Help developing rf theft detection system.

[amirivija]

As a part of a project, I am interested in developing a rf based personal belongings theft detection system.
The RF transmitter module would be placed with the personal belonging to be monitored (eg : luggage in a train/ laptop bag / etc), the RF receiver will be placed with the person. Once the system is activated and the RF transmitter placed in the personal belonging goes out of range, the alarm with the person will start ringing.

The system should have the following features:
1. I should be able to track upto 6 personal belongings. The number of belongings being tracked would be specified by the user.
2. If two or more systems are under operation within the radius of the receiver range, the system should work as desired.
3. The cost of the system must be very low. (less than 10$).
4. The battery life should last for long
5. The alarm must ring whenever any of the tracked belongings goes out of range.

Since I have a background of mechanical engineering, I am not an expert in designing the system I am interested in.

Based on initial reading and other posts in the forum, I understand that rf transmitters and a receiver programmed using a micro-controller could do the trick.

This is my first post on this board, and I am looking forward for help in any aspect..

 

[GrandAlf]

RFID may be the solution for short range. There are similar devices already to stop children straying too far away, but I think they use conventional low power public band radio. I am pretty sure I have seen commercial units that do what you require, cannot remember where though, or indeed the cost. Its an idea thats been around a fair while now.

 

[amirivija]

Thanks Grandalf..
As you suggested, I looked around for and found a https://www.mommyimhere.com/ child locator which is similar to what I am looking for. It is pricey though.. around 35$ as well as it has a large range (250 feet) which is much larger than the range (5m / 16 feet) that I am looking for..

I also need to track upto 6 bags (Transmitters)
Hence, I guess that I need to have a custom build circuit.
Based on some more reading, I understand that I should make use of a PIC micro-controller to program the system.

It would take quite some time for me (3-4 months) for me to come to speed and try to implement this system on my own ..

Since I need this system earlier than that ..

I am also willing to provide money as a token of appreciation for help in designing and developing the system.

 

[GrandAlf]

Maybe it is worth while to do a little more searching. I am certain I have seen a commercial system exactly as you describe. If I can remember where, I will post back.

 

[kad_911]

well for 1 bag i could simply be done using a RF receiver and transmitter with a PIC(s). when the 2 units are in range, nothing will happen but when it goes out of range, the PIC can detect that as an interrupt (or just input) and trigger whatever the alarm you need.
im not sure how to do that for 6 bags unless you have 6 transmitters + 6 receivers.

 

[Rob B]

MuRata were doing a RFID device which may be suitable for this. It had a good range and due to it being capacitively coupled to the antenna makes it easy to mount. I think it was a chip-scale device though, you may still have luck with it.

I thought of somethin very much like this years ago but transponders were more limited in range.