Elenco Burglar Alarm User Manual

BURGLAR ALARM KIT

MODEL K-23

Assembly and Instruction Manual

Copyright © 2013, 1989 ELENCO®Electronics, Inc. Revised 2011 REV-Q 753223

No part of this book shall be reproduced by any means; electronic, photocopying, or otherwise without written permission from the publisher.

ELENCO

®

PARTS LIST

If you are a student, and any parts are missing or damaged, please see instructor or bookstore.
If you purchased this kit from a distributor, catalog, etc., please contact ELENCO®(address/phone/e-mail is at
the back of this manual) for additional assistance, if needed. DO NOT contact your place of purchase as they
will not be able to help you.

RESISTORS

Qty. Symbol Value Color Code Part #

! 2 R1, R2 39kΩ 5% 1/4W orange-white-orange-gold 153900

CAPACITORS

Qty. Symbol Value Description Part #

! 1 C2 0.1µF (104) Mylar 251017
! 1 C1 47µF Electrolytic 274744

SEMICONDUCTORS

Qty. Symbol Value Description Part #

! 2 D1, D2 1N4001 Diode 314001
! 1 SCR1 C106B1 or T106B1 SCR 319106

MISCELLANEOUS

Qty. Symbol Description Part #

! 1 PC board 518023
! 1 S1 Switch 541102
! 1 B1 Battery snap 590098
! 1 A1 Buzzer 595203
! 1 4” Black wire 814120
! 5 4” Blue wire 814620

-1-

Resistor

Capacitor

PARTS IDENTIFICATION

Electrolytic

SCR

Switch

Diode

Mylar

Battery Snap

Buzzer

OR

The Elenco®Burglar Alarm is designed to operate
from 9-15VDC. The silicon controlled rectifier is the
heart of the Burglar Alarm. This device is an
electronic switch that allows current to flow only in
one direction. Figure 1 shows a simple circuit of an
SCR. When a positive voltage is applied to the
anode and a negative voltage to the cathode, no
current will flow.

INTRODUCTION

-2-

Figure 1

IDENTIFYING CAPACITOR VALUES

Capacitors will be identified by their capacitance value in pF (picofarads), nF (nanofarads), or µF (microfarads).
Most capacitors will have their actual value printed on them. Some capacitors may have their value printed in
the following manner.

Second Digit

First Digit

Multiplier

Tolerance

The above value is 10 x 1,000 = 10,000pF or .01µF
The letter K indicates a tolerance of +10%
The letter J indicates a tolerance of +5%

For the No. 0 1 2 3 4 5 8 9

Multiply By 1 10 100 1k 10k 100k .01 0.1

Multiplier

Note: The letter “R” may be used at times to
signify a decimal point; as in 3R3 = 3.3

IDENTIFYING RESISTOR VALUES

Use the following information as a guide in properly identifying the value of resistors.

BAND 1

1st Digit

Color Digit
Black 0
Brown 1
Red 2
Orange 3
Yellow 4
Green 5
Blue 6
Violet 7
Gray 8
White 9

BAND 2

2nd Digit

Color Digit
Black 0
Brown 1
Red 2
Orange 3
Yellow 4
Green 5
Blue 6
Violet 7
Gray 8
White 9

Multiplier

Color Multiplier
Black 1
Brown 10
Red 100
Orange 1,000
Yellow 10,000
Green 100,000
Blue 1,000,000
Silver 0.01
Gold 0.1

Resistance

Toler ance

Color Tolerance
Silver +10%
Gold +5%
Brown +1%
Red +2%
Orange +3%
Green +.5%
Blue +.25%
Violet +.1%

Bands

1 2

Multiplier

Tolerance

103K

100

The Elenco®Burglar Alarm is designed to set off an
alarm whenever the circuit is activated. There are
two ways of activating the alarm; by opening a
contact switch and/or by shorting a contact switch.
Once the alarm is ON, returning the switch back to
its original position will not turn off the alarm. A third

switch controls the turn-off of the alarm. There is no
limit to the number of the switches that can be
placed to protect your property. You may use one for
each window and door in your house. There also is
a feature that allows use of the alarm to protect your
automobile and auto accessories.

