Elenco Electronics SM-200K User guide

SMT - TRAINING COURSE
MODEL SM-200K
Assembly and Instruction Manual
Surface Mount Technology Kit
Copyright © 2007, 2000 Elenco®Electronics, Inc. Revised 2007 REV-L 753200
No part of this book shall be reproduced by any means; electronic, photocopying, or otherwise without written permission from the publisher.
Elenco®Electronics, Inc.

Qty. Description Part #
1 PC Board 517008
1 Dimple switch 546101
1 Battery snap 590098
1 Buzzer 595201
1 Filter red 621424
Qty. Description Part #
1 Spacer 7/32” 624008
1" Tape double sided 748127
1" Cushion tape 790006
1" Wire red #22 solid 814220
1 Solder Lead-free 9LF99
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®Electronics (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 Marking Part #
6 J1,J2, P1-P4 0Ω0 196101
2 R7,R8 470Ω5% 1/8W 471 196344
1 R5 10kΩ5% 1/8W 103 196514
1 R1 15kΩ5% 1/8W 153 / 1502 196518
1 R4 56kΩ5% 1/8W 563 196556
1 R3 100kΩ5% 1/8W 104 196614
2 R2,R6 1.5MΩ5% 1/8W 155 / 1504 196758
CAPACITORS
Qty. Symbol Value Description Part #
1 C2 .0039μF 10% 50V Cap. chip 233997
1 C1 .015μF 10% 50V Cap. chip 241597
1C4 2.2μF 20% 10V Electrolytic (Lytic) 262220
1 C3 100μF 20% 10V Electrolytic (Lytic) 281020
SEMICONDUCTORS
Qty. Symbol Value Description Part #
1 D1 1N4148 SM Diode RA6J, A6, A2, or 5H 31BA16
1 Q1 3904 Transistor RIA, 1A, N71, 1AM, or KINC 32SM04
1 IC1 4011 4011 Integrated Circuit (IC) 33SM11
1 IC2 4017 4017 Integrated Circuit (IC) 33SM17
6 LED1-LED6 LTL907 Light Emitting Diode (LED) 350907
MISCELLANEOUS
-1-
Integrated Circuit LED Capacitors
PARTS IDENTIFICATION
Dimple Switch
Diode
Lytic
Resistor
471
Battery Snap
Buzzer
Integrated Circuit
Spacer

INTRODUCTION
Need help in making up your mind? Just ask the SM-200K Decision Maker. Press the ask button and the right
answer will be given to your question. The Decision Maker has six light emitting diodes (LEDs) that are driven
ON and OFF one at a time in sequence. When the ASK 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 the answer to the
question asked. In a minute or two the LED will get dim and gradually go out.
The SM-200K uses very small surface mounted components. By building this kit you will obtain an interesting
electronic device and also gain valuable experience in surface mount technology.
THEORY OF OPERATION
Figure 1 shows the block diagram of
the Decision Maker circuit. It consists
of 6 LEDs driven by a decimal counter
and two oscillators. One oscillator
drives the decimal counter and the
other drives a buzzer. The counter and
the oscillators are controlled by two
timers. We shall proceed to study the
circuit in detail.
DECADE COUNTER
The 4017 IC is a 5 stage divide by 10 counter. Figure 2 shows a
diagram of the IC. The 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 us assume that output 1 is high. If a pulse is fed to the
clock input, output 1 will go low and output 2 will go high. Each
clock pulse will move the output one position. If we 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 6 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 preset after hitting the 6th
output. This is done by tying the 7th output to the clear pin (pin 5
and pin 15 shorted together).
LIGHT EMITTING DIODES (LED)
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.
-2-
Figure 1
Figure 2
Timer 1 Osc 1
Decade
Counter
Osc 2
Timer 2
Button
Ask
B+
Buzzer
LEDs
Block Diagram
Clock
Clock
Enable
Reset
Q0
Q1
Q2
Q3
Q4
Q5
Q6
Q7
Q8
Q9
COUT
3
2
4
7
10
1
5
8
9
11
12
14
13
15
VDD = Pin 16
VSS = Pin 8

-3-
OSCILLATORS
The SM-200K uses two oscillators. The first oscillator produces
a frequency of about 2000 hertz (cycles per second) and the
other produces a frequency of about 20 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. Feedback for this oscillator is
via capacitor C1 and resistors R1 and R2. These elements
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 1 of IC1 is high the circuit will oscillate. If pin 1 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 C2 and resistors R3 and R4. C2 and R4 are smaller values causing the oscillator to
oscillate at a much higher frequency. Pin 8 of the first NAND gate is brought high at a 20 cycle 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.
BUZZER
The SM-200K buzzer consists of a piezoelectric material on a metal base. When a voltage is applied to a
piezoelectric material its dimensions change. The buzzer is connected to the 2kHz oscillator. When the
oscillator runs, the changing dimensions of the piezoelectric buzzer act like the cone of a speaker to set up
sound waves.
TIMERS
Timer 1 is made up of capacitor C4 and resistor R6. Timer 2 is made up of capacitor C3 and resistor R5 (see
schematic diagram). When switch S1 is pushed both capacitors charge up to 9 volts and the oscillators run.
When the switch is released, capacitor C4 discharges through resistor R6 and capacitor C3 discharges through
resistor R5 and the base of Q1.
Note that C4 is tied to pin 1 of the 4011 IC. Thus, when capacitor C4 loses its charge, the circuit stops
oscillating. The buzzer stops and a single LED remains lit. After a minute or two, C3 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 3
Figure 4

