How can I build an door alarm that sends a signal wirelessly to buzzer maybe 30m away when the door is opened?
I need to hear the front door open from quite a way away and I can't really run wires all the way. The signal would need to travel wirelessly from the front door of my business to the buzzer at the other end of the premises.I can't seem to buy a pre-made version nor a kit for this anywhere! Would there be a way I could use a kit with a reed switch ie magnetic sensor on the door but somehow wire it to a transmitter instead of a buzzer? Then I'd need a receiver connected to a buzzer I suppose. I've no idea really where to start.