Check out this excellent audio doorbell project created by Adafruit community member Jarruda — with a little help from the Adafruit forums!
So when I bought my house, I noticed it had probably the most boring doorbell on the planet. Then I saw the Adafruit’s Wave Shield and saw inspiration. This is my first actually completed hobby electronics project, so I’m pretty proud of it, even if it’s really simple.
Power for the doorbell comes from a 16V transformer off mains power (120V). It’s run through a 50V 4A bridge diode rectifier into an electrolytic cap and a ceramic cap to smooth the pulsed DC, then two diodes to drop the voltage by ~3V before powering the mono amplifier and being split off for the UNO’s Vin.
The doorbell is connected like any other button, sending 5V out to the doorbell and in to a digital pin configured as an interrupt. Using a pullup resistor and pulling the pin to ground wasn’t used to lower the demand on the linear regulator running on voltage that’s a bit higher than I’d like. To further reduce power usage, the atmega328 is put into PWR_DOWN sleep in between doorbell rings.
Also, thanks to adafruit_support for providing help!
My next project is a little more ambitious, a thermostat that can use a wireless sensor for temperature readings.