-4-
ASSEMBLY INSTRUCTIONS
INTRODUCTION
Assembly of your SM-200K Decision Maker will prove to be an exciting project and give much satisfaction and
personal achievement. If you have experience in soldering and wiring technique you should have no problem in
the assembly of this kit. Care must be given to identifying the proper components and in good soldering habits.
Above all, take your time and follow the easy step by step instructions. Remember, "An ounce of prevention is
worth a pound of cure". Avoid making mistakes and no problems will occur.
PARTS VERIFICATION
Before beginning the assembly process, familiarize yourself with the components and this instruction book.
Verify that all parts are present. This is best done by checking off each item against the parts list.
Care must be taken when handling the chip resistors and capacitors.
They are very small and are easily lost. Chip resistors are marked
with their component value. The first 2 digits are the first 2 digits of
the resistance in ohms. The last digit gives the number of zeros
following the first 2 digits. The resistor shown at right is therefore
3,900 ohms.
The values of the chip capacitors are not marked on the component. The two capacitors, .0039μF and .015μF,
are each in a separate bag with the component value marked on the bag. To avoid mixing these parts up, they
should not be taken out of their packages until just before they are soldered to the PC board. Sometimes these
parts are mixed, but can be identified by different color and quantities.
SAFETY PROCEDURES
• Wear eye protection when soldering and during all phases of construction.
• Locate soldering iron in an area where you do not have to go around it or reach over it.
•Do not hold solder in your mouth. Wash your hands thoroughly after handling solder.
• Be sure that there is adequate ventilation present.
SOLDERING TIPS
The most important factor in assembling your SM-200K Decision Maker is good soldering techniques. Using
the proper soldering iron is of prime importance. A small pencil type iron of 10-15 watts is recommended. A
sharply pointed tip is essential when soldering surface mount components. The tip of the iron should be kept
clean and well tinned at all times. Many areas on the printed circuit board are close together and care must be
given not to form solder shorts. Solder shorts may occur if you accidentally touch an adjacent foil, particularly
a previously soldered connection, using too much solder, or dragging the iron across adjacent foils. If a solder
short occurs, remove it with your hot iron. Use only rosin core solder. Before soldering the SM-200K board
should be taped to the workbench to keep it from moving when touched with the soldering iron. For a good
soldering job, the areas being soldered must be heated sufficiently so that the solder flows freely. When
soldering surface mount resistors and capacitors, the following procedure may be used:
1. Using tweezers, place the surface mount component on the PC board pads and secure in place with tape.
2. Apply a small amount of solder to the soldering iron tip. This allows the heat to leave the iron and flow onto
the foil.

-5-
3. Place the iron in contact with the PC board foil.
Apply a small amount of solder simultaneously to
the foil and the component and allow them to melt
the solder.
4. Remove the iron and allow the solder to cool. The
solder should have flowed freely and not lump up
around the component.
5. Remove the tape and solder the other side of the
component.
When soldering the transistors, diodes and
integrated circuits, the following procedure may be
used:
1. Place the component on the PC board pads and secure in place with tape.
2. Apply a small amount of solder to the soldering iron tip.
3. Place the soldering iron tip on top of the component lead to be soldered and apply solder simultaneously to
the lead and the PC board foil.
4. Remove the iron and allow the solder to cool. The solder should have flowed freely and not lump up around
the component.
After a component is completely soldered, each solder joint should be inspected with a magnifying glass. If the
solder has not flowed smoothly, a bad solder joint is indicated. This occurs when the component and pad have
not been heated sufficiently. To correct, reheat the connection and if necessary add a small amount of additional
solder.
Another way to solder surface mount components is
as follows:
1. Apply a small amount of solder to the soldering
iron tip.
2. Using tweezers, hold the component on the PC
board pads.
3. Apply the soldering iron simultaneously to the
component and pad and allow the solder to flow
around the component.
4. Remove the soldering iron and allow the
connection to cool.
Solder

