Epson L90P - TM Two-color Thermal Line Printer Manual de usuario descargar pdf (Pagina 52)

BY L.

STRIGGOW

CONTROL

UP TO

200 WATTS WITH

A FINGERTIP

ELECTRONICS

experimenters

are al-

ways looking

for

new ways

to con-

trol

the

light

fixtures

their homes.

Here's

the

latest

wrinkle

-a light

switch

that turns on

and

off

with

just

touch.

You may

have

seen

this

type

of switch

the call

buttons

on some new

elevator

controls. It

doesn't

provide

any dimming

control,

but the

convenience

of being

able

to turn the lights

on or

off

with the

touch of

finger,

or elbow if your

hands

are full, is

real

plus.

Construction.

The

circuit for

the

touch

control is

shown in

Fig. 1. Although

any

type

construction

can be used,

the

author built his

on a small PC

board

whose foil pattern

is shown

actual -size in

Fig.

2. Note that, instead

etching

away

copper

to produce

a network of intercon-

necting

leads,

in this case you only

etch

away

relatively

thin isolation lines

be-

tween the

copper segments.

Once the

board is made,

assemble

the components

shown

in Fig.

this assembly,

the SCR's and

ca-

pacitors

are inserted conventionally

while

the resistors

and

diodes are mounted

vertically.

To install

the two

transistors

and the

silicon unilateral

switch,

bend

the leads over

and mount

the units

up-

side

down on the board.

Use fine

solder

and a

low-

wattage soldering iron.

Make

sure that there

are no solder

bridges

across

the isolation

lines on

the board.

Caution. Because

full line

voltage is

present

at various points in

the

circuit,

once the PC

board has been

built and

checked and

connections have been

made

it,

is suggested

that the

entire as-

sembly be encapsulated

using

any com-

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