AEG Electrolux ERN 2922 User Manual download pdf (Page 43)

C19

0.01µF

R22<

50K:

R20

R21

From

33K

33K

IC

10

nn

Pin

24

018

0.014íF

o

o

9Vac

ARM

C20

10µF

DISARM

1A

o

C211_

0

1µF

RECT1

C22

T01µF

C26

2200µF

+5V

IC11

LM386

4

C23

T 10µF

IN

C27

0.1pF

IC12

7812

COM

OUT

R23

10

1

C24

0.1µF

C25

100pF

;(--

+12V

R24

1K

AA-

C29

47µF

C28

0

1µF

Speaker

8i2

LED2

POWER

oGND

Fig.

2. Audio

amplifier portion

of circuit is

shown

at top,

basic dc power supply

at bottom.

cuit in

Fig. 1.

When

/C/O is finished

generating

the

desired allophone,

its

output

at pin 8 goes

to a logic 1. This

output,

therefore,

indicates

to a

NAND gate

in ICS

that IC10 is ready

to be

triggered again.

This process

continues

until data output from

IC9

has reached

its

end.

When

the

vocal

warning

alarm

is

first

turned on,

the R1 /C2 network

sends

a positive

transient pulse,

which

finds its way

to the set input

at

pin

6 of the first flip

-flop in

IC6.

When

the pulse arrives,

the output

of

this flip -flop,

at pin 1, goes

high. Be-

cause this high

is fed

to an OR -gate

configuration made

up

of

NAND

gates inside

ICS,

the gate's

output

enables

the final NAND

gate in

the

IC to

send the pulses

that appear

at

pin

3 of ICS

to the inputs

at pin 1

of

IC8 and pin

20 of ICIO.

Since

the pin 1

output of IC6 is

at a

logic

1,

the same high logic

level is

delivered

to address input

A7 at pin

1

of IC9.

So the EPROM

sends

the da-

ta stored in

it starting

at address 128

to ICIO.

At this point,

you

will

hear

the first

message:

"I am a talking

alarm. You have

thirty

seconds

to

leave

the

car. Please hurry." When

this message

ends, IC9

sends

a logic 1

via

its

pin 16

output back

to IC6

which

resets

both flip -flops

and

causes

a logic 0

to appear

at the pin 1

output

of the first flip -flop.

Now

let

us suppose that

someone

attempts to open the door

of the pro-

tected premises (or move

your

pro-

tected

car,

if

that is

where

you in-

stalled

the alarm). The normally

open (No)

sensor

would

now

trigger

timer IC2,

whose

pin 3 output then

sends,

through a pair

of

inverters

in-

side IC7,

a positive transient pulse

to

the pin

8 set

input

of the second flip -

flop inside IC6.

This

causes the out-

put at pin 13

of

IC6

to go to logic 1,

enabling

the

final gate inside

ICS.

Because

the

standby output is nor-

mally

at

logic

1, pin

3 of

ICS

goes

high

and sends pin 1 of IC8

and pin

20

of

ICIO

high as

well.

This

causes a

logic

1 to appear

at

input

pin 23 of

IC9.

When

this occurs, the EPROM

sends the

data programmed into it

to

IC /0,

starting at address 256. Hence,

you

will now

hear the second

mess-

age:

"nine, eight, seven,

six,

five,

four,

three, two, one, zero."

From

the time this second

(count-

down) message

starts, you have 10

sec-

onds to

disarm the alarm

by setting Si

to DISARM (open

the

switch). Other-

wise,

the piezobuzzer will

sound.

You may

have noticed

that only two

of the

six

inverters

in IC7

are

being

used in

this circuit. The

sole purpose

of these two inverters

is to

transform

the 12

-volt pulses

generated

by the

timing

circuit into the

5 -volt pulses re-

quired

by the rest

of the circuitry.

As you

can see in Fig. 1,

this project

can accommodate

both normally

open

(No)

and normally

closed (Nc)

switch -type

alarm trip

sensors. If you

plan

on installing

the alarm inside

your home

or office,

you can use

either or

both types

of sensors, as the

need

arises. Door

and

window

sensors

should be

ordinary magnetic

-type

devices.

Use

glass breakage sensors

for

window panes

as

well.

If you

plan on installing

the alarm

in

your

car,

van

or

other

vehicle,

use

a normally

open

sensor to detect

mo-

tion should

someone attempt

to push

or tow

your vehicle.

As

shown in the lower

schematic in

Fig. 2,

this project uses

a convention-

al ac

-line- operated power

supply.

The power

transformer's

secondary

should

be

rated

to deliver

at least 9

Say You

Saw It In Modern

Electronics

February

1988 / MODERN ELECTRONICS

/

53

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