-6-
PRACTICE
If you are unfamiliar with soldering surface mount components, it
would help to practice a bit before starting the assembly process. Six
0 ohm resistors, marked (000), are supplied with the SM-200K kit.
Only two are used in the assembly process. The other four may be
used for practice. Use the PC board area shown in Figure 5. If you
have not already done so, read the soldering tips in the previous
section. Try both of the methods described to see which you prefer.
SOLDER RESISTORS AND CAPACITORS TO PC BOARD
Be sure to read the section on soldering tips. Then follow the step by step instructions below. As each step is
completed, place a check mark in the box next to the instruction.
R4 - 56kΩResistor
(563)
R3 - 100kΩResistor
(104)
R5 - 10kΩResistor
(103)
C2 - .0039μF Capacitor
(value marked on bag)
J1 - 0ΩResistor
J2 - 0ΩResistor
(000)
C1 - .015μF Capacitor
(value marked on bag)
R2 - 1.5MΩResistor
R6 - 1.5MΩResistor
(155/1504)
R7 - 470ΩResistor
R8 - 470ΩResistor
(471)
R1 - 15kΩResistor
(153/1502)
0ΩResistors
Figure 5

-7-
SOLDER CAPACITORS AND SEMICONDUCTORS TO PC BOARD
D1 - Diode (1N4148)
(RA6J), (A6),
(A2) or
(5H)
C3 - 100μF Lytic
(See Figure 8)
Q1 - Transistor (3904)
(R1A), (1A),
(N71),
(1AM), or
(KINC)
LED 1
LED 2
LED 3
Figure 6
Mount IC with pin 1 as shown on the
PC board illustration.
Figure 7
Mount IC with pin 1 as shown on the
PC board illustration.
Figure 8
This capacitor is polarized, be sure
that the (+) and (–) sides are
positioned correctly.
Warning: If the capacitor is
connected with incorrect polarity, it
may heat up, and either leak or
cause the capacitor to explode.
Figure 9
This capacitor is polarized, be sure that the (+)
and (–) sides are positioned correctly.
Warning: If the
capacitor is connected
with incorrect polarity, it
may heat up, and either
leak or cause the
capacitor to explode.
IC2 - IC (4017)
(See Figure 7)
LED 4
LED 5
LED 6
C4 - 2.2μF Lytic
(See Figure 9)
IC1 - IC (4011)
(See Figure 6)
+
+
1
1
1
1

ASSEMBLE LARGE COMPONENTS TO PC BOARD
Place the buzzer on the
PC board with the white
center facing outward
and solder to the PC
board at the points shown
in Figure 10.
Strip 1/8 inch of
insulation off both ends of
the short red wire. Solder
the wire to the buzzer and
the PC board as shown in
Figure 10. Be sure the
wire is on the center
portion of the buzzer and
not on the outer rim.
Solder the red and black
battery snap wires to the
PC board as shown in
Figure 10.
Place the dimple switch,
domed upward, on the
PC board as shown in
Figure 11. Be sure none
of the contact points
touch the lead in foil to
the center ring of the
switch foil.
Peel one layer of the
protective backing off the
double sided scotch tape.
Place the tape over the
dimple switch as shown
in Figure 11. Press the
tape to the PC board and
peel off the remaining
protective backing.
Stick the 7/32 inch spacer onto the dimple
switch as shown in Figure 12.
Connect the 9V battery and push the spacer.
The buzzer should sound and the LEDs should
flash as described in the Introduction. If this
does not happen, refer to the Troubleshooting
section. The unit should be working before
completing the final assembly.
-8-
Figure 11
Figure 10 Red Black
Battery Snap
(+)
( )
Short Red Wire
Solder buzzer to
the PC board at
these points.
Lead in Foil
Contact
Points Tape

-9-
FINAL ASSEMBLY
Use scissors or single edge razor
blade to cut the thick cushion tape
into four 1/4 inch pieces. Peel off
one of the protective layers and
stick the tape to the corners of the
PC board as shown in Figure 12.
Peel the protective backing off the 3
X 4 1/2 inch red filter.
Remove the remaining protective
backing from the cushion tape.
Align the word ASK on the red filter
with the 7/32 inch spacer and stick
the filter to the cushion tape as
shown in Figure 12.
TROUBLESHOOTING
A) NO SOUND AND NO LEDs
1) Check that the battery snap is wired as shown in Figure 10.
2) Check that IC1 and IC2 are not installed backwards (see Figures 6 and 7). Be sure there are no solder
bridges between the IC pins.
3) Check that the dimple switch is mounted with the dome upward.
4) Check the value and the soldering of R5.
5) Check Q1.
B) SOUND BUT NO LEDs
1) Check that IC2 is not mounted backwards (see Figure 7). Be sure there are no solder bridges between the
IC pins.
2) Check the value and soldering of R8.
3) Check LED1 through LED6.
C) LEDs BUT NO SOUND
1) Check that the buzzer is soldered as in Figure 10. Check the solder connection between the jumper wire
and the center part of the buzzer.
2) Check for soldering bridges between the pins of IC1.
3) Check the value and the soldering of R3, R4, and R7.
D) LEDs STOP AS SOON AS SWITCH IS RELEASED
1) Check that C3 is mounted as shown in Figure 8.
2) Check that C2 is mounted as shown in Figure 9.
3) Check the value and soldering of R6.
4) Check D1.
Figure 12