Memorex CP8 TURBO UNIVERSAL REMOTE CONTROL Manuel d'utilisateur télécharger pdf (Page 85)

100

potential is applied to the anode of DI,

forward

biasing that unit and causing it

to conduct.

While

that action

is going on

the

upper terminal, a

similar (but opposite)

event is taking place at the negative

terminal.

negative

on the lower termi-

nal reverse biases D4 so there is no

current flow through that unit.

the

same

time

D3 is forward biased, plac-

ing a low on the negative terminal of the

meter,

which

indicates the

voltage level.

By analyzing the current flow

with

the input polarity

reversed, you'll dis-

cover that while the input polarity has

reversed itself, the

potentials on the

meter have not. It's obvious that the

circuit

won't

tell you the polarity of

the

applied

voltage, but it

does

give its

magnitude.

Utility Audio

Amplifier

'Mc next circuit to roar down the pike

is the utility audio amplifier

shown in

Fig. 3. The basic amplifier offers a

volt-

age gain of about 200

with

a .4

-watt

output. If you chose to build that

handy

PARTS

LIST FOR

THE

UTILITY

AUDIO

AMPLIFIER

Cl, C2,

C7- 0.1

-1,F,

100

-WVDC

My-

lar

capacitor

C3, C5, C6 -100- µF,16

-WVDC

elec-

trolytic capacitor

C4-

-1.1F,

-WVDC,

-WVDC

electrolytic capacitor

J1-

Headphone

jack

R1- 1000

-ohm

1/2-watt, 5% resistor

R2- 10,000 -ohm,

potentiometer

-10

-ohm

1/2-watt, 5%

resistor

SPKR1-4 ohm speaker,

3- -o -4

-inch

diameter

-LM386

low- voltage audio power

amplifier

Perfboard

materials,

socket,

9 -volt

battery, wire, solder,

hardware, etc.

0.1

bench amplifier,

will

never sit

idle for

long. It's

just too convenient to use

testing a new project or troubleshooting

a piece of equipment.

The utility amplifier

is designed

around the popular

LM386

low- voltage

audio power amplifier,

which can

ordered

from a number of

mail order

houses, or purchased

from

local elec-

tronic parts house.

The amplifier circuit

can

be built on a small

section of perf-

board and housed

a plastic

or metal

cabinet that's large

enough to accom-

modate a 3- or

4 -inch speaker and a

battery.

Use an IC socket for U I and

keep

all

interconnecting component

leads as

short as

possible.

As in most amplifier

circuits, a

sloppy wiring job can turn a

prince of a project into a croaking

frog.

Utility

Amp Add -ons

Me usefulness of the utility audio

amp can be expanded by

building the

three input circuits shown in Fig.

4. The

simple two -component

circuit in Fig.

4A turns

the amplifier

into an RF AM

detector. Most any RF

with AM modu-

lation riding along can be demodulated

and heard on the amplifier's

speaker.

The circuit

in Fig. 4B

turns

the ampli-

fier into

an emergency

BC AM receiver

that should pickup at least one local

radio

station. Throw ten

feet of wire out

the

window and connect it to the top of

LI and screw the coil's slug in or out for

the strongest signal.

Figure 4C is nothing more than a

hand

-wound

inductive pickup coil that

can be

used to

seek out inductive trans-

mitted interference,

including 60 and

120 Hz. Also the coil can serve as an

inductive telephone pickup or as a re-

ceiver to pickup inductive transmitted

audio.

HEADPHONE

JACK

SPKR1

452,

3- SPEAKER

Fig.

3- Designed around

the

popular

LM386 low- voltage

audio power

amplifier.

this utility

audio amplifier can save

loads

time when building or trouble-

shooting some pet project or prized

electronic

instrument.

TEST

PROBS

39pF

IN34A

OLD B.C.

LOOPSTICK

ANT.

COIL

WIRE

LEAD

ANT.

IN34A

005

FIG.3

200 TO 300 TURNS

=28

WIRE

WOUND

1'4 -INCH

3 -INCH

FERRITE

ROD

FIG. 3

FIG.

Fig. 4 -By adding one of these sub -

circuits to the utility amp, you can

make that

somewhat

hum -drum circuit

perform some

really

useful

tasks. The

circuit

add -on in A turns the amplifier

into

RF AM

detector;

B turns the

amplifier into an emergency BC

receiver, and C is nothing more than a

hand wound inductive

pickup coil

that

can be used in conjunction with the

utility amplifier to seek out inductive

transmitted interference, or serve as

an inductive telephone pickup.

PARTS

LIST FOR THE

UTILITY AMP ADD -ONS

-39

-pF ceramic disc

capacitor

C2- 100

-pF ceramic disc capacitor

C3- 0.005 -pF

Mylar

capacitor

Di. D2 -IN34A

general

-purpose

germanium diode

L1 -See text

L2- 200 -300 turns

#28

wire

','c-

inch

3 -inch

ferrite rod

Printed

circuit or

perfboard materials,

enclosure,

sockets, wire,

solder,

hardware,

etc.

Current

Limiter

Murphy

lurks

in your

workshop

and

shows

up periodically

to destroy

your special

semiconductor devices in

the safest of experiments, then

the

cir-

cuit in Fig. 5 might just send Murphy a

message and

save

the day.

That single -

transistor

circuit places an

electronic lid

on the maximum current

that can pass

through it. By placing the current

limit-

ing circuit in series

with

your delicate

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Memorex CP8 TURBO UNIVERSAL REMOTE CONTROL Manuel d'utilisateur Page 85

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