PICAXE-based music box or doorbell

摘要

This project started out as a music box for a child but using a different program, it could also be used as a battery-powered doorbell. When pushbutton switch S1 is pressed, power is applied to the circuit via diode D2. The PICAXE program then starts and the first instruction is to send pin 3 high which turns on transistors Q2 & Q1, latching the supply on. LED1 then indicates that power is on and that switch S1 has been pressed. Pin 4 is pulled high via diode D1 to let the program know that the switch is on.