1957年美国电子实验者手册：探索早期模电实验

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"《电子实验手册1957-美国》是1957年出版的一本面向电子爱好者的杂志，包含了许多模拟电子（模电）的实用实验项目。书中介绍的技术较为原始，适合初学者和业余爱好者学习。杂志提到了一些特色内容，如晶体管便携设备、电视静音器、技术人员的频带转换器和音箱封装设计等。此外，还推广了一种只需$500的月付计划，以及WRL的印刷电路屏调制器套件和全新的91062 ClanvgXit发射机。" 这篇摘要中提到的知识点包括： 1. **晶体管技术**：在1957年的背景下，晶体管是相对较新的技术，它取代了真空管在许多电子设备中的应用，具有更小的体积、更低的功耗和更高的可靠性。手册中提到的“Transistor Portables”可能涉及如何使用晶体管制作便携式电子设备。 2. **电视静音器(Television Commercial Silencer)**：这是一个实用的装置，可能通过断开音频信号或干扰电视接收来实现商业广告时段的静音，为早期电视用户提供了便利。 3. **频带转换器(Technician's Band Converter)**：在无线电通信中，频带转换器用于改变信号的频率范围，以适应不同的广播频段。这可能是针对业余无线电爱好者或技术工人的一个实验项目。 4. **音箱封装设计($3 Speaker Enclosure)**：音箱的结构设计对声音质量有重大影响。手册可能包含了制作音箱外壳的步骤和建议，帮助读者理解如何构建一个有效的音箱系统。 5. **印刷电路板(Printed Circuit Board, PCB)**：WRL的印刷电路屏调制器套件强调了使用PCB进行组装，这在当时是一个先进的制造方法，简化了电路的构造和维护。 6. **调制器(Modulator)**：调制器是将音频信号附加到射频信号上的设备，以便在无线电信号中传输声音。此处提到的调制器适用于多种发射机，如WRL Globe Chief和其他品牌如Heath AT-1、Johnson Adventurer和Knight 50瓦特等。 7. **Xmttr. (发射机)**：91062 ClanvgXit是一个全波段切换发射机，覆盖了160-10M的频段，适合90瓦的功率输出。特别的是，它为新手提供了15瓦的刻度指示。 8. **初学者友好**：手册和其中的项目似乎特别考虑了初学者和业余爱好者的需求，例如15瓦的功率指示和调制器的简单组装设计。这些知识点展示了1957年时电子技术的发展水平和业余爱好者的学习兴趣，涵盖了从基础元件到复杂设备的多个层面，为当时的电子爱好者提供了一个丰富的学习资源。

Fig. 2. Under -chassis view of unit shows location of the major components.

about one ohm to hundreds of thousands

of ohms. Correctly used, they enable the

builder to meet the following performance

specifications:

(1) Low initial cost-the relative sim-

plicity of the circuit brings the over-all

initial cost down to about $11.50.

(2) Low operating cost-the choice of a

high -resistance thermistor coupled with a

low -current sensitive relay permits the cir-

cuit to idle continuously with a current

drain of something under .002 amPere. At

present power rates, this makes the yearly

operating ,cost less than 24 cents.

(3) Reliability-alarms

of this type

should be inspected and checked periodical-

ly to insure reliability of operation in time

of need. Since all circuit components op-

erate at less than half -maximum rating,

and

because

the relay and rectifier are en-

closed in a metal case which is as close to

being dust -proof as one could desire, de-

pendability is assured even though the test -

checks are few and far between.

(4) Remote control-to make the device

universally applicable, components and de-

sign factors were selected to permit the

builder to use very long leads-literally

thousands of feet, if desired-between the

thermistor and the control box. Even the

alarm bell may be placed, hundreds of feet

from the control section should this sep-

aration be desirable.

(5) Adjustable sensitivity-to satisfy in-

dividual requirements, the circuit

ar-

ranged so that it can be made to react

swiftly to almost any above -normal tem-

perature between 120 and 500° F or higher.

Fig. 3. Schematic diagram and parts list for the thermistor fire alarm.

