ARRL ETP Solder 101 Instructions for use

ARRL ETP Solder 101 24-Hour Clock Kit Construction Manual
A Functional Approach
Parts Inventory
Cross-check the parts against this parts list. Note the resistor color codes,
especially the 10K (brn-blk-org) and 1K (brn-blk-red) resistors, which may
be difficult to tell apart. (Use good lighting and a magnifier.) Use care to
correctly identify the 78L05 voltage regulator, which is similar in
appearance to the 2N3906 transistors. The 0.1µF and 10pF capacitors may
also look very similar.
QTY Description
❒1 printed circuit board
❒1 PIC16C54 microcontroller [A]
❒1 18-pin DIP socket
❒1 78L05 voltage regulator [B]
❒4 2N3906 PNP transistor [C]
❒4 7-segment LED
❒11N914diode
❒1 4 MHz crystal
❒4 10pF capacitor (100) [D]
❒2 0.1µF capacitor (104) [E]
❒8 220 ohm 1/4 W resistor (red-red-brn)
❒3 750 ohm 1/4 W resistor (vio-grn-brn)
❒4 1K ohm 1/4 W resistor (brn-blk-red) [F]
❒4 10K ohm 1/4 W resistor (brn-blk-org) [G]
❒3 SPST pushbutton switch
❒1 3-AA cell battery holder
❒1 vertical power jack, 2.1x5.5 mm
❒1 2-56 1/2-inch screw
❒1 2-56 nut
B
A
C
D
E
F
G

Safety
•Apply power to the board only when instructed.
•Double-check part identification and polarity (if any) before soldering.
•Wear eye protection when soldering and
trimming component leads. Use care when
clipping off the excess leads because they
can flip up and cause eye injury. A good
technique is to hold the lead with your
fingers while you clip the lead off just at the
top of the volcano-shaped joint.
•Work in a well-lit, well-ventilated
workplace.
•Use an appropriate soldering iron and tip.
•Use only small-gauge rosin core solder.
Preparation (optional)
•The hole spacing of the resistors in this kit is 0.4 inches. If you have a
lead bending tool, you can pre-bend all of the resistor leads to this
spacing.
Clock PCB - Component Side
Clock PCB - Solder Side

Power Circuit
Locate the 1N914 diode. Note the banded end of the diode (the cathode).
Install the diode at the appropriate location, taking care to install it with the
banded end turned to match the band of the component outline. Mount the
diode flush with the surface of the board.
Install a 10K-ohm
resistor (brn-blk-org) at
the specified location
near the 78L05 voltage
regulator. All resistors
should mount flush with
the surface of the board.
Install the two 0.1µF
capacitors (104) at the
specified locations near
the 78L05 voltage
regulator. Don't force the
capacitors too close to the
board, but don’t leave them standing with long legs, either.
Solder all leads and clip off any excess.
Install the 78L05 voltage regulator. Don’t confuse
the voltage regulator with the 2N3906 transistors.
The voltage regulator and its outline on the board
both have a flat side — which should be aligned.
Push the voltage regulator into the holes until the
component body is about 1⁄8 inch above the
board surface. Tack solder the center lead,
straighten the component, then solder the outer
two leads.
Solder and clip off excess leads, inspect your
work, and touch up any solder joints.
Banded
End
Power circuit, showing orientation of diode.
78L05 voltage regulator

PIC Socket Installation
Locate the 18-pin IC socket. One end of the socket is marked with a notch.
The socket outline on the circuit board also has a notch. When you install
the socket, turn the socket so that the notches match up.
Hold the socket in place flush against the board and solder two opposite
corner pins.
The socket should be flush against the circuit board. If it isn’t, re-melt the
solder on the pins you tacked while pressing down on the socket with your
finger. When the socket is flush against the board, solder the remaining
pins of the socket. You will install the integrated circuit itself later.
Notch
Tack here…
…and here

Current Limiting Resistor Installation
Install eight 220-ohm resistors (red-red-brn) at the indicated locations, flush
against the circuit board. Solder and clip the excess leads.
Install four 1K-ohm resistors (brn-blk-red) at the indicated locations, flush
against the circuit board. Solder and clip the excess leads.
1K-ohm resistors
220-ohm resistors

Install three 750-ohm resistors (vio-grn-brn) at
the indicated locations, flush against the circuit
board. Solder and clip the excess leads.
Install three 10K-ohm resistors (brn-blk-org) at
the indicated locations, flush against the circuit
board. Solder and clip the excess leads.
You should have no resistors remaining.
Time-setting pushbutton switch installation
The time-setting pushbutton switches have four
pins. Turn the switches so the pins stick out on
the right and left of the switch and install them
in the indicated locations. If you have to force
the switches to get the pins into the circuit
board mounting holes, you might have the
switches oriented incorrectly.
Solder two pins at opposite
corners of each switch and
check that each switch is
flush against the board. If
not, re-melt the solder
while applying pressure on
the switch with your finger.
Once each switch is flush,
solder the remaining pins.
750-ohm resistors
10K-ohm resistors

