Music IC Alarm ICThe music IC module contains sound-generationICs and supporting components. It can play sev-eral musical tunes that are recorded in it. Its actu-al schematic is complex and looks like this:

This module has two different control inputs. TheOUT connection pulls current into the module (notout of it), usually from a speaker. This current isadjusted to make the music. Snap Circuits proj-ects 15 and 16 show how to connect this part andwhat it can do.

Its Snap Circuits connections are like this:

(+)

HLD

OUT(–)

TRG

Music for ~20 sec on power-up, then hold HLD to (+) power or touchTRG to (+) power to resume music.

Music IC:(+) - power from batteries(–) - power return to batteriesOUT - output connection

HLD - hold control inputTRG - trigger control input

The alarm IC module contains a sound-genera-tion IC and supporting components. It can makeseveral siren sounds. Its actual schematic lookslike this:

This module has three control inputs, and canmake five siren sounds. The OUT connectionpulls current into the module (not out of it), usual-ly from a speaker. This current is adjusted tomake the siren sounds. Snap Circuits project 17shows a simple way to connect this part, and proj-ects 113-117 show the connections needed tomake the five possible sounds.

Its Snap Circuits connections are like this:

Connect control inputs to (+) power to make five alarm sounds.

Alarm IC:IN1, IN2, IN3 - control inputs(–) - power return to batteriesOUT - output connection

IN1

(–)

IN2

IN3

OUT

Although Snap Circuits includes several parts thatare called integrated circuits, they are actuallymodules containing a number of parts. The mod-ules contain specialized sound-generation andamplifier ICs and other supporting components

(resistors, capacitors, and transistors) that arealways needed with them. This was done to sim-plify the connections you need to make to usethem.

More about the ICs in Snap Circuits

High Frequency IC

Space War IC Power Amplifier ICThe space war IC module contains sound-gener-ation ICs and supporting components. It canmake several siren sounds. Its actual schematiclooks like this:

This module has two control inputs that can bestepped through 8 sounds. The OUT connectionpulls current into the module (not out of it), usual-ly from a speaker. This current is adjusted tomake the space war sounds. Snap Circuits proj-ect 19 shows how to connect this part and what itcan do.

Its Snap Circuits connections are like this:

Connect each control input to (–) power to sequence through 8sounds.

Space War IC:(+) - power from batteries(–) - power return to batteries

OUT - output connection IN1, IN2 - control inputs

IN1

(+) OUT

IN2(–)

The power amplifier IC module (not inluded inmodel SC-100) contains an LM386 audio amplifi-er IC and supporting components. Its actualschematic looks like this:

This module amplifies a signal from its input. TheOUT connection will usually be directly to aspeaker. Amplifiers like this let a small amount ofelectricity control a much larger amount, such asusing a tiny signal from a radio antenna to controla speaker playing music. Snap Circuits projects242 and 293 show how to connect this part andwhat it can do.

Its Snap Circuits connections are like this:

Power Amplifier IC:(+) - power from batteries(–) - power return to batteriesFIL - filtered power from batteries

INP - input connectionOUT - output connection

INPFIL

(+)OUT

(–)

The high frequency IC (not in SC-100) is anTA7642 (or other equivalent) AM radio IC. It is aspecialized amplifier used only in high frequencyradio circuits. The circuitry looks like this:

Its Snap Circuits connections are like this:

This module converts an AM radio signal at itsinput into an audio signal at its output. SnapCircuits project 242 shows how to connect this partand what it can do.

INP INP(–)

OUT

High Frequency IC:

INP - input connection (2 points are same)OUT - output connection (–) power return to batteries

Recording IC

FM ModuleThe FM Module (not in SC-100 or SC-300) con-tains an integrated FM radio circuit. The insidelooks like this:

Its actual schematic looks like this:

This circuit is actually much more complex than itappears here, since it is built around an integratedradio circuit. A schematic of the circuitry within thispart would be too large to show here, but this blockdiagram gives a summary of it:

Its Snap Circuit’s connections are like this:

The antenna ( ) is a loose wire that should alwaysbe left unconnected and spread out for best radioreception.

Antenna (A1)

Antenna Symbol

(+)OUT(–)

FM Module:(+) - power from batteries(–) - power return to batteriesT - tune upR - resetOUT - output connection

or

The Recording IC (not in SC-100 or SC-300) is amodule containing a specialized recording integrat-ed circuit and supporting resistors and capacitorsthat are always needed with it. The inside lookslike this:

Note that the parts here are miniaturized and “sur-face-mounted” to the printed circuit board. Theactual recording IC is under the black blob of pro-tective plastic. Its actual schematic looks like this:

Its Snap Circuits connections are like this:

The recording IC can record and play back a mes-sage up to eight seconds long. There are alsothree pre-recorded songs.

Recording IC (U6)

Recording IC

(+)

OUT

(–)

Recording IC Module:(+) - power from batteries(–) - power return to batteriesRC - recordPlay - playOUT - output connectionMic + - microphone inputMic – - microphone inputRCPlay

Mic –

Mic +