Cl-8-µfd., 450 -volt electrolytic capacitor

R1 -10,000 -ohm, 1

-watt resistor

rating 1 to 2

ma. (Advance SO -IC -10,000D,

Sigma 2F, or equivalent)

R2 -100,000 -ohm potentiometer,

linear

taper

SRI -65 -ma. selenium rectifier (see text)

(1RC Q-11-128 or equivalent)

TI-Filament transformer, 6.3 volt (l 1.2 amp.

RLI-Sensitive relay, 10,000 -ohm coil, pull -in

(Stancor P-6134 or equivalent)

TH1-Thermistor, VECO Type 51R2 (Victory

RI 10K

Engineering

Corporation,

Springfield Rd.,

Union, N. J.-a kit of thermistors and varis.

tors, available from the company for 510.00

by mail, contains this thermistor)

SRI

CI IOOK

BELL

1-Line cord and plug

Byfd.

1-Standard doorbell or buzzer

41EN

TH I

1-Case, aluminum, gray hammertone finish,

S1' x 3V2" x 2t/8"

4=Insulated binding posts

1 -2 -lug tie point

I-Potentiometer knob, any type

RLI

Misc. grommets, machine screws, wire, solder,

etc.

ELECTRONIC EXPERIMENTER'S HANDBOOK

Fig. 4. Pictorial diagram of the alarm.

(6)

Latch -in feature-once the fire alarm

is triggered, the alarm bell continues to

ring even though the heat around the ther-

mistor sensing element temporarily sub-

sides. This action is accomplished auto-

matically by adjusting the relay properly,

as will be described later.

(7) No BX cable or conduit required-

low-voltage wires may be run between the

bell and central control.

Construction

Whether the reader duplicates the alarm

system exactly or makes modifications to

suit his tastes, just a few preliminary con-

structional precautions are desirable. The

rectifier (SR1, Fig. 3) should be rated at

35 ma. at the least, even though the total

current drain is less than 2 ma.; this makes

for cool operation over extended periods of

time.

Filter capacitor Cl, an 8-µfd. unit,

should have a working voltage rating of

450 volts although the total anticipated po-

tential across it never exceeds 150 volts;

long capacitor life may be expected under

these conditions. The transformer Ti may

be mounted either inside or outside.

Terminals for the thermistor are isolated

from the line by the 10,000 -ohm resistance

of the relay and by a protective 10,000 -ohm

resistor Rl. An even better arrangement

would be to use an isolating transformer,

such as the Triad R54X. This unit has a

115 -volt secondary for operating the ther-

mistor and relay circuit, thus completely

isolating it from the line. Also included is

a 6.3 -volt winding for operating the alarm

bell. With such an arrangement, the relay

contacts would be connected in series with

1957 Edition

METER

O-5 MA

0-10 MA.

75K 1/zw.

RESISTOR

11111

THERMISTOR

BINDING

POSTS

Fig. 5. Hookup for initial adjustments.

the 6.3 -volt winding and the alarm bell.

The binding posts are insulated from the

case by means of shoulder or extruded fiber

washers. Holes drilled to take these wash-

ers must be large enough to allow the ex-

trusion to "sit" inside the rim of the open-

ing, thus preventing the metal screw of the

post from touching the case. Live rubber

grommets are

necessary

for the feed -

through leads to protect the latter against

fraying over the years.

Testing and Adjustment

All wiring should be completed before

proceeding with adjustment and testing.

A.c. power should not be applied until it

is determined, by means of an ohmmeter,

that no bare wires are in contact with the

case and that there are no short circuits

which might injure the selenium rectifier,

the thermistor, or the relay. An ohmmeter

is mentioned because it is usually a part

of a multitest meter which is needed for

current measurements.

Fo"r the following test, do not connect

the thermistor into the circuit at all.

In-

stead, connect the multitester as a low -

range milliammeter (0-10 ma. range is just

about right) in series with a 75,000 -ohm

resistor across the thermistor binding posts

17'

as shown in Fig.

