Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
I want to build a personal alarm that have a transmitter and receiver.
eg, if your child has the transmitter and move out of range maybe 10m then the receiver must sound to alert you!
There's a lot of ways to do this but all have their problems and the more reliable the system the more expensive and complicated it will be. Your thoughts might be to transmit and RF signal - it will work but the range will be extremely variable and you need to be licensed to transmit.
I have to wonder if PDAs or other devices with Bluetooth/other wireless link capability can't be configured so that one queries the other every 10 seconds or so - the other responds. A failed response would sound an alarm on the PDA.
The kid is 2m from you which is well within its range. Then somebody walks in between and blocks the signal and the alarm rings.
The kid walks only 1m away behind some metal shelves in a store and the alarm rings.
So your project also alarms when there is an obstacle in between. Not good.
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