Marantz 5220 Manuel d'utilisateur télécharger pdf (Page 74)

I I7

VAC

Fig.

An

opto-

coupler controls

triac

gate

current.

1700

-Hz range.

Increasing

the

operating

frequency

is

eas-

ily

accomplished

by further

reducing

capacitance.

Reader's

Circuit.

Add

a dash

of imagination

and

chances

are you

can think

of

a

hatful

of

projects

for

the

light-

controlled

switch

shown in Fig.

3. Contributed

by

reader

Ted

Reiter

(1442

Brook

Dr.,

Titusville,

FL

32780), the

circuit utilizes

a number

of different

solid

-state

devices

-

ligh-

dependent

resistors

(LDR's),

a 555 IC timer,

an

op-

tocoupler

and

a power

triac.

When

activated

by external

light

sources

such

as a

flashlight

or the

sun,

the

circuit

can

be

used for

remote

control

applications

as an intruder

alarm

or

an automatic

light

or appliance

switch (hot

coffee

with the

rising

sun, perhaps

?).

The

555

serves as

a bistable

switch

controlled by

a pair

of

light

dependent

resistors,

LDR1 and

LDR2. When

the IC is

in its

high

state,

output terminal

3 is

connected

to the

dc

source,

but in the low

state,

pin 3 is grounded.

The

battery-

powered

control

circuit

is

effectively isolated

from

the

ac line

by

OC/.

In

operation,

light

striking

one of the

LDR's

will

switch

the

555

from

a high

to

a

low

state,

or

vice

versa.

If

high

initially,

light

striking

LDR1 causes

a positive

input

pulse

which

switches

the IC,

activating

OC/

which in

turn

supplies

a gate

signal to

the triac,

switching

this

device

on

and

applying

ac power

to the

external load.

If

the IC is low,

light

striking

LDR2

will

switch

the

device

to high,

de-

activating

OC/,

thus removing

the

triac's

gate

signal and

switching

off the load.

In

describing

his

circuit, Ted

did

not

specify the

type

numbers

of the LDR's

or triac installed

in his

original mod-

el, indicating

that

a

variety

of devices

can

be used.

Obvi-

ously

different

applications

require

varying

sensitivity,

while load

requirements

will vary

with

the nature

of

the

switched

device.

Depending

on the

nature

and intensity

of

the light

source,

either

CdS or

CdSe photocells

could

be

used

as

sensing

elements,

but identical

types

should be

used

for

both

LDR1 and

LDR2.

Ted

suggests

that

a stan-

dard

100

-V, 8 -A

triac is

more than

adequate

for

most

appli-

cations,

but it

should

be heat

-sinked

if

used near

its

maximum

ratings.

Resistors

R1

and

R2,

are used

to bal-

ance the

LDR

characteristics

but if

the LDR's

are

closely

matched,

the resistors

will

not be needed.

At

the

user's

option,

either a

6-

or

12 -volt

dc

source

can be used

with the

control

circuit.

Neither

lead

dress nor layout

is

critical and the

circuit

can

be assembled

on

pc

or

perf

board

or even on a small

chassis. Some

care is required in

placing and mechani-

cally mounting

the LDR's,

of

course, so

that

both are not

activated

simultaneously

by the light

source. Small tubes,

opaque shields, masks,

or

lenses

can be used, depending

on

the

specific

application.

Device/Product

News.

Responding to

the increasing

82

use

of microprocessors

and

memory

IC's,

the Vector

Elec-

tronic

Co., Inc.

(12460

Gladstone

Ave.,

Sylmar,

CA

91342)

has

developed

a new

DIP plugboard

designed

specifically

to

accommodate

those

devices.

The

board

accepts

two

supply voltages,

is

copper

clad

on both

sides for

shielding

and

to

supply primary

power

(positive

on one

side, nega-

tive

on the

other),

with interwoven

zig -zag

lines

(also

on

both

sides)

to facilitate

power distribution.

Designated

as

the

Mode14350,

the

board

will hold

6314-

or 16 -pin DIP's

or

five

24 -pin

microprocessors

and 45

DIP's.

The 4350

is

priced

at $14.95

each

in

unit quantities

and is

available

from

both local

and mail

order

outlets.

A lever-

actuated

solid

-state

switch

of

interest

to

ex-

perimenters

and hobbyists

is now

available

from

Optron,

Inc.

(1201

Tappen

Circle,

Carrollton,

TX 75006).

Identified

as the

type

OPS 100

Optical

Limit

Switch,

the device

does

not

use mechanical

switch

contacts. Instead,

the

lever

arm

operates

a

shutter

which

interrupts

a light

beam

between

a

GaAs infrared

LED

and

an npn phototransistor,

the latter

generating

an

output

signal (See

Fig.

4). It

can be

used

as

either

a normally

open

or normally

closed

spst

switch,

depending

on

a simple

mechanical

adjustment.

A

dc

source is

required

for

the

LED.

The

Fairchild

Camera

and

Instrument

Corp.

(464

Ellis

St.,

Mountain

View,

CA

94042)

has

announced

a 2048

-bit

static

n-

channel

RAM

ideally

suited

for

use

with

microproces-

sors.

The

new

product,

type

3539, is

organized

as 256

x 8

bits,

and is

available

in

two

versions

with maximum

access

times

of 650

and

500 ns.

Two

separate

chip -select

inputs

allow

direct

expansion

to

512 bytes

of

memory.

The

device

has

a power

dissipation

rating

of less

than

500

mW, re-

quires

a single

5 -volt power

supply.

It

comes in

a standard

22

-pin

DIP.

The

3539

also features

TTL-

compatible

inputs

and

outputs.

1

I

= I

L___-11-__1

Fig.

4. Optron

:s

OPS

100 optical limit

switch

provides

bon nceless

electronic

switching.

Fairchild's

East

Coast Imaging

Systems Division

(300

Robbins

Lane,

Syosset,

NY

11791) has

developed

a third

-

generation

charge

-coupled-

device

(CCD) television

cam-

era

offering

considerably

improved

resolution

over earlier

models.

The

Model

MV -201

has 244

-line resolution

and a

bandwidth

of 1.86 MHz.

It is

sensitive

to as little

as

0.000125

footcandle

of

illumination

at the

CCD elements.

The

cam-

era weighs

only 12

ounces

and

is

2" H

x

2.5"

W

x

3.75"

L.

Interfacing

directly

with

conventional

TV monitors,

the

MV -201

requires

only 4

watts

at

12 volts.

If you're

interested

in

the

design

and assembly

of

elec-

tronic

musical

instruments,

you'll find

it

worthwhile

to in-

vestigate

the

standard

IC's

offered

by

American

Microsys-

tems,

Inc.

(3800 Homestead

Road,

Santa

Clara, CA

95051).

Among

the interesting

devices

available

are the

S2555 and

S2556 top-

octave

synthesizers,

the

S2566 rhythm

generator

ROM, the

S8890 rhythm

generator,

the

S2567

resettable

rhythm

counter,

the

S2470 six -stage frequency

divider,

the

S50240

series

of top-

octave synthesizers,

and

the

S2193 seven -stage

frequency

divider.

Unit prices

range

from

$4.50

for the frequency

dividers

and S2567 resettable

rhythm

counter

to $22.50 for

the

S8890.

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