Memorex CP8 TURBO UNIVERSAL REMOTE CONTROL Instrukcja Użytkownika Pobierz pdf (Strona 40)

44

All the fun and

excitement that

Reno,

Las Vegas, or Atlantic

City have to offer

without fore

-going the

comforts of home

BUILD

THE ELECTRONIC

BANDIT

By

Daniel

P.

Ray

ANYONE WHO HAS EVER

PLAYED A SLOT MACHINE,

more

affectionately known

as a one -armed bandit, is

familiar with

the excitement

of trying to hit that

elu-

sive

"jackpot."

Unfortunately,

they also know how

expensive

it is

to play, since the

odds of

winning

aren't

all that great.

But take heart!

With a little

electronic prestidigitation,

you

can put

together the Electronic. Bandit

-an

electronic

slot

machine

that provides

all the thrills of

the real thing

at a

fraction of the

cost.

How It

Works

Figure

I shows

the Electronic Bandit's schematic

diagram.

As shown,

each of three vertical

rows of LEDs

is triggered by

a similar

circuit. In

the first row, UI (the

first of three 555

oscillator /timers)

is wired

to create

a

stream

of pulses,

the

frequency of which

is determined

by RI and

CI. Pressing S2

triggers

the pulses, and

at the

same

time

causes C4 to charge

The author's

prototype of the Electronic Bandit

is shown here,

prior

to being placed in its

enclosure.

Note

the bending

of

the

pins

to allow

surface

mounting.

through

a

voltage-

divider

network, consisting

of resistors R3

and R4.

When

S2 is released,

UI continues to oscillate

(outputting

a

stream

of

pulses) until

C4 has discharged through

R4,

.

pulling pin 4

of UI low, thereby

resetting the oscillator.

The

output of

U I is fed through R5

to the clock input of

U2 (a

4017

decade counter /divider).

The counter

is

wired

to count

until

the last of five LEDs lights,

at

which

time it recycles. The

result is that

when

S2 is momentarily

pressed, the

LEDs

glow

in sequence,

creating

a "rolling"

effect. Finally the rolling

effect stops,

leaving one

random LED lit.

Resistor

R6 keeps

the input of U2 from

floating after

UI

stops

sending pulses.

That operation

is the same

for the other

two rows of LEDs

except that row two stops

rolling after row

orr,

and row three stops rolling

after row two, because of

the

values

of

C4, C5, and

C6.

The

three diodes DI,

D2, and D3

are

necessary to keep

C4, C5, and

C6

isolated

from each

otter.

An interesting

feature

of the circuit

is that the 4017B

counter can be

programmed

to count to any

number between

two and ten, thereby

allowing the

builder to change

the

odds

by

adding or subtracting

LEDs

from each vertical

row. (See

Table

I for details.)

The circuit shown

contains five

LEDs

per

row and makes

for a nice,

compact, handheld

project

that's

lots of

fun to build

and use.

Assembly

The author's prototype

of the Electronic

Bandit

(sse pho-

tos) was

built on

a printed- circuit

board and

the

whole

thing

was

enclosed in

a 5

%H,

x

2%

x

I%-inch

project

box (Radio

Shack

part #270-233).

But instead of

drilling

componenting-

mounting

holes in

the printed -circuit board,

the author

chose

to use the PC board

as a cover,

with

the components surface

mounted on

the copper -trace side.

Once you've obtained

all of

the components,

including the

enclosure specified in

the Parts List, the

next thing to do is

to

cut a copper -clad

PC board to fit in place

of the cover. When

that's

done, the next

task is to etch the

circuit board. Figure

2

shows

the PC

-board etching pattern

used by the

author in the

proauction

of his prototype.

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