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QUASAR PROJECT KIT # 3073 - 12/24 HOUR GIANT CLOCK
do NOT fit through the holes of X4, X5 or X6 drilled
in 3073A PCB. The holes are meant as a placement
guide for soldering each connector. If you are
assemblying the kit alone use a piece of sticky tape to
hold the male connector vertical while the short pins
are seated in the holes. Just solder one pad and check
the connector is vertical. Make any correction needed.
Then solder the other pads.
Testing.
First check the bottom PCB, 3073B just by itself
unconnected to 3073A. Do not put in IC's. Plug in
12VDC plugpack. Use a multimeter to check that there
is +5V between both pins 4 & 14 and pin 5 of IC1. For
IC2 there should be 5V between pins 16 & 8 and
between pins 16 & 7. If these reading are correct,
disconnect the power,
Insert the ICs correctly orientated. Connect the two
boards together. Apply power. The display should light
up and show 12:00:00. The display is in 12-hour mode.
To select the 24-hour display press the hour switch as
you connect power.
Push the two switches to see how the hour and minutes
increase. Cover the LDR to test the dimming feature.
Press both switches to check you can access the adjust
mode. If you bought 4 batteries for battery backup (not
supplied with the kit) then connect the LK1 link to
allow the batteries to charge from the plugpack.
If it does not work. Solder bridges and components in
the wrong way are the most likely problems. Did you
put in all the links? If one or more display segments are
wrong trace back the display to the components driving
that display segment. Look for dry-joints.
Adjustment outside +/-255. If you find that you need
an adjustment outside the range of +/-255 then this
means that the crystal is out of specification. This can
be fixed within limits by changing the loading
capacitors. If the clock is running fast and the
adjustment value needs to be more than 255 then
increase the 27pF capacitors to 33pF (NPO type.) If it
is running slow and needs an adjustment to be more
than –255 (that is, -256, -260 etc) then decrease the
loading capacitors to 22pF or 18pF (NPO type.)
Changes in this Kit from Original Version. In the
hardware we have not allowed for two types of 2.3"
LED display pinout. We have used the pinout our LED
supplier makes for us (which is the variant pinout of
the article.) Connecting the two boards together has
been improved. In software, the author John Clarke
kindly corrected a rollover fault so that 23:59:59 went
to 0:00:00. 24 hour mode is the default start-up mode.
Support - email us at:
support@quasarelectronics.com
COMPONENTS
Tinned copper wire
Resistors 5%, 1/4W:
10R
R3
82R
R11 12 14 15 16 17 18
180R
R11
220R
R9 10 19 20 21 22 23
470R
R5 24 25 26 27 28 29 30 31
1K
R7
2K2
R2
4K7
R4
10K
R6
470K
R8
Zero ohm resistors for links on 3073b
2R2 1W R1
0.1 104 box poly MKT
1n5 box poly MKT
1N4004
1N4148
4.000MHZ
10uF/25V mini
100uF/16V mini
15V 1W zener diode
27p ceramic NPO type C7 C8
LDR
BC328
4051
PIC16F84
ULN2003A
7905
20 pin IC socket
18 pin IC socket
16 pin IC socket
0.05" Metal Pins
3mm x 6mm nut and bolt set
Metal spacer 3mm x 15mm
3mm screws x 6mm
2 pin SIL header
jumper
LED 0.56" display
LED 2.3" display
8 pin female header
8 pin male SIL strip
3073A PCB
3073B PCB
12"
C10
C9
D1 2 3 4
D5 D6
Xtal
C1 2 3 4 6
C5
ZD1
LDR
Q1 – Q8
IC2
IC1
IC3
IC4
1 set
1
7
1
7
9
1
1
1
1
1
4
1
1
1
4
2
1
5
1
1
2
1
8
1
1
1
1
1
1
2
8
4
8
1
1
2
4
3
3
1
1
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