This neat little circuit can play 8 note tunes at any speed you want. You select the notes with 8 trim pots. The speed in selected through a ninth pot. The circuit draws very little power and can be powered by a 9 volt battery, with the addition of a 7805 regulator to power the TTL logic used.
|R1||1||10K Trim Pot|
|R2||1||1K 1/4 W Resistor|
|R3, R4, R5, R6, R7, R8, R9, R10||8||500 Ohm Trim Pot|
|C1, C3||2||10uF 12V Electrolytic Capacitor|
|C2||1||1uF 12V Electrolytic Capacitor|
|U2||1||7490 Binary Counter||74LS90, 74HC90|
|U3||1||7445 BCD To Decimal Decoder||74LS45, 74HC45|
|U4, U6||2||7404 Hex Inverter||74LS04, 74HC04|
|U5, U7||2||4016 Quad Bilateral Switch|
|U8||1||3909 LED Flasher/Oscillator|
|SPKR1||1||8 Ohm 500mW Speaker|
|MISC||1||Board, Wire, IC Sockets|
1. R1 controls the speed at which the notes are played. R3-R10 control the pitch of those notes.
2. The circuit will operate fine on a 9V battery, with the addition of a 7805 regulator to power the TTL logic used.
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