Download Constructional Project

Constructional Project
(Left): this view shows the
business end of the Galactic
Voice with a small speaker
glued inside the ‘grille’.
The ‘case’ is a speaker
tuning port, which just
happens to be the
right size!
(Right): here’s
the opposite end.
The microphone
is located inside
the grommet (top)
while the three
controls are Effect,
Depth and Volume.
The LED shows that
power is switched on.
The pots must be earthed to the 0V
rail on the PC board with a linking
wire from the 0V PC stake soldered
to each pot body.
The coating on the pot does not take
solder easily – almost certainly, you
will need to scrape it away where it
is to be soldered to ensure a good attachment for the wire.
Fig.5 shows the holes and sizes
for the control panel and the speaker
‘grille’ discs. These are made from
1mm aluminium sheet offcuts. Cut
out the circle shapes with tinsnips or
a hacksaw and file to shape. The front
(62mm) disc requires a series of holes,
as shown, to allow the sound to escape
from the loudspeaker.
We painted the outside face of our
grille black using a spray can. When
the paint was dry, the loudspeaker was
secured to the grille with a smear of silicone sealant around the speaker rim.
Wire up the loudspeaker using a
170mm length of mini figure-8 speaker
wire and secure it around the magnet
on the loudspeaker with a cable tie.
This will ensure a tug on the wires
doesn’t break off the lugs on the
loudspeaker.
Attach the speaker grille and loudspeaker assembly to the inside of the
flared end of the port using silicone
sealant.
The hardware
The PC support board requires cutouts to allow the M4 nut to be soldered
to the board and also a notch to allow
the matching M4 screw to insert into,
and through, the nut. These cutouts
are the non-copper areas shown on the
PC board. They can be cut out with a
drill and hacksaw and finished with
a fine file.
Solder a brass M4 nut to the top
edge of the support PC board as shown.
When you solder the nut onto the PC
board make sure the inside thread is
not soldered.
62 DIAMETER
9
B
58 DIAMETER
A
A
19
A
19
10
C
34
D
10
Fig.5a
CONTROL PANEL
Next, we need to attach the control
panel label (Fig. 6) to the control panel
disc and cut the holes out through the
panel with a sharp knife.
Place the power switch, the LED
bezel and LED in position and insert
the rubber grommet in the microphone hole.
Wire the microphone, using shielded audio/mic. cable and then insert
the microphone into the rear of the
grommet.
Attach the control panel to the PC
board and secure it using the potentiometer nuts. Solder the microphone
lead to the top side of the PC board (PC
stakes) and the LED and switch direct
to the appropriate copper pads on the
underside of the PC board.
The 9V battery holder is mounted on
15mm-long standoffs and M3 screws,
as shown in Fig.4. The three mounting
holes in the battery holder are drilled out
to 3mm (or 1/8in.) and counter-bored to
suit the M3 countersunk screws.
CL
Everyday Practical Electronics, July 2008
HOLE DIAMETERS:
A: 7.0
B: 12.0
C: 6.0
D: 6.5
E: 5.0
ALL DIMENSIONS
IN MILLMETRES
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
Fig.5: the drilling
detail for the front
(control) panel
(Fig.5a, left) and
the rear (speaker
baffle) panel
(Fig.5b, right).
Note that these
1mm aluminium
discs are different
sizes.
Fig.5b
LOUDSPEAKER
GRILLE
49