Elenco Electronics AK-500/K-39, AK-500, K-39 Assembly And Instruction Manual

LOVE TESTER KIT

MODEL AK-500/K-39

Assembly and Instruction Manual

ElencoTMElectronics, Inc.

Copyright © 1994 ElencoTMElectronics, Inc. Revised 2003 REV-D 753239

PARTS LIST

Contact ElencoTMElectronics (address/phone/e-mail is at the back of this manual) if any parts are missing or
damaged. 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, R8 470W 5% 1/4W yellow-violet-brown-gold 134700
1 R5 15kW 5% 1/4W brown-green-orange-gold 151500
1 R2 56kW 5% 1/4W green-blue-orange-gold 155600
1 R7 68kW 5% 1/4W blue-gray-orange-gold 156800
1 R3 100kW 5% 1/4W brown-black-yellow-gold 161000
1 R4, R6 1.5MW 5% 1/4W brown-green-green-gold 171500

CAPACITORS

Qty. Symbol Value Description Part #

1 C1 .0039mF (392) Mylar 233917
1 C2 .015mF (153) Mylar 241517
1 C3 2.2mF 50V Electrolytic (Lytic) 262247
1 C4 47mF 16V Electrolytic (Lytic) 274744

SEMICONDUCTORS

Qty. Symbol Value Description Part #

1 D1 1N4148 Diode 314148
1 Q1 2N3904 Transistor 323904
1 U1 4011 Integrated Circuit (IC) 334011
1 U2 4017 Integrated Circuit (IC) 334017
8 LED 1 - 8 Light Emitting Diode (LED) 350001

MISCELLANEOUS

Qty. Description Part #

1 PC Board 517017
1 Dimple Switch 546101
1 Battery Snap 590098
1 Buzzer Piezoelectric 595201
1 Filter Red 621425
1 Spacer 7/32” 624008

PARTS IDENTIFICATION

Resistor

Diode

Battery Snap

Capacitors

Electrolytic

Mylar

Qty. Description Part #

1 Tape 2-sided 1” 748127
1 Cushion Tape 1” 790006
1 Wire Red 22ga. 1” 814220
1 Wire Bare 24ga. 1” 835000
1 Solder Tube 9ST4

Switch

Dimple

Buzzer

Integrated Circuit

IC Socket

LED

Transistor

-1-

IDENTIFYING RESISTOR VALUES

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

Bands

1 2

Multiplier

Tolerance

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

Tolerance

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

5%

3%

.1%

IDENTIFYING CAPACITOR VALUES

Capacitors will be identified by their capacitance value in pF (picofarads), nF (nanofarads), or mF (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

Multiplier

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

10%

The letter J indicates a tolerance of +5%

For the No.01234589
Multiply By 1 10 100 1k 10k 100k .01 0.1

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

INTRODUCTION

Want to know what kind of lover you are? Push the PRESS button and the Love Tester will rate you as a
lover. The Love Tester has eight Light Emitting Diodes (LEDs) that are driven ON and OFF one at a time
in sequence. When the PRESS button is pushed, the LEDs will flash and the buzzer will sound. After a
brief period of time, only one LED will remain lit. Above the lit LED is your rating as a lover, anywhere from
Cold Fish to Hot Stuff. In a minute or two, the LED will get dim and gradually go out.

THEORY OF OPERATION

Figure 1 shows the block diagram of the Love Tester circuit. It consists of two oscillators and eight LEDs driven
by a decade counter. One oscillator drives the decade counter and the oscillators are controlled by two timers.
We shall proceed to study the circuit in detail.

LEDs

Figure 1

B+

BUTTON

PRESS

Timer 1

OSC 1

Decade
Counter

OSC 2

Timer 2

Buzzer

-2-

THE DECADE COUNTER

The 4017 IC is a 5 stage divide by 10 counter. Figure 2 shows a diagram of this IC. This
IC has 10 outputs and a clear input. Only one of the 10 outputs will be high at any given
time. The other 9 will be low. Let’s assume that output 1 is high. If a pulse is fed into the
clock input, output 1 will go low and output 2 will go high. Each clock pulse will move the
output one position. Connect an LED to the output, it will light only when the output goes
high. It is obvious that when the clock is running, the LEDs will flash on and off with the
speed of the clock. When the clock stops, only one LED will be lit.

In this design, 8 LEDs are used per IC, but the counter has 10 outputs. If the clock stops
at an output without an LED, nothing will light. To prevent this, the 4017 IC is reset after
hitting the 8th output. This is simply done by tying the 9th output to the clear pin (pin 9
and pin 15 shorted together).

Block Diagram

14

1

15

Clock

Clock

Enable

Reset

Q0
Q1
Q2
Q3
Q4
Q5
Q6
Q7
Q8
Q9

OUT

C

VDD - Pin 16

VSS - Pin 8

3
2
4
7
10
1
5
6
9
11
12

THE LIGHT EMITTING DIODES (LED)

Figure 2

The operation of the LED is very simple. When current flows through the LED, it will emit
light. Note that the LED is connected between an IC output and ground through a resistor. When the IC output goes high,
the LED will light. The resistor limits the current so that the LED will not be damaged.

OSCILLATORS

The Love Tester uses two oscillators. The first oscillator produces a frequency of about 20 hertz (cycles) and the other
produces a frequency of about 2000 hertz. Figure 3 shows the basic oscillator
circuit. The 4011 integrated circuit (IC) contains four two-input NAND gates. Two
of these NAND gates are needed to form an oscillator. Feed back for this
oscillator is via capacitor C2 and resistors R4 and R5. These elements

R5

determine the frequency of oscillation. Both IC1 and IC2 act as inverters, that
is, when the input is low, the output is high. As long as pin 13 of IC1 is high, the
circuit will oscillate. If pin 13 is brought low, the circuit will stop oscillating.

The second oscillator is similar to the one described except for a difference in its
frequency controlling components, capacitor C1 and resistors R2 and R3. C1

Pin 13

+V

IC1

4011 IC

Figure 3

and R2 are smaller values causing the oscillator to oscillate at a much higher frequency. Pin 6 of the first NAND gate is
brought high at a 20 cycles rate. This causes the second oscillation to be chopped up at the first oscillation frequency rate
as shown in Figure 4. This combination produces the unusual sound heard from the buzzer.

C2

R4

IC2

BUZZER

The Love Tester buzzer consists of a piezoelectric material on a metal base. When a voltage is applied to piezoelectric
material, its dimensions change. The buzzer is connected to the 2kHz oscillator. When the oscillator runs, the changing
dimensions to the piezoelectric buzzer act like the cone of a speaker to set up sound waves.

TIMER

Timer 1 is made up of capacitor C3 and R6. Timer 2 is made up of capacitor C4 and R7 (see schematic diagram). When
S1 is pushed, both capacitors charge up to 9 volts and the oscillators run. When the switch is released, capacitor C3
discharges through resistor R6 and capacitor C4 discharges through resistor R7 and the base of Q1.

Note that C3 is tied to pin 13 of the 4011 IC. Thus, when capacitor C3 loses its charge, the circuit stops oscillating. The
buzzer stops and a single LED remains lit. After a minute or two, C4 loses its charge and removes the base current from
Q1. Q1 is in the ground return path of the LEDs and both ICs. Thus, when Q1 is turned off, the LED goes out. Only a very
small leakage current is then drawn from the battery. This current is so small that no ON/OFF switch is required.

Figure 4

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