Display 7-Segment LED installation
Locate the four 7-segment LEDs that
make up the time display. The pins on
the back of these LEDs are not
arranged symmetrically — this helps
you install the LEDs correctly. If you try
to force the LEDs in the wrong
direction, you can bend the pins and
damage the LEDs.
Notice that the 10s-minute digit on the
board is upside down. This allows the
decimal point of that LED to function
as the upper dot of the colon
separating the hour and minute digits
on the display. (Pretty clever, huh?)
Install four 7-segment LEDs as
indicated on the board (Remember,
the third LED from the left is installed
rotated 180° from the others!). Don’t
force the LED pins into the mounting
holes.
Mount the LEDs by tack soldering
opposite corner pins, as you did with
the IC socket. Press on each LED as
you heat the tacked pins to ensure the
LEDs are flush with the board.
When all four LEDs are flush and
straight, solder the remaining pins and
trim the excess pin lengths.
LED display 10s-minute digit.
Four LEDs soldered in place.
Pins on back of 7-segment LED.
Tack-soldered LEDs

Oscillator installation
Install the 4MHz crystal in the
indicated position. The orientation of
the crystal is not critical. Solder the
crystal flush with the board and clip
off excess leads.
Install the four 10pF capacitors in the
indicated locations. Solder and clip
off excess leads.
Switching transistor installation
Locate the four 2N3906 transistors.
Notice that they have a flat side, and
that the component outline also has a
flat side. Install the transistors in the
indicated locations so their flat sides
face the same direction as the flat
sides of the component outlines.
Carefully press down on the transistors
until they are approximately 1⁄8-inch above the
top of the circuit board.
Tack solder the center lead of each transistor,
straighten the transistor, and solder the outer
two leads. Solder and clip off excess leads.
!
~1/8-inch!
above top!
of board
Crystal oscillator and loading capacitors
2N3906 switching transistor locations.

Microcontroller Installation
You will now install the PIC 16C54
microcontroller. To align the pins of
the PIC with the holes in the socket,
turn the PIC over and gently bend the
pins on each side inward until they are
at a 90° angle with the bottom of the
PIC. (The edge of a table is a good
flat surface to press the legs against.)
The notch on one end of the PIC
indicates where pin 1 is located. The
IC socket also has a notch at one end,
as does the component outline on the
board. When you insert the PIC into
the socket, make sure the notches are
all pointing in the same direction.
Carefully place the PIC in position and
check the orientation of the pins
relative to the socket. Once you are
satisfied that the pins and socket line
up, press with both thumbs to rock the
PIC into the socket.
Once in place, inspect the PIC pins to
ensure that none got bent or crimped
under the IC or pushed outward away
and to the side of the socket.
Before
After
Bending PIC leads before insertion. (end view)

Power Connector
Installation
Locate the power
connector. The power
connector is installed
from the bottom, or
solder side of the
board. Install the
connector and hold it in
place against the work
surface while you tack
solder a single pin.
Check that the
connector is flush against the circuit board surface. If necessary, re-melt
the solder joint while applying light pressure to properly seat the connector.
When it is flush, completely solder the other two pins.
You do not need to completely fill the mounting holes of the power
connector, but be sure your solder wets both surfaces and forms a smooth,
shiny joint. (This is a very common point of failure for circuit boards.)
STOP HERE FOR DAY 1 - YOU WILL COMPLETE THE ASSEMBLY
AFTER INSPECTION BY THE QUALITY CONTROL DEPARTMENT.

Back-Up Battery Holder installation
Carefully bend the two leads on the back
of the battery holder out at a 90° angle,
and install the battery holder from the
solder (bottom) side of the circuit
board.
Before you solder the battery holder
leads, use the 2-56 screw and nut to
fasten the battery holder to the back of
the PCB. Do not over-tighten the nut, or
you may damage the screw, battery
holder, or both.
Solder and trim the battery holder leads
from the component (top) side of the
board.

Tests and operation
It’s now time to fire-up your completed
project. Install the wall wart barrel plug into
the power connector on the back of the
clock, then plug the wall wart into an
outlet. The digits of your clock should
illuminate and the center colon dots should
blink at 1-second intervals.
Press and hold the hour-set switch to
advance the hours digits. Release the
switch at the desired hour. Likewise, press
and hold the minute-set switch to set the
correct minutes.
To see the seconds, press and hold the
seconds display switch for as long as you
want to see the seconds displayed. Once
released, the time display returns to
normal hours and minutes format.
Final Set-up and Operation
Disconnect the wall wart from the outlet
and install 3-AA cells in the battery
holder. Install the batteries using the
correct polarities, as indicated in the
battery holder. The clock should start
operating on batteries, but the primary
source of power is the wall wart. The
display may be dimmer when operated off
the back-up batteries.
Once you reconnect the wall wart to a wall
outlet and set the proper time, your clock
project is ready to enjoy and show off to
your students and classroom visitors.
This completes construction of your 24-
hour digital clock.
Wall wart must be center pin positive,!
with a 9-12 VDC output.