Elenco Electronics K-11 Assembly And Instruction Manual
AC/DC POWER SUPPLY KIT
MODEL K-11
Assembly and Instruction Manual
Elenco®Electronics, Inc.
ight © 2004, 1989 b
yr
Cop
t of this book shall be reproduced b
No par
y Elenco
®
Electronics
y means;
y an
, Inc.
electronic
ights reser
All r
, photocopying, or otherwise without written permission from the publisher.
ved. Revised 2004 REV-J 753211
PARTS LIST
If you are a student, and any parts are missing or damaged, please see instructor or bookstore.
If you purchased this AC/DC power supply 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 #
1 R1 1kΩ 5% 1/4W brown-black-red-gold 141000
1 R3 2.7kΩ 5% 1/4W red-violet-red-gold 142700
1 R2 10kΩ Potentiometer 191516
CAPACITORS
Qty. Symbol Value Description Part #
1 C2 100µF Electrolytic 281045
1 C1 1000µF Electrolytic 291045
SEMICONDUCTORS
Qty. Symbol Value Description Part #
2 D1, D2
1 D3 1N5247 Zener Diode 315247
1 Q1 2N3904 Transistor 323904
1 Q2 2N6121 / HT1061
1N4001 Diode
Transistor
®
Electronics
314001
326121
MISCELLANEOUS
Qty. Symbol Description Part #
1 T1 Transformer YD-1485 440111
1 PC Board 518011
1 S1 Slide Switch 541009
1 Solder Roll
551124
1 Heat Sink 615002
1 Cable Clamp 1/4” 628750
3 Scre
w 6-32 x 5/16” 641641
3 Nut 6-32 644600
1 Line Cord 862100
1 Shrink Tubing 2” 890120
PARTS IDENTIFICATION
ransformer
Resistor Transistors
EBC
Diode
BCE
Cable
Clamp
Capacitor
Potentiometer
Switch
T
Heat Sink
Epoxy
Glass
Electrolytic
-1-
INTRODUCTION
The electrical power that is supplied by your power
company is what is known as Alternating Current or
AC. This current is constantly changing amplitude and
polarity (see Figure 1). The electrons (current) move
back and forth at a rate of 60 times per second. This
type of current is not suitable for most electronic
circuits. It must be converted into a Direct Current or
DC which moves in one direction only. Your MultiPurpose Power Supply does exactly that. It converts
THEORY OF OPERATION
A block diagram of the system is shown in Figure 2. It
consists of five basic circuits needed to convert 120
volts of AC to a usable 0-15 volts of DC. We will
analyze each circuit for a better understanding of
power supplies.
13VAC
Voltage
Stepdown
Voltage and
Current Control
0-15V
Output
Figure 2
VOLTAGE STEP-DOWN FUNCTION
In this circuit, 120 volts of AC is
reduced to two 13VAC out of
phase v
the rms (eff
peak voltage is really 18 v
This step-down is achieved by
the use of a transformer. The
winding of the transformer is
shown in Figure 3A and the
voltage across each winding is
shown in Figure 3B. In a
transformer, the magnetic field
produced b
current is induced into the
secondar
across the secondary winding is a ratio of the number
of turns between the primary and secondary winding.
If the r
voltage would be the same as the 120 volt input. In our
tr
secondary voltage will be 13 volts. If we were to put
an oscilloscope betw
secondary windings and looked at the other leads, we
would see that the two voltages are 180 degrees out
of phase
opposite directions from the common point. This is an
impor
see in the next section.
oltages. Thirteen v
ective) value. The
y the 120 v
y winding. The voltage
atio was 1:1 (equal turns), then the secondary
ansf
or
mer
, the r
atio is 120:13.
een the common lead of the two
This is because the windings are going in
.
er
tant point in con
v
Rectification
AC to DC
Filtering
Reference
Voltage
olts is
olts.
olts of
ting the A
DC
120VAC
AC Peak
AC Peak
Figure 3A
18V
–18V
Figure 3B
Therefore, the
C to DC as w
18V
–18V
36Vpp
36Vpp
e will
AC into DC. It also
allows you to vary the
amplitude of the
voltage from 0-15V
(0.25A - 12Vmax).
Also, your power
supply has an output
+168V
or
–168V
Time
336V
Peak to
Peak (PP)
or 120V
rms
of 8.5VAC, 0.5A
without regulation.
Figure 1
AC to DC CONVERSION - RECTIFICATION
This circuit that converts AC to
DC consists of two diodes D1
and D2. The purpose of a
diode is to pass current in only
one direction (see Figure 4). If
we were to take a battery and
connect it to a diode and lamp,
Direction of
Current Flow
Figure 4
as shown in Figure 5, the lamp would only light when
the diode is in the conduction direction. If we replace
the battery with a transformer secondary winding, the
diode will only conduct on the positive cycle of the
voltage as shown in Figure 6.
Note that the output of
the diode is a half-wave rectification with a hole in the
center. This voltage would be hard to filter out. It is
desirable to fill in this area. This is done by something
known as full wave rectification, which is using a
second winding out of phase with the first.
Battery
Diode
ot Lit
N
Lamp
Diode
Resistor
Figure 6
Diode
Battery
Lamp
Figure 5
Figure 7A shows the circuit for a full wave rectification.
Note that diode D1 conducts the previously described
and diode D2, one half cycle later. The diodes conduct
only when the voltage goes positive and no current
. The resulting output voltage
ws on the negativ
flo
e half
waveforms are shown in Figure 7B. Note that there is
no longer a gap betw
een cycles. This will make it
easier to filter the output voltage.
D1
Figure 7A
D2
Output D1
Figure 7B
Output D2
D1 & D2
-2-
Loading...