Epson L90P - TM Two-color Thermal Line Printer Manual de usuario descargar pdf (Pagina 69)

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Electronic

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Control

TAKE

NIGHTTIME NATURE

PHOTOS

ELECTRONICS

has always

been an

im-

portant factor in

the development of

new

hobbies

and

the improvement of

old

ones. Photography,

in particular has

benefited

tremendously through the use

of electronic

devices that

make

photo-

graphic equipment and techniques more

accurate,

more flexible,

and easier

to

use

under adverse conditions. As an exam-

ple,

with the aid

of

a

few relays

and a

solenoid, you can build an

"Electronic

Shutter

Control," that will enable you to

get

into

the

fascinating field of night-

time

nature photography.

The Shutter Control operates on the

electric -eye

principle; the

subject to be

photographed breaks an almost invisible

beam

of

light

to a photo -cell,

triggering

the

shutter and

taking his

own

picture.

Once

the system

is

tripped,

a signal light

that can be

seen from hundreds

of

feet

away goes

on

and a

relay

simultaneously

shuts

down

power

to the system. The

power disconnect

feature is

a

real

battery

BY WALTER

B.

FORD

saver -especially if you plan to

leave

the

system unattended overnight.

How

It

Works. Power is applied to

the

Electronic

Shutter Control circuit

through J1

and J2

in Fig. 1. With both

S1

and

S2

closed, the

beam

from

control

light I1 is

directed

at

PC1, causing

the

resistance

of

the

photocell to

reduce

enough to allow

K1

to be energized. When

K1 picks

up, its normally closed contacts

open, depriving

K2

and subsequent cir-

cuits of power.

Now,

when the control

light beam

to

PC1 is interrupted, K1 is de- energized

and

power

is

applied to

K2.

This

results

in

three

simultaneous operations : K2 is

latched in through its

lower

contacts;

a

pulse

is

applied to shutter solenoid

L2;

and

power is delivered

to

the heater

of

thermal

relay K3

through the upper

con-

tacts of

K2. After

a short

interval,

the

contacts

of relay K3

close to complete

the circuit through

the solenoid

of K4.

April, 1969

75

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