Elenco Electronics MO-1251 Manual de usuario descargar pdf (Pagina 44)

100

R19,

20K;

ANT

5pF

iF1

C1 Q1

002

MPSH11

-----t-

10K

24pF

4751

.002

R16

R15

13061

6.8K

I C6

18pF

r--1

- C12

.47

C13

100p ir

LEDI

818

10K

R20

C15

1µF

C7 85

039 41K

10FF

N+

470K

r -v^-

TP1

R10

56K

ICI

-a

LM358

.01

q GND

¡-jFB2

6.2K

IC1-b

LM358

R12

47K

-1N 1N

1/y

R14

813

100K

10 MEG

33K

T-T`806b

R21

10K

R17

15K

.---

C16

C14

10µF

{

--a-44

TP2

R11

10K

IC3

7555

822

100K

C18

50µH

.01

IC4

78L05

C17

10µF

+6-16VDC

GND

FIG.

5-THE RF

RECEIVER /ALERT

BEEPER sounds a warning buzzer when it receives

the RF

signal.

R4/

R57

--v-

ICI

-C1-

8,2

-ILED2

IR-LEDI

+ C2

FIG. 6 -PARTS PLACEMENT

for the IR

transmitter.

receiver /beeper

The RF receiver /alert beeper is

shown in Fig.

5; the

receiver

circuit

superregenerative receiver. An

am-

plitude- modulated RF carrier is cou-

pled from the antenna, through CI,

into T1, and then to QI's base. Re-

sistors RI -R4 bias

for an emitter

current of approximately

I mA.

Ca-

pacitor C5 bypasses

the RF signal,

but not audio signals, to ground. The

value of

C2 is

selected

to cause

self -

oscillation, or

motorboating,

which is

requirement

superregenerative

detector. In that

configuration, Ql os-

cillates

at an

frequency of 49.890

MHz, at

repetition

rate of approxi-

mately 450

kHz. During

each

450

kHz

cycle, just before

Ql breaks into

RF oscillation,

the

circuit

functions

as a

very-

high -gain

RF amplifier.

Transistor Ql's

average DC emitter

current increases

and decreases ac-

cording to the amplitude of the

signal. Because

the RF signal is am-

plitude-

modulated by a 490 -Hz

tone,

490

-Hz

voltage

appears

the

junc-

tion of Ql's collector

and

R4.

C7 cou-

ples the 490 -Hz signal from

the

receiver

op -amp

ICI -a,

which

pro-

vides

10 -dB gain. ICI -b further am-

plifies

and clips the

signal, shaping

into square

pulses. Resistors R7 -R9,

R12, and RI3 allow

ICI to

powered

by a single

-ended power supply.

The square-wave

pulses from ICI -b

are fed

to tone -decoder IC2 through

R15

and CIO. The decoder's

input

signal

voltage

is reduced by R16,

PARTS

LIST

RECEIVER/

RF TRANSMITTER

All resistors

are 1/4-watt,

5 %, un-

less

otherwise noted.

R1, R5,

R7, R17, R18

-1 megohm

R2-

200,000

ohms

R3, R6,

R10- 100,000

ohms

R4 -2700

ohms

R9, R13- 10,000

ohms

R8, R19-

R21 -10 megohms

R11-

20,000

ohms, trimmer

R12-

53,600

ohms, /

-watt,

R14 -6200

ohms

R15

-3300 ohms

R16 -470

ohms

All

capacitors

are

rated for

least

16 volts.

C1-0.1 µF, metalized

film

C2, C14

-0.01

p.F, metalized

film

C3, C7, C8,

C11, C16 -0.001

iLF, ce-

ramic

disc

C4, C12,

C13, C17

-10

p.F, elec-

trolytic

C5-200 pF, ceramic

disc

C6-0.022 p.F, metalized

film

C9-27

pF,

ceramic disc

C10

-180 pF,

ceramic disc

C15

-100 µF, electrolytic

Semiconductors

IC1 -LM358

op -amp

IC2, IC3

-7555 CMOS timer

Q1-

VT1314 Vactec

NPN infrared

phototransistor

02, Q3-

2N4403 PNP

transistor

04, Q6 -BS170 MOS

power tran-

sistor

05-

MPSH11

NPN transistor

-1N914

switching diode

LDR1,

LDR2 -VT -835

Vactec

photo-

conductive cell

Other components

ANT -1 -meter

whip,

or a 1 -meter

length

No.

hookup

wire

L1-

0,47

-µH

RF inductor (TOKO

7KM

series)

L2-

0,6 -11H

antenna

coil

(Time

Space

Scientific

TS500-

34 -24)

L3-

L5 -50

-0H

miniature

choke

T1 -RF

transformer

(Time

Space

Scientific TS2343

-18 -5)

XTAL1- 49.890

-MHz

series -reso-

nant

crystal

Miscellaneous:

SPST

switch

(op-

tional), PC

board, IC

sockets, etc.

Note: The

following items

are

available from

the source men-

tioned in the Sources Box.

and L1 -L5 (kit TR3

-1),

$10.95;

board (TS3.3), $9.95; LDR1,

LDR2, and

(kit

TR3 -3), $9.95;

XTAL1 (49.890

MHz), $5.35; All

components including

semicon-

ductors, resistors,

capacitors,

dip sockets,

and a

board (kit

TR3 -4), $45.95.

(None of the kits

include

an antenna, switch,

enclosure.)

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Elenco Electronics MO-1251 Manual de usuario Pagina 44

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