POWER SUPPLY

Electrolytic capacitors have a positive and a negative
electrode. The negative lead is indicated on the
packaging by a stripe with minus signs and possibly
arrowheads. Also, the negative lead of a radial
electrolytic is shorter than the positive one.

Polarity
marking

(+)

(–)

-3-

When we place a voltage to the gate, a current will
flow between the anode and cathode turning ON
the alarm buzzer. If we remove the voltage on the
gate, the current will continue to flow in the SCR.

Thus, if a burglar opens the door, the alarm will go
off. Closing that door will not turn off the alarm, it will
continue to sound. The only way to turn it off is to
remove the power to the SCR.

ACTIVATING SWITCHES

There are two types of activating switches, the
normally open (N.O.) contacts and normally closed
(N.C.) contacts. Figure 2A shows the N.O. circuit.
Remember that the SCR needs gate voltage to fire.
When the N.O. switch is closed, the SCR will
conduct current and continue to do so even if the
N.O. switch is opened.
Figure 2B shows the circuit for a N.C. switch. Here,
while the switch is closed, no voltage will be seen at
the gate of the SCR. Once the switch is open, the
SCR will conduct and continue to do so until the
voltage is removed from the anode of the SCR. This
important turn on / no turn off feature prevents the
intruder from turning off the alarm. When we combine
the N.O. and the N.C. circuits, a problem occurs. The
N.C. switch will short out the N.O. switch voltage. To
prevent this, we add a diode to isolate the two
circuits. Figure 3 shows this circuit. The diode D2
prevents the voltage from being shorted out through
the N.C. switch. Voltage from R1 will pass through
the diode and into the gate of the SCR when SW
N.C. is open.

Figure 2A Figure 2B

Figure 3

When this alarm is used in an automobile, any
jarring of the contact switches may set off the alarm.
To prevent this, a capacitor (C2) is added to the
circuit. Figure 3 shows the location of C2. When the
N.C. or N.O. switch is first activated, the current
through R1 or R2 first goes to charge the capacitor.
After the capacitor is charged, then the voltage will

build up enough to trigger the SCR. The time may
seem very fast, but in electronics, it is a long time
when you consider circuits react in microseconds
(0.000001 sec.). Thus, by adding capacitor C2, any
noise spike shorter than one millisecond will not fire
the alarm.

ELIMINATING FALSE ALARMS

The alarm device used in this circuit is a buzzer.
This device operates by vibrating back and forth,
interrupting the current. Remember that the SCR
will turn off if the gate has no voltage and the anode
also loses its voltage to the anode, a capacitor (C1)
is added across the buzzer, as shown in Figure 4.

This capacitor will
keep the current
flowing in the SCR
whenever the buzzer
opens up.

KEEPING THE ALARM ON

The Burglar Alarm can be used to control a relay,
such as the relay in your auto horn system. To do so,
simply replace the buzzer with the relay. Whenever
the alarm is fired, the relay will close, setting off the

alarm. A diode (D1) is placed across the relay to
remove the excessive voltage generated by the
relay coil from damaging the SCR.

EXTERNAL ALARM

Figure 4

-4-

CONSTRUCTION

Solder

Soldering Iron

Foil

Solder

Soldering Iron

Foil

Component Lead

Soldering Iron

Circuit Board

Foil

Rosin

Soldering iron positioned
incorrectly.

Solder

Gap

Component Lead

Solder

Soldering Iron

Drag

Foil

1. Solder all components from the
copper foil side only. Push the
soldering iron tip against both the
lead and the circuit board foil.

2. Apply a small amount of solder to
the iron tip. This allows the heat
to leave the iron and onto the foil.
Immediately apply solder to the
opposite side of the connection,
away from the iron. Allow the
heated component and the circuit
foil to melt the solder.

1. Insufficient heat - the solder will

not flow onto the lead as shown.

3. Allow the solder to flow around
the connection. Then, remove
the solder and the iron and let the
connection cool. The solder
should have flowed smoothly and
not lump around the wire lead.

4.

Here is what a good solder
connection looks like.

2. Insufficient solder - let the

solder flow over the connection
until it is covered.
Use just enough solder to cover
the connection.

3. Excessive solder - could make

connections that you did not
intend to between adjacent foil
areas or terminals.

