Elenco Electronics K-40 User guide

TEMPERATURE ADAPTER KIT
MODEL TA-12/K-40
Assembly and Instruction Manual
Copyright © 2005, 1994 byElenco®Electronics,Inc. All rights reserved. Revised 2005 REV-C 753125
No partof this book shall be reproduced byanymeans; electronic,photocopying, or otherwise without written permission from the publisher.
Elenco®Electronics, Inc.

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 Description Color Code Part #
2 R5, R6 1kΩ5% 1/4W brown-black-red-gold 141000
1 R7 3.3kΩ5% 1/4W orange-orange-red-gold 143300
2 R1, R10 3.9kΩ5% 1/4W orange-white-red-gold 143900
2 R4, R9 10kΩ5% 1/4W brown-black-orange-gold 151000
1 R3 47kΩ5% 1/4W yellow-violet-orange-gold 154700
2 R2, R8 10kΩTrim Pot 191510
CAPACITORS
Qty. Symbol Description Part #
1 C1 .01µF, 50V (103) 241031
SEMICONDUCTORS
Qty. Symbol Description Part #
1 Q1 2N3904 NPN Transistor 323904
1U1 LM1458N Op-Amp Integrated Circuit (IC) 331458
1 U2 MC7805 5V Regulator 337805
MISCELLANEOUS
Qty. Description Part #
1 PC Board 518040
1 Solder Roll 24” 551124
1 BatterySnap 590098
1IC Socket 8-pin 664008
1 Alligator Clip Black 680001
1Alligator Clip Red 680002
1 Solid Black Wire 22ga. 6” 814120
1 Solid Red Wire 22ga. 6” 814220
1Cable 2 Conductor 24” 876090
1 #7 Shrink Tubing 1/2” 890050
1 3/16” Dia. Shrink Tubing 1 1/2” 890120
-1-
Resistor Transistor
PARTS IDENTIFICATION
Battery Snap
IC Socket
8-pin
Regulator Integrated
Circuit
PC Board
Capacitor
Alligator Clip Shrink
Tubing
#7
3/16”
Trim Pot

-2-
VOLTAGE REGULATOR
The MC7805 (U2) is the voltage regulator which is
used to supply a constant voltage of about 5V to the
circuit.
TEMPERATURE SENSOR
The Temperature Sensor is an NPN transistor
(2N3904). The NPN transistor has three
terminals: the collector,base,and emitter as
shown in Figure 1. When the collector and base of
this transistor are shorted together as shown in
Figure 2, they behave exactly like a diode, which is
atemperature-sensitive device. At a constant
current, the voltage across the base to emitter
junction decreases by approximately 1mV for
every 1OFincrease in temperature.
OP-AMP
The op-amp (LM1458) has twoinput terminals and
one output terminal. Figure 3 shows the op-amp
symbol. Terminals 1 and 2 are the input terminals,
and terminal 3 is the output
terminal. Many op-amps use
twoDC power supplies. The
twoterminals, 4 and 5, are
connected to a positivevoltage
(V+) and negative voltage
(V–), respectively. The TA-
12/K-40 uses a single supply
with ground tied to the V–
input.
The op-amp senses the difference between the
voltage signals applied at its two terminals (that is,
the quantity v2 - v1), multiplies this by the open loop
gain A, and causes the resulting voltage A(v2 - v1)
to appear at output terminal 3 as shown in Figure 4.
In an ideal op-amp,
the input impedance
is infinite, the output
impedance is zero
and the open loop
gain A is very large
and ideally infinite. In
practice,the open
loop gain is usually
greater than 100,000.
In order to control the gain of our circuit we use
feedback to close the loop around the op-amp as
shown in Figure 5. This circuit consists of an op-
amp and two resistors R1 and R2. Resistor R2 is
connected from the output terminal of the op-amp,
terminal 3, backto the negativeinput terminal,
terminal 1. We speak of R2 as applying negative
feedback; if R2 were connected between terminals
3and 2, we would call this positive feedback. Note
that R2 closes the loop from the output terminal
backaround to the input terminal of the op-amp. In
this circuit, the closed loop gain (G) of the op-amp,
from the input Vi to the output terminal, depends on
the ratio of R2 to R1.
For example, if R2 = 100 and R1 = 10, the gain G =
R2/R1 = 100/10 = 10. Thus, the output voltage V0
at terminal 3 would be equal to –10(Vi). The (–) sign
indicates that the output and input voltages are of
opposite polarity.
The TA-12/K-40 Temperature Adapter Kit is used in
conjunction with a digital multimeter to read
temperature. The Temperature Adapter consists of
three main sections: • Voltage Regulator
•Temperature Sensor
•Op-Amp
INTRODUCTION
THEORY OF OPERATION
Figure 1
Collector
Emitter
Base 2N3904 NPN
Transistor
Figure 2
2N3904 NPN
Transistor
Base and
Emitter
Junction
Figure 3
V+
V–
4
5
3
1
2
–
+
Figure 4
V+
V–
4
5
3
1
2
–
+
i1 = 0
A(V2 - V1)
+
–
V2
+
–
V1 i2 = 0
Figure 5
R2
1–
+V0 = –(R2/R1) Vi
or
V0 = – GVi
+
–
Vi R1 2+
–
3

