Memorex CP8 TURBO UNIVERSAL REMOTE CONTROL Manual de usuario descargar pdf (Pagina 56)

60

ELECTROLUMINESCENT

GLOW

STRIPS

Phosphor

displays

are interesting

and

can

produce

interesting

effects. This

lighted

display

background

may just

be the

thing you

need for your

next project.

TRANSPARENT

PLASTIC

SLEEVE

TRANSPARENT

INDIUM

OXIDE

CONDUCTING

ZONE

PHOSPHOR ZONE

REFLECTOR

ZONE

ALUMINUM

SHEET

='I1!

I

HIGH VOLTAGE

AC SUPPLY

Fig.

1 -The display is really

a sandwich

of substrates in a

plastic

case.

The

phosphor is the part that glows,

however.

By Stan Czarnik

DIN THE PRESENCE

OF A

SUITABLE ELECTRIC

CURRENT,

certain

chemical solids will

radiate light.

That is the principle

on

which

the light-

emitting diode

(LED) is based. The LED

has become

a

very

popular

electronic

component. A

much

less -familiar

example of such an

effect goes under

the name

of

electroluminescence.

Most LEDs

are built around single

crystal III -V

corn -

pounds, such

as gallium arsenide,

and require

fairly high

levels of

direct current and low levels

of

voltage.

Most elec-

troluminescent

devices involve

microcrystalline

powder

phosphors

based on

II -VI compounds,

like zinc sulfide,

and

require fairly low

levels of

current and high levels

of

voltage,

alternating or direct depending

on construction.

Electroluminescent

Design

Most

LEDs produce

a single,

concentrated,

point

of il-

lumination.

Most electroluminescent

components

are made

to produce

a relatively

soft, diffuse,

surface of light.

That

makes

the electroluminescent

panel

especially

appropriate

for display,

decoration,

and

unusual lighting

effects. With

a

little imagination,

you

are sure

to find

many interesting

applications

for them

in your next

project.

The typical

electroluminescent

plastic panel

consists of

four

internal layers.

First,

there is the

electroluminescent

phosphor

itself. That

is usually purified

zinc sulfide

activated

with

copper.

The phosphor

is embedded

in

a dielectric medi-

An electroluminescent

panel made with

zinc sulfide

emits a

cool, gentle, green glow.

It can be used as

a background for

any

display, provided

you

can

give it the voltage

it requires.

um and sandwiched

between two flat,

parallel electrodes.

One of

those is made of transparent indium

oxide. The

other,

opaque electrode is

usually thin aluminum

foil. In many AC

panels,

a reflective layer

of barium titanate is

placed between

the phosphor

and the aluminum.

That serves

to reduce elec-

trical

breakdown and

direct most of

the light created within

the panel through

the transparent

electrode. Finally,

leads are

attached

to the electrodes,

and the

entire cell is enclosed in

a

clear plastic

sleeve (see Fig.

1).

Note how

similar that is

to the structure

of a simple

capacitor, i.e.,

a dielectric

between two conductive

plates. In

fact, when

electroluminescent

panels first

became commer-

cially available

around 1950,

they

were

known

as luminous

capacitors

and condensor

lamps.

The

Glow

Strip

A small

electroluminescent

plastic glow

strip, including

a

high -voltage

power

inverter,

is currently

available from

the

All- Electronics

Corporation, 15004

Oxnard

Street,

Van

Nuys,

California

91411. It's

easy to operate,

attractive, inex-

pensive, and a lot

of fun besides.

One glow

strip (catalog

number

GS -400) will

cost you $6.50

(two for

$12.00) plus

$3.00 for shipping

and handling.

The

minimum order

is

$10.00.

When

your glow

strip arrives,

examine it

carefully, with

a

magnifying

lens perhaps,

near

the edge and

near the

two

wire

Here's

an electroluminescent

glow

strip and

voltage inverter

from

All-

Electronics

Corporation. Be

careful with

the inverter

when

connected to the

battery,

as the

output

is

high voltage.

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