Very short range wireless communications methods.

[Brad Kartchner]

Hello everyone.

I hope the collective wisdom of this group can aid me.

I am working on a project made up of a series of base stations with an
associated mobile tag for each station. The idea is for a base station
to be able to respond when its associated tag come in range.
Unfortunately, I'm relatively unfamiliar with wireless communications
and have been unable to find a suitable solution.

My requirements are:
--------------------------------------------------------------------
The base stations must only detect tags within 1/2 to 1 foot of them
(although a slightly smaller range may work also).
The base stations must be able to distinguish its associated tag from
any others.
The tag must draw as little current as possible (I'm planning on
powering it with a 3V coin cell battery).
Cost is a factor - cheaper is better (obviously).
--------------------------------------------------------------------

RFID would be the ideal option, except that readers are so $%&!
expensive.

I've looked into simple Infrared communication, but realize that
limiting the communication range would be troublesome and unreliable.

I've toyed with the idea of RF communications, but again, it seems
difficult to reliably reduce the communication range, since most
manufacturers want to MAXIMIZE range!

I'm intrigued with the possibility of using magnetic fields, but don't
really know what direction to go to pursue this.

Basically, I've just about reached the limit of where my knowledge and
research capabilities can take me. If someone here could, at least,
point me in the right direction, I would greatly appreciate it!

 

[amdx]

Hello everyone.

I hope the collective wisdom of this group can aid me.

I am working on a project made up of a series of base stations with an
associated mobile tag for each station. The idea is for a base station
to be able to respond when its associated tag come in range.
Unfortunately, I'm relatively unfamiliar with wireless communications
and have been unable to find a suitable solution.

My requirements are:
--------------------------------------------------------------------
The base stations must only detect tags within 1/2 to 1 foot of them
(although a slightly smaller range may work also).
The base stations must be able to distinguish its associated tag from
any others.
The tag must draw as little current as possible (I'm planning on
powering it with a 3V coin cell battery).
Cost is a factor - cheaper is better (obviously).
--------------------------------------------------------------------

RFID would be the ideal option, except that readers are so $%&!
expensive.

I've looked into simple Infrared communication, but realize that
limiting the communication range would be troublesome and unreliable.

I've toyed with the idea of RF communications, but again, it seems
difficult to reliably reduce the communication range, since most
manufacturers want to MAXIMIZE range!

I'm intrigued with the possibility of using magnetic fields, but don't
really know what direction to go to pursue this.

Basically, I've just about reached the limit of where my knowledge and
research capabilities can take me. If someone here could, at least,
point me in the right direction, I would greatly appreciate it!

How about the sensors used to identify cows at a feed station.

http://www.id-ology.com/products/?productcategory=Dairymen

http://www.mainelynupulse.com/milking.html#cowid

Just a thought.

 

[Luhan]

Hello everyone.

I hope the collective wisdom of this group can aid me.

I am working on a project made up of a series of base stations with an
associated mobile tag for each station. The idea is for a base station
to be able to respond when its associated tag come in range.
Unfortunately, I'm relatively unfamiliar with wireless communications
and have been unable to find a suitable solution.

My requirements are:
--------------------------------------------------------------------
The base stations must only detect tags within 1/2 to 1 foot of them
(although a slightly smaller range may work also).
The base stations must be able to distinguish its associated tag from
any others.
The tag must draw as little current as possible (I'm planning on
powering it with a 3V coin cell battery).
Cost is a factor - cheaper is better (obviously).
--------------------------------------------------------------------

RFID would be the ideal option, except that readers are so $%&!
expensive.

I've looked into simple Infrared communication, but realize that
limiting the communication range would be troublesome and unreliable.

I've toyed with the idea of RF communications, but again, it seems
difficult to reliably reduce the communication range, since most
manufacturers want to MAXIMIZE range!

I'm intrigued with the possibility of using magnetic fields, but don't
really know what direction to go to pursue this.

You can get Radiotronix transmitters and receivers for about $5 each
at Mouser. A real implementation would require a microcontroller at
each end - $1 each from Mouser.

Luhan

 

[martin griffith]

Hello everyone.

I hope the collective wisdom of this group can aid me.

I am working on a project made up of a series of base stations with an
associated mobile tag for each station. The idea is for a base station
to be able to respond when its associated tag come in range.
Unfortunately, I'm relatively unfamiliar with wireless communications
and have been unable to find a suitable solution.

My requirements are:
--------------------------------------------------------------------
The base stations must only detect tags within 1/2 to 1 foot of them
(although a slightly smaller range may work also).
The base stations must be able to distinguish its associated tag from
any others.
The tag must draw as little current as possible (I'm planning on
powering it with a 3V coin cell battery).
Cost is a factor - cheaper is better (obviously).
--------------------------------------------------------------------

RFID would be the ideal option, except that readers are so $%&!
expensive.

I've looked into simple Infrared communication, but realize that
limiting the communication range would be troublesome and unreliable.

I've toyed with the idea of RF communications, but again, it seems
difficult to reliably reduce the communication range, since most
manufacturers want to MAXIMIZE range!

I'm intrigued with the possibility of using magnetic fields, but don't
really know what direction to go to pursue this.

Basically, I've just about reached the limit of where my knowledge and
research capabilities can take me. If someone here could, at least,
point me in the right direction, I would greatly appreciate it!

possibly here:

http://www.nordicsemi.no/index.cfm?obj=menu&act=displayMenu&men=21


martin

 

[Brad Kartchner]

You can get Radiotronix transmitters and receivers for about $5 each
at Mouser. A real implementation would require a microcontroller at
each end - $1 each from Mouser.

Thank you, I should have thought to check Radiotronix, as I've had some
experience with them in the past. I think their devices have a greater
range than I need, but I'll check them out.

possibly here:

http://www.nordicsemi.no/index.cfm?obj=menu&act=displayMenu&men=21

That looks very promising, thank you very much. I'll look into that
more as well.

Thanks for the responses!

Brad Kartchner