-3-
Introduction
The most important factor in assembling your TA-12/K-40 Temperature Adapter Kit is good soldering techniques.
Using the proper soldering iron is of prime importance. A small pencil type soldering iron of 25 - 40 watts is
recommended. The tip of the iron must be kept clean at all times and well tinned.
Safety Procedures
• Wear eye protection when soldering.
•
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. Solder contains lead and is a toxic substance. Wash your hands
thoroughly after handling solder.
• Be sure that there is adequate ventilation present.
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 of 63/37 alloy.
DO NOT USE ACID CORE SOLDER!
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 flowonto the
lead as shown.
3. Allowthe 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
Agood solder connection should be bright, shiny,
smooth, and uniformly flowed over all surfaces.
Types of Poor Soldering Connections
Foil Side
Mount Part Bend Leads to
Hold Part
Solder and
Cut Off Leads

-4-
ASSEMBLE COMPONENTS TO THE PC BOARD
R2 - 10kΩTrim Pot
(see Figure A)
R5 - 1kΩ5% 1/4W Resistor
(brown-black-red-gold)
R10 - 3.9kΩ5% 1/4W Resistor
(orange-white-red-gold)
C1 - .01µF, 50V (103) Discap
U2 - MC7805 5V Regulator
(see Figure B)
R4 - 10kΩ5% 1/4W Resistor
(brown-black-orange-gold)
R8 - 10kΩTrim Pot
(see Figure A)
Figure A
Insertthe trim pot into the PC board
as shown. Solder and cut off excess
leads.
R3 - 47kΩ5% 1/4W Resistor
(yellow-violet-orange-gold)
R1 - 3.9kΩ5% 1/4W Resistor
(orange-white-red-gold)
U1 - IC Socket 8-pin
U1 - LM1458N Op-Amp IC
(see Figure C)
R6 - 1kΩ5% 1/4W Resistor
(brown-black-red-gold)
R9 - 10kΩ5% 1/4W Resistor
(brown-black-orange-gold)
R7 - 3.3kΩ5% 1/4W Resistor
(orange-orange-red-gold)
10kΩTrim Pot
PC Board
Figure C
Insertthe 8-pin IC socket into the PC
board in the direction shown. Solder
and cut off excess leads. Then, insert
the LM1458N op-amp IC into the
socket in the same direction shown.
Figure B
Insertthe regulator into the PC board
in the direction shown. Solder and cut
off excess leads.
MC7805
Regulator
PC Board
LM1458N
Op-Amp IC
PC Board
IC Socket
8-pin

