Sound Effects Generator
The HT2884 IC can produce the following sounds which can be used in military models: 2 laser guns, 1 dual tone, 2 bombs, 2 machine guns and 1 rifle. Of these, the two gun sounds are most realistic. The laser gun and dual tone sounds could also be used as alarm sounds.
The HT2884 requires a power supply of between 2.2V to 5V DC and consumes just 1mA, making it efficient in battery powered models.
Control of the IC is via two inputs, Auto and Serial, as shown in the circuit diagram of figure 1. When connected to 0V, the Auto Input (pin 15) continually cycles through the available sounds and plays them without any pauses. With the Auto Input connected to +Vs, briefly connecting the Serial Input (pin 16) to 0V will play each sound in turn. It is not possible to select one sound and then play it once for each push of a switch.
Sound output can be to a piezoelectric sounder connected between pin 10 and 0V (A), or a normal speaker with a transistor amplifier (B).
The HT2884 also features five �chaser� outputs which are switched from low to high in turn when a sound is playing. There is also an End Output which briefly goes low when a sound stops playing.
The flash from a gun barrel can be achieved by connecting a 3mm or 5mm white LED to one of the �chaser� outputs of the HT2884, or through the use of a strobe tube. The former solution is the easier to implement since it does not require any additional electronics apart from a current-limiting resistor. White LEDs are now reasonably cheap to buy and they produce a intense white light with a slight blue tinge. Because the forward voltage of white LEDs is about 3.6V and they consume about 30mA, the resistor R for a supply voltage of 5V will be 47W.
Siren sounds
The UM3561 sound generator IC would be a good choice for models of emergency vehicles since it produces police car, fire engine, and ambulance siren sounds. It also provides a pulsating machine gun sound.
The circuit diagram is shown in figure 2. The UM3561 requires a power supply of 3V, and the sound it plays is governed by the settings of pins 1 and 6.HT2884 - Sound Effects Generator
Pin 1 + Pin 6 =Sound Played
No connection + No connection = Police siren
No connection + +Vs = Fire engine siren
No connection + 0V = Ambulance siren
+Vs + +Vs or 0V = Machine gun
