R6 and R7, C6 and C7 are two resistors and two capacitors, respec-
tively, that form a filter (a low passfilter) that eliminates high-frequency
noise prior to the signal reaching the amplifier.
C8is a capacitor that removes any DC offset from the output of IC1.R8is a potentiometer that controls the sound volume.
IC3,an LM386N-1 audio amplifier, takes the electrical signal generated
by the SpeakJet when you push and release one of the switches in the
puppet and then amplifies the electrical signal to create enough power
to drive the speaker.C9is a capacitor that improves the stability of the LM386 amplifier to
prevent problems such as oscillation.
Capacitor C10 acts as a current bank for the output. This capacitor
drains when sudden surges of current occur and refills with electrons
when the demand for current is low.C11is a capacitor that removes any DC offset from the output of the
LM386 amplifier.Building Alert: Construction Issues ...........................................................
The tactile switches that we use in this project have very tiny leads that are
meant to be surface mounted in an assembly line. Given that we (and you)
don’t have an assembly line handy, we used needlenose pliers to crimp wire
around the tiny leads to hold the wires in place while we soldered them.The DB9 connector has a small metal tube or cup to which you can solder
each wire connection. We found that the easiest way to solder a wire to one
of these tubes is to melt some solder into the tube, reheat the tube, and then
insert the bare wire end into the melted solder.When inserting electrolytic or tantalum capacitors into the breadboard,
pay attention to the polarity. Inserting the capacitors the wrong way could
damage the capacitors and possibly other components in your circuit. The
longer lead of the capacitor is the + side. The schematic shows you which
direction to insert the capacitor. For example, the + lead of capacitor C2 goes
toward Pin 1 of IC2, and the other lead goes toward Pin 3 of IC2.In order to feed wires from the tactile switches to a location where they could
be connected to the electronics box by the shortest path, we had to cut a few
holes in the fabric of the puppet. Don’t worry; he won’t feel a thing.Chapter 7: Murmuring Merlin 143