GEKCO CLK100 Supplement

GEKCO
DIGITALCLOCK
MODELCLK100
ASSEMBLY&OPERATIONMANUAL
GEKCO Inc.
1565 SW Cypress Ln
McMinnville, OR 97128
[phone] P/N595‐445REV1.1
Copyright 2021
GEKCO Inc.
All Rights Reserved
Printed in the United States of America
c

GEKCO DIGITAL CLOCK P/N CLK100 ASSEMBLY & OPERATION MANUAL
2 REV 1.1GEKCO INC.
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GEKCO DIGITAL CLOCK P/N CLK100 ASSEMBLY & OPERATION MANUAL
GEKCO INC. Rev 1.1 3
TABLE OF CONTENTS
1. INTRODUCTION ............................................................................................................................................... 5
2. OPERATIONAL SUMMARY .......................................................................................................................... 5
3. PARTS AND UNPACKING .............................................................................................................................. 6
3.1. TOP LEVEL PARTS LIST ...................................................................................................................................... 6
3.2. DISPLAY BOARD PARTS LIST ............................................................................................................................. 7
3.3. MAIN BOARD PARTS LIST .................................................................................................................................. 8
3.4. FINAL ASSEMBLY PARTS LIST ........................................................................................................................... 9
3.5. ENCLOSURE PARTS LIST ..................................................................................................................................... 9
4. ASSEMBLY NOTES......................................................................................................................................... 10
4.1. TOOLS ............................................................................................................................................................. 10
4.2. ASSEMBLY .................................................................................................................................................... 10
4.3. SOLDERING ................................................................................................................................................... 10
5. STEP-BY-STEP ASSEMBLY ......................................................................................................................... 11
5.1. DISPLAY CIRCUIT BOARD................................................................................................................................. 11
5.2. MAIN CIRCUIT BOARD ..................................................................................................................................... 15
6. INITIAL TESTS................................................................................................................................................. 17
7. FINAL TESTS .................................................................................................................................................... 18
8. IN CASE OF DIFFICULTY ............................................................................................................................ 18
9. FINAL ASSEMBLY .......................................................................................................................................... 18
10. OPERATIONAL INSTRUCTIONS .......................................................................................................... 21
10.1. SETTING THE TIME ............................................................................................................................................ 21
10.2. SETTING THE UTC MODE ON OR OFF ............................................................................................................. 21
10.3. SETTING THE UTC HOUR OFFSET.................................................................................................................... 21
10.4. SETTING THE ALARM TIME .............................................................................................................................. 22
10.5. SETTING THE ALARM ON OR OFF..................................................................................................................... 22
10.6. SETTING THE LOCAL TIME TO 12 OR 24 HOUR................................................................................................. 22
10.7. SETTING THE DISPLAY BRIGHTNESS ................................................................................................................ 22
11. THEORY OF OPERATION ....................................................................................................................... 24
11.1. BLOCK DIAGRAM.............................................................................................................................................. 24
11.2. MAIN BOARD CIRCUIT DESCRIPTION .............................................................................................................. 25
11.3. DISPLAY BOARD CIRCUIT DESCRIPTION.......................................................................................................... 25
12. FIRMWARE .................................................................................................................................................. 26
12.1. FLOW CHART .................................................................................................................................................... 26
12.2. FIRMWARE DESIGN DESCRIPTION.................................................................................................................... 26
12.2.1. Clock Mode.............................................................................................................................................. 26
13. PCA PICTORIAL DIAGRAMS ................................................................................................................. 27
13.1. MAIN BOARD .................................................................................................................................................... 27
13.2. DISPLAY BOARD ............................................................................................................................................... 28

