Elenco Electronics MO-1251 Uživatelský manuál stáhnout pdf (Strana 23)

HARDWARE

HACKER

Refilling SX toner

cartridges

BOY, THERE SURE HAS BEEN

A LOT OF

helpline response

to the solid

-

state compass stuff we looked

at

two

months

ago. I guess I

did men-

tion that

you can get fluxgate sen-

sors off

the

shelf

from Radio

Shack. Meanwhile,

the original

"horse's mouth"

paper

about all

that is Earth's Field Magnetometry

by

W.F.

Stuart,

appearing

in

Reports

on

Progress

in Physics,

1972,

vol.

35, pages

803-881. And

you may also find RecentAdvances

in Fluxgate

Magnetometry

from

the

IEEE

Transactions

on Magnet-

ics, MAG

-8,

no.

1, pages 76-82

of

more than passing interest.

One helpline

caller

has

asked

why magnetoresistive

sensors

couldn't

be used. Those

are pri-

marily to

be used with very strong

magnetic fields,

and I

don't

think

they

are

nearly

sensitive

enough

for

any compass

use.

Far

and away

the

most

off

-the

-wall winning

en-

try

in

our fluxgate compass

con-

test

came

from

Dr. Dennis

O'Leary

who

studies fish whose

ears

have

built -in magnets.

See his paper

on

"Magnets in guitarfish

vestibular

receptors ",

over

in

Experientia, v.

37 (1981), pages

86 and

87.

Several

callers did give me

some

additional input in infrared

filters.

Apparently,

unexposed 35 -mm

photo film works

just fine. Years

ago,

I had

a student learn

that the

hard way.

He built a shaft

encoder

having the light

transmission pat-

tern

exposed on

a

litho film

disk.

The trouble

was that the infrared

light whipped

on through the

black parts just

as easily as it went

through the

clear portions.

Some infrared response

curves

on their various

plastics is

avail-

Refilling SX cartridges

More

digital

sinewaves

Minimum order

hassles

Micropower regulators

Mass teleportation card

DON

LANCASTER

1

to 65,536

digital

input word

D/A

converter

1414

256 s ep sine

lookup

table

sinewave

output

eight

most

significant

bits

24 stage

16.777216

Mhz

adder/accumulator

'

reference

clock.

FIG. 1-DIGITAL SINE

WAVES generated

by phase addition.

The input

word sets

how fast

the

waveform phase will advance,

in turn deciding

the directly synthesized

output

fre-

quency. The values shown

will generate

1 Hz to 65.536

kHz in 1 -Hz steps.

able

in

a "PEL

-ette" known as "In-

frared Transmittance

of Plexiglas

Colors that are Opaque

in the

Visi-

ble

Portion of the Spectrum,"

available

from

the

folks at Rohm

and

Haas.

Every once

in

a

while a resource

comes

along

which is

absolutely

and unquestionably

in that "must

have" category.

That is

certainly

true of the Signal

from the

Whole

Earth Review people.

That is

a

mas-

ter directory of

virtually

all

com-

munications resources,

well

done

up

in the style of the original

NEED HELP?

Phone or

write

your

Hardware

Hacker

questions directly

to:

Don Lancaster

Synergetics

Box 809

Thatcher, AZ

85552

(602)

428 -4073

Whole Earth

Catalog and

costing

$16.95. No hacker

can

ignore that

book.

It is

far too

important.

As per usual,

this

is your column

and you

can get technical

help and

off

-the

-wall

networking

per the

Need

Help box.

As

is

customary,

many of

the products

and

services

mentioned

do appear

in the

Names and

Numbers

sidebar.

Let's start off

with a

loose end...

Digital sine

waves

There was a

surprising amount

of

interest

in

our

recent digital

sine

wave stuff, and

I apparently

did

forget to

include one

key tech-

nique.

Thanks to

Tim Green,

an-

other contest

winner, for bringing

that to

my attention.

The idea is called phase

addi-

tion, and

its block diagram

ap-

pears

in Fig. 1. What you do

is

route a digital

word

to

a D/A con-

verter that

is followed by a

low -

pass

filter, just as

we

did before.

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