To avoid raucous

buzzing or bell -ringing during the test, a

6 -volt pilot lamp may be substituted for

the alarm signal device as an indicator.

First rotate the knob of the sensitivity

control R2 so that it presents maximum

resistance to the series circuit (fully clock-

wise in this model), then insert the a.c.

plug into a 117 -volt a.c. outlet. The milli

ammeter should show a reading of a small

fraction of a milliampere.

Gradually ro-

tate the potentiometer while watching the

meter and the pilot indicator, noting the

current

at which the

pilot lamp

first

lights up. This is the "pull -in" current of

the relay. Adjust the relay according to

the manufacturer's instructions (these ac-

company the relay when purchased)

that it pulls in at 2 ma. and drops out at

an appreciably lower figure, such as .8 ma.

to 1 ma. Once this adjustment has been

made, it is advisable to seal the adjusting

screws with flexible polystyrene coil dope.

Again rotate R2 to maximum resistance

and replace the 75,000 -ohm resistor with

the thermistor, leaving the meter connect-

ed. Repeat the "creep -up" procedure given

above, adjusting the potentiometer in small

steps.

This is necessary because, as the

current is allowed to rise in the thermistor

and it begins to warm up, its resistance

diminishes, permitting more current to

flow.

The increased flow of current, in

turn, warms it some more, again reducing

resistance. This cycle continues until the

thermistor radiates its heat away as fast

as it is generated, stability being reached

in about ten seconds. From the above pro-

cedure, determine the position of the con-

trol knob for a setting which is just short

of pull -in. Leave the control in this posi-

tion, remove the meter, and connect the

thermistor alone across the binding posts.

The alarm is now set for a heat test.

Pass a lighted match quickly under the

thermistor body; the pilot lamp should

come on instantly, simulating ringing of

the alarm bell. Once the correct setting of

R2 has been obtained, the response should

bé instantaneous when the ambient tem-

perature around the sensing element ex-

ceeds 120-150° F.

-{{-

Electronic Baby Sitter

By BYRON G. WELLS

Listen

the baby from another room-or

another house-with this sound amplifier

HIS versatile unit is easy to build and

low in cost, and the results obtained

from it are most gratifying.

It is con-

tained in two boxes, one housing a mi-

crophone and an amplifier, the other the

loudspeaker. The two boxes are connected

by means of television twin -lead, which can

be of any length up to 150 feet. You can

place the unit with the microphone in any

convenient place in the baby's room and

the loudspeaker box in another toom of

the house where the parents are likely to

be-the bedroom, living room, etc.

It has

been used even between adjacent houses

or apartments with good results, permit-

ting neighbors to baby-sit for each other

without having to leave their own homes

or apartments.

The schematic shows that the circuit is

equivalent to the final two stages and

rectifier of a small a.c.-d.c. broadcast re-

ceiver, with a resistor in the filament cir-

cuit to produce a voltage drop equal to

that of the filaments of the two additional

tubes which normally appear in such a

receiver.

The placement of parts is not at all

critical. The microphone and volume con -

ELECTRONIC EXPERIMENTER'S HANDBOOK

Schematic diagram

of the Electronic Baby

Sitter. Follow this

and the pictorial wir-

ing diagram below

wiring

your

unit.

Notice

that

chassis

ground is not con-

nected to either side

of the power line.

---

12BA6

% °

5085

VI /

3+I +'4

VOLUME

CONTROL

xTALI

MIC.

35W4

~AM~

RI-I megohm audio taper pot. with switch,

("Volume Control")

R2-1000 ohm, 1/2 w. res.

R3-50,000 ohm, 1/2 w. res.

R4-250,000 ohm, 1/2 w. res.

R5-150 ohm, 1 w. res.

R6-150 ohm, 10 w. wirewound res.

R7-10,000 ohm, 1 w. res.

CI-.01 µfd., 400 v. capacitor

C2-.02 µfd., 400 v. capacitor

C3-.1 mid., 400 v. capacitor

C4-05-20/20 µ1d., 150 v. two -section elec. capacitor

S1-S.p.s.t. "Power" switch (on RI)

TI-Audio output trans. to match 10,000

ohms to

speaker voice coil (A universal output

trans.

such as the Stancor A-3856 may be

used.)

