Light Music


Schematic from /www.electroschematics.com

At the heart of this circuit is the UM66 IC, a sound generator. The IC is a CMOS LSI designed for using in door bell, telephone and toy application. When light shines on the LDR, the resistance drops and sends a signal to the T1 transistor. Power flows through the transistor to the UM66 musical integrated circuit, and a note will be amplified by transistor T2 and fed into the 8Ω speaker. The IC is preprogrammed to generate certain frequencies. When powered, the melody generator is reset and melody begins from the first note.