4. Solder bridges - occur when

solder runs between circuit paths
and creates a short circuit. This is
usually caused by using too
much solder.
To correct this, simply drag your
soldering iron across the solder
bridge as shown.

What Good Soldering Looks Like

A good solder connection should be bright, shiny, smooth, and uniformly
flowed over all surfaces.

Types of Poor Soldering Connections

Introduction

The most important factor in assembling your K-23 Burglar Alarm Kit is
good soldering techniques. Using the proper soldering iron is of prime
importance. A small pencil type soldering iron of 25 watts is
recommended. The tip of the iron must be kept clean at all times

and well-tinned.

Solder

For many years leaded solder was the most common type of solder
used by the electronics industry, but it is now being replaced by lead­free solder for health reasons. This kit contains lead-free solder, which
contains 99.3% tin, 0.7% copper, and has a rosin-flux core.

Lead-free solder is different from lead solder: It has a higher melting
point than lead solder, so you need higher temperature for the solder to
flow properly. Recommended tip temperature is approximately 700OF;
higher temperatures improve solder flow but accelerate tip decay. An
increase in soldering time may be required to achieve good results.
Soldering iron tips wear out faster since lead-free solders are more
corrosive and the higher soldering temperatures accelerate corrosion,
so proper tip care is important. The solder joint finish will look slightly
duller with lead-free solders.

Use these procedures to increase the life of your soldering iron tip when
using lead-free solder:

● Keep the iron tinned at all times.

● Use the correct tip size for best heat transfer. The conical tip is the

most commonly used.

● Turn off iron when not in use or reduce temperature setting when
using a soldering station.

●

Tips should be cleaned frequently to remove oxidation before it becomes
impossible to remove. Use Dry Tip Cleaner (Elenco®#SH-1025) or Tip
Cleaner (Elenco®#TTC1). If you use a sponge to clean your tip, then use
distilled water (tap water has impurities that accelerate corrosion).

Safety Procedures

● Always wear safety glasses or safety goggles to
protect your eyes when working with tools or
soldering iron, and during all phases of testing.

● Be sure there is adequate ventilation when soldering.

●

Locate soldering iron in an area where you do not have to go around
it or reach over it. Keep it in a safe area away from the reach of
children.

● Do not hold solder in your mouth. Solder is a toxic substance.
Wash hands thoroughly after handling solder.

Assemble Components

In all of the following assembly steps, the components must be installed
on the top side of the PC board unless otherwise indicated. The top
legend shows where each component goes. The leads pass through the
corresponding holes in the board and are soldered on the foil side.

Use only rosin core solder.

DO NOT USE ACID CORE SOLDER!

ASSEMBLE COMPONENTS TO THE PC BOARD

-5-

Figure C

Diodes have polarity. Mount
them with the band in the
correct direction, as shown
on the PC board.

A1 - Buzzer

C1 - 47µF Electrolytic Cap.

(see Figure A)

SCR1 - SCR (106B1)

(see Figure B)

D1 - 1N4001 Diode

(see Figure C)

R2 - 39kΩ 5% 1/4W Resistor

(orange-white-orange-gold)

C2 - .1µF (104) Mylar Cap.

D2 - 1N4001 Diode

(see Figure C)

Black

Red

Blue

B1 - Battery Snap -

Insert the red
and black wire through the hole in the PC
board as shown. Install the red wire into
the positive (+) hole and the black wire into
the negative (–) hole. Solder and cut off
the excess leads.

S1 - Slide Switch

R1 - 39kΩ 5% 1/4W Resistor

(orange-white-orange-gold)

Figure B

Mount the SCR in the same direction as marked on
the PC board. Be sure that the metal backing is in the
direction shown.

Metal

Backing

With Beveled Edge

Figure A

Electrolytic capacitors have polarity.
Be sure to mount them with the
negative (–) lead (marked on side) in
the correct hole.

Warning: If the
capacitor is
connected with
incorrect polarity,
it may heat up
and either leak or
cause the
capacitor to
explode.