-5-
FINAL ASSEMBLY
J3 - Battery Snap Red Wire
J4 - Battery Snap Black Wire
J2 - Black Multimeter Lead
(see Figure D)
J1 - Black Multimeter Lead
(see Figure D)
J6-Large Sensor Wire
J5 - Small Sensor Wire
(see Figure E)
Figure D
Pull the boot off of the alligator clip (to removeboot, clip
the alligator clip onto a pencil, then pull off boot). Insert
the wire (red wire for red boot, blackwire for black boot)
into the alligator clip as shown. Crimp the tabs over the
wire as shown and solder the wire to the clip. Cut off any
excess wire from the solder joint. Slide the boot back onto
the alligator clip.
Figure E
Prepare the ends of the 24” cable as shown in Step A
to the right. Verycarefully strip off 1” of casing on
both ends of the cable to expose the twowires inside.
Then strip the insulation off of both ends of the
insulated wire to expose 1/4” of bare wire. On one
end, cut the bare wire so that it is 1/4” long.
Solder the 2N3904 transistor to the end of the cable
wire with the 1” bare wire as shown in Step B to the
right. Slide the 1/2” section of #7 shrink tubing over
the bare wire. Solder the bare wire to the base (B)
and collector (C) leads of the transistor. Slide the #7
tubing over the solder joint. Put your hot soldering
iron or heat gun close to the tubing (do not touch the
tubing). The heat from your iron or heat gun will
shrink the tubing into place. Solder the insulated
wire to the emitter (E) transistor lead.
Slide the 1 1/2” section of 3/16” shrink tubing over the
transistor to cover the exposed wires as shown in
Step C to the right. Shrink the tubing in place with
your iron or heat gun.
Solder the other end of the cable to the PC board.
The insulated wire goes to point J6 and the bare wire
to point J5.
Red
Black
Boot
Alligator Clip Crimp Tabs
Solder
Step A
Step C
11/2” Section of
3/16” dia. Shrink Tubing
#7 Shrink
Tubing
2N3904
Transistor
(E)
(B) & (C)
Step B
Insulated
Wire
1/4”
1”
1/4”
Bare
Wire
1” 1/4”
Casing
0 1”
½”
¼” ¾”

-6-
CALIBRATION
1. Connect a 9V battery to the battery snap.
2. Connect the positive probe of your digital multimeter to point J1, and the negative probe to GND.
3. Adjust R2 for a reading of about 2.5 to 3V.
4. Then, connect the positive probe of the digital multimeter to J2 and the negative probe to J1.
5. Adjust R8 for the correct temperature reading on the digital multimeter. If you use the 2 volt range, you can
read the temperature to one tenth of a degree (that is, if the reading on the digital mulitmeter shows 0.733,
then you should read the temperature as 73.3OF).
COMPONENT CHECK
1. Recheck all of the values of the resistors, and make sure that they are placed in their exact location.
2. Be sure that the temperature sensor (2N3904) wire are soldered to their correct positions.
3. Be sure the notch of the op-amp (1458) is installed in the same direction as the marking on the PC board.
4. Be sure the regulator (7805) is mounted as instructed in the manual.
TROUBLESHOOTING
Contact Elenco®Electronics if you have any problems. DO NOT contact your place of purchase as they will not
be able to help you.
1. One of the most frequently occurring problems is poor solder connections. Tug slightly on all parts to make
sure that theyare indeed soldered.
2. All solder connections should be shiny. Resolder any that are not.
3. Solder should flow into a smooth puddle rather than a round ball. Resolder any connection that has formed
into a ball.
4. 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.
SCHEMATIC DIAGRAM

Elenco®Electronics, Inc.
150 Carpenter Avenue
Wheeling, IL 60090
[phone]
Website: www.elenco.com
e-mail: [e-mail]
QUIZ
Fill in the blanks and check your answers below.
Answers: 1. voltage regulator, temperature sensor, op-amp; 2. five; 3. collector, base, emitter; 4. collector, base;
5. 1mV, 1OF; 6. two, one; 7. negative; 8. single; 9. infinite, zero, infinite; 10. R8
1. The three main sections of the TA-12/K-40 are
________________, ________________, and
________________.
2. The output voltage of the LM7805 regulator is
_____ volts.
3. Name the three terminals of the transistor:
__________, __________, and __________.
4. The __________ and __________ leads of the
transistor are shorted together to make the
sensor.
5. At a constant current, the voltage across the base
to emitter junction decreases by approximately
______ for every______ increase in temperature.
6. The op-amp has ______ inputs terminals and
______ output terminal.
7. The TA-12/K-40 circuit uses __________
feedback to control the gain of the op-amp.
8. In the TA-12/K-40 circuit, a __________ supply is
used to power the op-amp.
9. In an ideal op-amp, the input impedance is
________, the output impedance is ________
and the open loop gain A is ideally ________.
10. You adjust trim pot ______ for the correct
temperature reading on the meter.