GEKCO DIGITAL CLOCK P/N CLK100 ASSEMBLY & OPERATION MANUAL
4 REV 1.1GEKCO INC.
14. SCHEMATIC MAIN BOARD.................................................................................................................... 30
15. SCHEMATIC DISPLAY BOARD ............................................................................................................. 31
16. CUSTOMER SERVICE............................................................................................................................... 32
17. DOCUMENT REVISION HISTORY ....................................................................................................... 33
LIST OF FIGURES
FIGURE 1: DISPLAY BOARD TOP SIDE COMPLETED ASSEMBLY .................................................................................. 11
FIGURE 2: DISPLAY BOARD BOTTOM SIDE COMPLETED ASSEMBLY .......................................................................... 11
FIGURE 3DISPLAY BOARD BOTTOM SIDE .................................................................................................................... 12
FIGURE 4: DISPLAY BOARD TOP SIDE ASSEMBLY PICTORIAL ..................................................................................... 13
FIGURE 5: MAIN BOARD COMPLETED ASSEMBLY ....................................................................................................... 15
FIGURE 6MAIN BOARD TOP VIEW 1............................................................................................................................. 15
FIGURE 7: MAIN BOARD TOP VIEW 2 ........................................................................................................................... 15
FIGURE 8: MAIN BOARD TOP VIEW 3 ........................................................................................................................... 15
FIGURE 9: MAIN BOARD TOP VIEW 4 ........................................................................................................................... 16
FIGURE 10: MAIN BOARD BOTTOM VIEW .................................................................................................................... 16
FIGURE 11 RTC MODULE ASSEMBLY........................................................................................................................... 17
FIGURE 12: DISPLAY BOARD HARDWARE ASSEMBLY ................................................................................................. 18
FIGURE 13: DISPLAY BOARD TO MAIN BOARD ASSEMBLY ......................................................................................... 18
FIGURE 14: ENCLOSURE COVER TO BASE ASSEMBLY ................................................................................................. 19
FIGURE 15: FRONT PANEL ............................................................................................................................................. 19
FIGURE 16: FRONT PANEL TO BASE ASSEMBLY ........................................................................................................... 19
FIGURE 17: DISPLAY AND MAIN BOARD TO ENCLOSURE ASSEMBLY ......................................................................... 19
FIGURE 18 ENCLOSURE BACK ....................................................................................................................................... 20
FIGURE 19: MENU FLOW CHART................................................................................................................................... 23
FIGURE 20: BLOCK DIAGRAM ....................................................................................................................................... 24
FIGURE 21: SOFTWARE FLOWCHART ............................................................................................................................ 26
FIGURE 22: MAIN BOARD TOP ...................................................................................................................................... 27
FIGURE 23: MAIN BOARD BOTTOM .............................................................................................................................. 27
FIGURE 24 DISPLAY BOARD TOP SIDE .......................................................................................................................... 28
FIGURE 25 DISPLAY BOARD BOTTOM SIDE .................................................................................................................. 29

CLK100
GEKCO INC. Rev 1.1 5
1. Introduction
The Digital Clock Model CLK100 was designed to fill the need for an accurate digital clock with the
capabilities of two time zone displays in a compact format.
This clock has 6 digits for hours, minutes and seconds and the hours display can alternate between
two time zones, i.e. Coordinated Universal Time (UTC) and local time.
The CLK100 is offered in kit form or fully assembled and tested. The kit is easy to assemble with no
surface mount parts.
This step by step manual will guide you through the process to complete the assembly and testing of
the model CLK100 Digital Clock. The manual was designed so a total beginner in electronics can be
successful, but the more experienced builder can skip any unnecessary information. Also, this design
is fully open source for both the hardware and firmware. There are full schematics and pictorial
diagrams of the hardware, also there are links and flowcharts of the firmware microcontroller code.
2. Operational Summary
The Model CLK100 has 6 digits of seven segment displays to display HOURS, MINUTES and
SECONDS. The HOURS display can alternate between two time zones, which can be UTC and local
time. This function can be turned off by a menu selection if desired.
•The six digit display provides Hours, Minutes and Seconds
•Dual time zone display, alternates between two time zones every 2 seconds, i.e. UTC and
local
•The display LEDs are high contrast red, 0.56 inch character height
•Adjustable display brightness
•Local hours can be set for 12 or 24 hour mode
•Very accurate Real Time Clock (RTC) with battery backup
•Powered by a U.L. listed 5 VDC wall adapter
•Size: 4.16 x 2.35 x 3.5 inches (Width x Height x Depth)
•Weight: 0.75 pounds

