Radio Shack SSM-1750 User Manual download pdf (Page 76)

Two

Band

Stereo

LED

Power

Meter

(from

page

42)

F' g. S.

Actual -size alignment

template

for

LED installation.

the

bottom

of the

board.

Then pre-

pare

a

two -conductor

zip cord

by

re-

moving

'A

" of

insulation

from

the

conductors

at

both

ends.

Tightly

twist

together

the

wires in each

con-

ductor

and tin

with solder.

Make

these

cords

as

long as

needed

to

route

between

your

amplifier

and

the

Power

Meter

after

final

installation

in your

vehicle. Solder

one

end

of

this

cable

to

the pads

labeled

LEFT

IN-

PUT and

RIGHT

INPUT

from

the

bot-

tom

side

of

the board.

Next,

connect

the

red +

12 -volt

and

black

ground

power

leads to

the

pads

labeled

+

12V and

GND

on

the

bottom

right

side

of the

board.

Make

these

leads

long enough

to

reach

the

vehicle electrical

system's

ground

and

any

point

that

is at

+

12

volts

when

the

ignition

is on

and

is off

12V

power

supply

Fuse

POWER

LINES

Audio

generator

I]

Power

meter

Fig.

6.

Test setup

for

calibration.

when the

ignition

is off.

The

+

12 -volt

wire should

have

an in -line

fuse

holder in

it. Install

a 1- ampere

fast

-blow

fuse in the

holder.

Any enclosure

large enough

to ac-

commodate

the

circuit

board

and

that

has one panel

that can

be

re-

placed

with a clear

or

tinted panel

can be

used to

house the project.

An

ideal size

would have

internal

dimen-

sions

of 7

VI " x

2'/ "

x 111 ".

You

can

make such

an

enclosure

from

" -thick

Plexiglass or

'/a

" -thick ply-

wood, or

you can

modify

an existing

plastic or

metal chassis

to

suit your

needs.

Just

be sure to

make one

7'/a "

x 2'/

" panel

from bronze

or

neu-

tral -gray

tinted transparent

plastic

to

provide good

contrast

in

relatively

bright

light

for easy

viewing

of the

display.

Whichever

material

you

use,

paint all

inside surfaces

of the

enclo-

sure,

except

the

faceplate,

flat black

to

cut down

on

reflections.

Mask from

view

the left and

right

portions

of

the circuit

board

not in

the

LED matrix

area.

This can

easily

be done

by

applying

black electrical

tape

or black

paint

to

the appro-

priate areas

on the

inside

surface

of

the

faceplate.

Mount

the circuit

board

inside the

enclosure

with

four

sets of

'1

"

spacers

and

4 -40

x 3/4

" machine

screws,

nuts and

lockwashers

to

the

faceplate.

The

lockwashers

between

the

nuts

and circuit

board

are

impor-

tant

because

they prevent

the

hard-

ware from

working

loose due

to

vi-

bration

from the

road.

Because

the

display

consists

of

LEDs

whose different

colors

are self

-

explanatory,

there

is

no need

to

label

the

faceplate.

However,

if you

wish

to give

your

project

a more

profes-

sional

appearance,

you

can

apply

legends

to

the outside

surface

of the

faceplate.

Typical

legends

include

LEFT

LOW

FREQUENCY,

RIGHT

LOW

FREQUENCY,

LEFT

HIGH

FREQUENCY

and

RIGHT

HIGH

FREQUENCY

to

the

left of the

individual

bargraphs

in the

blanked

-out

areas.

Under

the bot-

tom

bargraph,

you

can bracket

each

color

grouping

and

letter

LOW

POWER,

MEDIUM

POWER

and

HIGH

POWER

legends

in

the

appropriate

areas

and

then

run

vertical

lines to

separate

the color

groups.

All

lettering should

be

done

with

a

white

dry- transfer

lettering

kit ap-

plied directly

to the

front

surface of

the

faceplate.

Since this

type

of

let-

tering

is

very fragile,

you

should

place an

additional

% " thickness

of

clear

Plexiglass

over

the entire

face-

plate to protect

the

lettering.

In

this

event,

use

1 " -long

screws

for mount-

ing the

board.

Checkout

and Calibration

Referring

to

Fig. 6, connect

the

Power

Meter's dc power

leads

to a

12 -volt

dc source.

The first column

of LEDs

at the

left (farthest

from the

transistors)

should

immediately

light,

indicating that

power

has been

applied

to

the project.

All other

LEDs

in the display

should

be off.

Apply an

input signal

from an

audio

signal

generator

or other

audio

source between

the

LEFT

INPUT chan-

nel

lead and

the negative

power

-sup-

ply lead.

Turn up the

sound

until the

LEDs

in the top

and /or third

row of

the

display begin

to

light.

The row(s)

of

LEDs that

turn on

will

depend

on

the

frequency

or

frequencies

deliv-

ered

to the

Power

Meter's

input.

If you

are using

an

audio

signal

generator,

sweep

the

frequency

con-

trol

from the

low to

the high

end

of

the

audio

spectrum

while observing

the

LED display.

The

LEDs

in the

top and

third

rows

come

on

at fre-

quencies

above

and

below

about

3

kHz,

respectively.

90

/

MODERN

ELECTRONICS

/

September

1986

Say

You Saw

It In

Modern Electronics

1 2 ... 71 72 73 74 75 76 77 78 79 80 81 82 83 84

Comments to this Manuals

No comments