I’ve had a problem since moving into my new place that I can’t hear people knock at my front door. Sure I could get a doorbell at the hardware store, but those things stink. Instead, I thought I’d create a quick and simple Arduino and XBee based system to do it for me:
Doorbells are the 20th century version of today’s perpetually-interrupting cell phone. There you are, cooking a delicious dinner or reading a nice book when the doorbell rudely goes off in your ear. Sure, you’re glad to see whoever is at the door, but interruptions that chime can be so obnoxious. Needless to say, I do not have a doorbell.
The problem with the knocking system is that I usually can’t hear when someone knocks from my lab. I depend on Penny the Dog to alert me when someone is at the door. Except Penny sleeps most of the day. And then there are the delivery people (UPS/FEDEX) who can’t be bothered to knock, even if it is a next-day-early-AM shipment of parts from element14 that I am eagerly waiting for.
I decided that I’d create a project that solves all of my problems: a silent LED that flashes whenever someone approaches my door. It is based on a laser tripwire and will be able to run day or night, even in the bright Denver sun. And if the blinking LED is annoying, a simple button press disables the alert and resets the trigger.