GEKCO DIGITAL CLOCK P/N CLK100 ASSEMBLY & OPERATION MANUAL
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3. Parts and Unpacking
The kit is packaged in the order that the assembly is recommended. Each assembly block has an
associated parts bag. Only open a parts bag when called for during assembly to avoid misplacing parts.
3.1. Top Level Parts List
Remove the parts from the main bag and separate each individual parts bags.
ITEM
QTY
PART NO.
DESCRIPTION
1
1
DBR100-KIT
Clock Display Board PCA parts bag
2
1
CLK100M-KIT
Clock Main Board PCA parts bag
3
1
2217625
Real Time Clock (RTC) Module DS3231
4
1
CLK100HDW-KIT
Final Assembly Hardware
5
1
CLK100ENC-KIT
Enclosure with Front and Back Panels
6
1
54-660
AC to DC Power Supply Wall Adapter Single
Output 5 Volt 1 Amp 5 Watt 2.1mm Conn

DIGITAL CLOCK MODEL CLK100
GEKCO INC. Rev 1.1 7
3.2. Display Board Parts List
Clock 100 Display Board Printed Circuit Assembly (PCA) parts kit, P/N DBR100-KIT
ITEM
QTY
REFDES
PART NO.
DESCRIPTION
1
3
DS1,DS2,DS3
412-499
LED Display Module 7-Segment 2-Digit 0.56"
2
1
X1
434-3110
Socket IC Dip24-300
3
1
U1
442-3090
IC LED Display Driver MAX7219CNG
4
1
J1
131-1X10
Connector Header Single Row Male 10 pins
5
2
LED1,LED2
412-125
LED Red PCB Mount T1 3/4
6
1
C2
26-102
Cap elect alum radial lead 10uF/16v
7
1
C1
20-104
Cap mono Cer 50v radial lead
8
1
R1
6-1002-12
Res metal film 1/4w 1% 10k
9
1
81-180911D
PCB Display Board
1
2 3 8
6
5
7
4
3

GEKCO DIGITAL CLOCK P/N CLK100 ASSEMBLY & OPERATION MANUAL
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3.3. Main Board Parts List
Clock 100 Main Board PCA parts kit, CLK100M-KIT
ITEM
QTY
REFDES
PART NO.
DESCRIPTION
VALUE
1
3
C3,C4,C5
20-104
Cap mono Cer 50v radial lead
0.1UF
2
2
C1,C2
21-220
Cap mono Cer COG radial
lead
22pF 100v
3
1
C6
26-102
Cap elect alum radial lead
10uF/16v
4
1
Y1
404-160
Crystal HC49
16.00 MHz
5
1
D1
55-62
Diode schottky rectifier
1N5817-T
6
3
SW1,SW2,S
W3
64-1839
Switch Momentary SPST
7
1
SW4
64-1827
Switch Momentary 5mm H
8
1
J4
131-1X10S
Conn Header Female Single
Row 10 pins
9
1
J2
131-1X06RA
Conn Header Right Angle
Male 1 row of 6
pins
10
1
J3
131-1X05
Connector Header
Male 1 row of 5
pins
11
1
J1
134-002
Connector Power 2.1mm PCB
Mount
12
1
RN1
95-103
Res network 6 sip
10K 5 Res SIP
Package
13
1
X1
434-311
Socket IC
Dip28-300
14
1
U1
444-106-01
IC Microcontroller
Programmed
Part CLK100
V1.01
15
1
LS1
220-1420
Audio Piezo Transducer 30V
16
1
81-181004A
Printed Circuit Board
Main Board
1
2
16
3
4
5
6
7
13
14
8910
12
11
15

