Melody Generator Using IC UM66:
IC UM66 is a small transistor type IC with 3 pins. It is a ROM IC with a prerecorded music inside. When power is applied, IC oscillates and its output gives the music notes. It is necessary to amplify the output in order to hear through the speaker. For this, a single transistor amplifier is sufficient. IC UM66 works well in 3 volts but the power supply can be up to 4.5 volts. So a Zener diode based regulated power supply is used. If the supply voltage is 3 volts (2 pen cells), there is no need for the zener and the power supply can be directly connected to the IC. Here 9 volt battery is used to get loud sound. When power is applied, IC oscillates and the sound can be heard through the speaker. You can use a small 2 inch (4 ohms) speaker or a Mylar speaker (one used in toys). It can be used in toys and door bells.