Polarity

marking

(–) (+)

-6-

QUIZ

1. The Burglar Alarm is powered by a _______ volt battery.

2. The main component of the Burglar Alarm is the ___________________.

3. The two types of activating switches are the normally __________ contact and the normally __________
contacts.

4. The SCR will only conduct current when the __________ is at a positive voltage.

5. An SCR will continue to conduct current from Anode to Cathode even if the gate is _____________.

6. Once the SCR is fired, one way to turn it off is to _______________ the anode voltage.

7. False alarms are eliminated by the use of a _____________.

8. The alarm device used in this circuit is an electronic ________________.

9. Capacitor ______ is added across the buzzer to keep the current flowing in the SCR.

10. Diode D1 is added across the relay to remove excessive _________ to the SCR.

TESTING INSTRUCTIONS

1. Connect a 9V type battery to the battery snap

(battery not included).

2. Switch S1, power switch, on (up position).

3. Short two wires connected to S3 together, buzzer

should activate. Disconnect the wires from S3,
the buzzer should still be on. Turn off S1 (down
position) to reset the alarm.

4. Turn S1 on (up position). Disconnect the wires
from S2 and the buzzer should activate.
Reconnect the wires to S2, the buzzer should still
be on. Turn off S1 to reset the alarm.

5. If your K-23 does not operate properly, follow the
troubleshooting procedure below.

TROUBLESHOOTING

1. One of the most frequently occurring problems is
poor solder connections.

a) Tug slightly on all parts to make sure that

they are indeed soldered.

b) All solder connections should be shiny.

Resolder any that are not.

c) Solder should flow into a smooth puddle

rather than a round ball. Resolder any
connection that has formed into a ball.

d) Have any solder bridges formed? A solder

bridge may occur if you accidentally touch
an adjacent foil by using too much solder or
by dragging the soldering iron across
adjacent foils. Break the bridge with your
soldering iron.

2. Be sure that all components have been mounted
in their correct places.

a) Make sure that C1, the electrolytic

capacitor, is mounted correctly.

b) Make sure that diodes D1 and D2 are

mounted correctly with the band in the same
direction as shown on the top legend.

c) Make sure that the battery snap B1 is

installed correctly. The red wire should be in
the positive (+) hole and the black wire in
the negative (–) hole.

d) Make sure that the buzzer is wired correctly

(blue wire to (+) lead).
e) Make sure that the SCR is in correctly.
f) Use a fresh 9 volt battery.

Contact ELENCO®if you have any problems. DO NOT contact your place of purchase as they will not be able
to help you.

AUTO ALARM

You will not mount parts A1, B1 or S1. When someone opens a door or tries to remove the radio, the alarm

is activated and the car horn will sound (see schematic diagram below).

Connect to your car as follows. See diagram below.

Connect P4 to the wire running from the door switch to the dome light.
Connect P1 to the wire running from the horn relay to the horn switch, which is located in the steering wheel.
Connect P2 to an alarm turn-off switch (use S1, be sure to use the middle lug for one of the connections).

Connect the other end of the switch to the car battery via fuse box.
Connect P9 to the metal casing on the radio which is grounded. When the lead is separated from the ground,
the alarm will be activated and the horn will sound. If you do not want to protect a sound system, connect the
lead permanently to a ground.

Connect P10 to the car ground.

SCHEMATIC DIAGRAM

Attach a fresh 9 volt battery to the battery snap.
Connect the leads from S2 to any normally closed
switch. If you do not wish to use this switch, simply
connect these leads together. Connect the leads
from S3 to any normally open switch. When either

S2 is opened, or S3 is closed, the alarm will turn on
and stay on even if switches S2 and S3 are
switched back. To reset the alarm, turn switch S1
off and then back on again. A key lock switch can
be substituted for S1.

Auto Door Alarm Connection

Car Horn Connection

Radio Alarm Connection

Dome Light

N.O. (Door SW.)

12V

P4

Horn SW.

Horn Relay

Horn

12V

12V

P2

P1

P10

P9

Radio

SCR

Foil Side of

PC Board

ELENCO

®

150 Carpenter Avenue

Wheeling, IL 60090

[phone]

Website: www.elenco.com

e-mail: [e-mail]

OPERATING PROCEDURES (Auto Alarm)

SCHEMATIC DIAGRAMS FOR AUTO ALARM

Answers: 1. 9; 2. Silicon Controlled Rectifier (SCR); 3. open, closed; 4. gate;

5. negative; 6. remove; 7. capacitor; 8. buzzer; 9. C1; 10. voltage