Vl-12BA6 tube

V2 -50B5 tube

V3 -35W4 tube

Xtal Mic.-High output or hearing -aid type

crystal

microphone

Loudspeaker-Small PM loudspeaker

Cabinet; chassis; terminal strip; line cord

and

plug; knob for volume control; screws, etc.

rol are mounted on the front of

the cabi-

net and the other parts on a

metal chassis.

Before finally mounting the parts,

posi-

tion them tentatively on the

chassis. Work

out an arrangement in which as

many as

possible of the wires between parts are

short and direct, but space the

components

far enough apart so that you

will not be

cramped when doing the actual

wiring.

In doing the wiring, follow the

schematic

and pictorial wiring diagrams

carefully,

solder all wires properly, and

make sure

that no short circuits are caused

by bare

wire or excess solder. If this is

done, the

unit should perform at the very

first try.

SOLDER

70 CHASSIS

S.P.S.T. POWER

SWITCH ISO ON

VOLUME CONTROL

LINE

PLUG

With the unit plugged -in in

the baby's

room and the

loudspeaker box in another

room, the volume can

be regulated to a

comfortable level.

The sensitivity is so

great that, with the

microphone fifteen

feet from the baby's crib, you can

hear

every breath the baby

takes. While this

is novel and makes a good

demonstration

of the unit,

also can be annoying, as

background noise, such as window

shades

and venetian blinds rattling,

also is am-

plified.

It is best to adjust the

volume so

that no noise comes through

until a higher

level of sound is reached, such as

the baby

crying.

5085

TUBE

idAw4,441)

TER.

STRIP

35W4

TUBE

1957 Edition

Inserting

one of the probes for the

watering control into place

on lawn.

The moisturemeter

is shown here

being used to check the condition

the soil

potted plant.

It can

also be used to check

moisture in a

lawn or garden soil, after

calibration.

Elewtroinie

G cadsets

for the

Ga rdeiner

Give electronics

the task of

controlling

your sprinkler

and indicating

when your

house plants need

watering

DID YOU EVER DREAM

that the sci-

ence of electronics might be

of help

to you in your gardening

activities? Prob-

ably not-it seems

rather

far-

fetched, imaginative, futuristic

dream even

to consider such a possibility.

But it is not far-fetched-in

fact, you

can build electronic equipment

right now

which will aid you

tremendously in both

inside and outside gardening

activities. The

first devit2 to be described

will actually

take over the problem

of watering the

lawn or garden and

perform such water-

ing automatically-keeping

the moisture

level of the soil at the

desired point.

And the second device

will permit you

to determine; quickly and

easily, whether

watering is necessary-either

outdoors or

in your "window garden."

This device uses

an ordinary meter, a single transistor,

and

a small battery.

Before going into the actual

construc-

tion details on these two

devices, we should

perhaps dwell a little

on the basic princi-

ples by means of which

both devices op-

erate.

Dry earth is a

very poor conductor of

electricity.

In fact, it might be

called a

fairly good insulator.

However, when earth

is moistened, the

story is different. Its

con-

ductivity increases greatly

until, with cer-

tain types of soil and

extremely moist con-

ditions, it can be called

a good conductor.

In between these extremes,

the resistance

varies over wide limits.

If we could contrive

some method of

measuring the soil

resistance when we

know moisture conditions

are optimum,

we would have a characteristic

which we

could use to control

external equipment,

such as a sprinkling

system, or which

would give an indication

of moisture con-

ditions on a meter. A

method for doing

each of these is covered

in this article.

Neither device is complicated,

and a de-

tailed knowledge of electronics

is not nec-

essary to understand the

operation of

either. And a lot of

construction experi-

ence is not required.

So, head for your workbench,

get out

the soldering iron (a low

-wattage one for

transistor circuits, please),

and build your-

self either or both of these

gadgets.

ELECTRONIC EXPERIMENTER'S

HANDBOOK

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