Sensor & Relay

[rongster]

I am thinking of a simple project.

I have a active 3 yr old boy. Am thinking of a making something that works similar to that of an alarm system.
My idea is my boy will have a sensor on him (e.g. rfid/infra red/bluetooth, etc) and i will be holding the recevier. Once my boy is separated from me for about 10meters, the alarm on my boy will sound, making it easier for me to locate him in a crowd. i find that it will be useful when my family travel overseas or to unfamiliar place.

My problem is,
1) Is there such a small sensor like component available?
2) When we are seperated, how to active the alarm? Using a relay?
3) Any other smaller alternative than using a bulkly relay?

Any expert here? Pls advise.
Thanks

 

[jpanhalt]

You mean like this:






John

 

[rongster]

Thanks jpanhalt

Do you have any idea what technology they are using?

 

[st1f1]

this is a ir light barier...the only problem with it is that it will go on everytime a person walks between your son and you **broken link removed** i guess mobile phone is a better solution

 

[rongster]

Thanks st1f1

Is there a similar product that is handphone operated? Are you refering to bluetooth?

Thought of creating it myself, for the fun of it. It can be a very simple DIY circuit.

 

[Gordz]

I saw a car alarm project once that had a low power FM transmitter with a 10khz tone generator on the input. A pocket FM radio was modified so that whilst it recieved the tone a relay was held in the off state. When the tone dropped out a relay energised and set of a siren.

Something similar to this could work.

I think a better way is for you to have the transmitter and your son has the reciever. If he goes out of (or is removed from) range his unit will sound a loud beeper allowing you to find him quickly

 

[st1f1]

well, this store where i got this schematic also sels a product that can be something like mobile phone operated, it's not that expencive, but even better, if i can find the scematic of it on the internet, you can make it yourself, the only problem it is that i don't really know if it will do what you want...you'll probably have to add a relay circuit for the alarm or something like that. i'll try to find it

 

[rongster]

Thanks st1f1

The schmetic will be a great help. I look forward to ur reply.

 

[st1f1]

it seems that while the circuit is rather simple, it requires another mobile phone. you call it, and the circuit detects it is ringing (none needs to answer it, so it won't cost you anything to make the call) and turns something on/off.. can't find the schematic, i but i know they have it in store, something like this: **broken link removed** i am sorry but i can't find the schematic at the moment

 

[KMoffett]

There are many commercial versions of the child/luggage/brief case proximity alarms out there with a broad range of prices. Like this one: Child Proximity Alarm(w ID)

But, then again it's not always about buying the solution.

Ken

 

[Andy1845c]

In this case I think I would just buy a solution. Its not going to be a great beginner project. Its too complicated. Plus you want both the part you carry and the part the child wears to be lightweight and durable. You don't want bulky relays and heavy batterys.