would continuosly detect itself. I was thinking a small bluetooth-type of device would do the job. The idea is that a group of random people could each carry one with them, while they walk around in a public place & have to find each other. It's sort of a life based game where players chat online & so never actually see each other until the circuit tells them that another player is nearby. Thanks in advance

20th November 2007, 08:53 PM	(permalink)
blueroomelectronics	They sold those things in Japan several years ago. __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com

20th November 2007, 11:11 PM	(permalink)
Darth Bagel	Bluetooth seems like serious overkill for that application.

21st November 2007, 01:40 AM	(permalink)
Leftyretro	Interesting application. I guess some form of time multiplexing where a given device listens for say 90% of the time and broadcasts for the other 10% of the time and they rely on the fact that the devices are not synchronized so messages are bound to get through in short order. 10 meters is not a demanding distance. Not a lot of information has to pass between the devices, but a short FSK ascii message (send "HI") might help prevent false positives from interfering sources. A simple PIC with those cheap FSK transmitters/receiver modules might fill the bill. PIC turns on a cheap buzzer when it receives a valid message. http://www.sparkfun.com/commerce/pro...roducts_id=872 Lefty __________________ Measurement changes behavior Last edited by Leftyretro; 21st November 2007 at 05:14 PM.

21st November 2007, 10:45 AM	(permalink)
craigey1	Brilliant. Thanks for that. I was thinking a lot more about this last night. For Instance it could use USB to charge a small rechargable battery & have an interface where you could enter your details & the details of who / what your looking for. eg: I could enter my details as tall dark & handsome & I'm looking for a single tall blonde slim woman. One day I'd get a buzz from the device & would know that she is single, so I'd feel far more comfortable with asking her out. Alternatively she may get a buzz & notice Mr. TD&H.