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Because I have not tested all electronic circuits mentioned on this pages, I cannot attest to their accuracy; therefore, I do not provide a warranty of any kind and cannot be held responsible in any manner.
Doorbell with PIC
24. June 2007 - 15:30 — admin
This article describes the construction of the "audio sample playing doorbell".
If you want to replace your old dumb "DRRRRRRRR" doorbell with something more sophisticated, you can try this doorbell circuit. It can play short (ca. 3-4 secs.) audio loop. Circuit uses the PIC18F microcontroller and the 24FCxxx series serial EEPROM: Doorbell with PIC18F1220 and 24FC512 
(Sorry, only in Czech at this moment, I'll translate it to English soon, I hope).
The principle of operation is really straightforward: PIC takes periodically data from serial EEPROM and sends them to DAC (the R-2R ladder) connected to RB port. Created audiosignal is amplified by LM386 monolithic amplifier and played by 8ω speaker.
Here is a ZIP archive with the essential information you will needs for building this device - the HEX file with data for PIC, the schematics and the PCB layout (both in EAGLE format).