DIGITAL CLOCK MODEL CLK100
GEKCO INC. Rev 1.1 9
3.4. Final Assembly Parts List
Clock 100 Final Assembly Hardware parts kit, P/N CLK100HDW-KIT
ITEM
QTY
PART NO.
DESCRIPTION
1
2
258-616
Hardware Angle Bracket 4-40
2
2
250-1418
Hardware Screw Panhead 4-40 x 1/4”
3
2
250-1533
Hardware Screw Panhead 4-40 x 1/8”
4
2
252-440
Hardware Nut 4-40
3.5. Enclosure Parts List
Clock 100 Enclosure kit, P/N CLK100ENC-KIT
ITEM
QTY
PART NO.
DESCRIPTION
1
1
86-20113001
Enclosure Base
2
1
86-20113002
Enclosure Cover
3
2
86-20113003
Enclosure Bezel
4
1
86-181114F-A
Enclosure Front Panel
5
1
86-181114F-A
Enclosure Rear Panel
6
1
250-1410
Hardware Screw Flat-head 4-40 x 3/8”

GEKCO DIGITAL CLOCK P/N CLK100 ASSEMBLY & OPERATION MANUAL
10 REV 1.1GEKCO INC.
4. Assembly Notes
4.1. TOOLS
You will need these tools to assemble your kit.
•Diagonal Cutters
•Needle Nose Pliers
•Flat Head Screwdriver
•Philips Screwdriver (for the enclosure
only)
•Pencil Soldering Iron (22 to 25
WATTS)
4.2. ASSEMBLY
1. Follow the instructions carefully. Read the
entire step before you perform each
operation.
2. Refer to the Pictorial and Detail
Illustrations for help in performing the
assembly steps. The illustrations are
arranged in the proper sequence, as called
for in the assembly steps.
3. Pictorials show the overall operation for a
group of assembly steps: Details generally
illustrate a single step. When you are
directed to refer to a certain Pictorial “for
the following steps,” continue using that
Pictorial until you are referred to another
Pictorial for another group of steps.
4. Position all parts as shown in the
Pictorials.
5. Solder instructions are generally given only
at the end of a series of similar steps. You
may solder more often if you desire.
6. Each circuit part in an electronic kit has its
own reference designator (R3, C8, etc.).
Use these designators when you want to
identify the same part in the various
sections of the manual.
7. SAFETY WARNING: Avoid eye injury
when you cut off excessive lead
lengths. Wear safety glasses or
goggles and hold the leads so they
cannot fly toward your eyes.
4.3. SOLDERING
Soldering is one of the most important
operations you will perform while assembling
your kit. A good solder connection will form an
electrical connection between two parts such
as a component lead and a circuit board foil. A
bad solder connection could prevent an
otherwise well-assembled kit from operating
properly.
It is easy to make a good solder connection if
you follow a few simple rules:
Use the right type of soldering iron. A 22 to 25-
watt pencil soldering iron with a 1/8” or 3/16”
chisel or pyramid tip works best.
Keep the soldering iron tip clean. Wipe it often
on a wet sponge or cloth: then apply solder to
the tip to give the entire tip a wet look. This
process is called tinning, and it will protect the
tip and enable you to make good connections.
When solder tends to “ball” or does not stick to
the tip, the tip needs to be cleaned and re-
tinned.
NOTE: What solder to use, leaded or lead
free? The printed circuit boards in this kit are
plated with lead free solder so if you choose to
use lead free solder the complete assembly will
be RoHS compliant. Regarding kits though, it is
more difficult to solder with lead free material
due to the higher melting temperature, so we
recommend using a rosin core, radio-type
solder (60/40) or (63/37) tin-lead content) for all
of the soldering in this kit. If you decide to use
leaded solder, be careful to wash your hands
after soldering and never eat, drink or smoke,
until you wash thoroughly and you are done
soldering. Contain all materials that touched
leaded solder in a special container dedicated
for that purpose. This waste can be disposed
of at electronic-recycling events or contact your
waste management company