Arduino IN-14 Nixie User manual

Arduino IN-14 Nixie Clock v42
“All-In-One” Clock
Operating Instructions
&
Construction Manual
NixieClockIN14InstructionManualRev2V42

Contact In ormation
If you want to get in contact with us, please e ail to:
nixie@proton ail.ch
We'll usually get back to you right away. We can help you with kits or construction.
We also offer discounts for direct purchases, we save the Ebay fees, and share this with you.
http://www.open-rate.co /Store.ht l
So tware
The software is open source and is available on GitHub at the address:
https://github.co /isparkes/ArdunixNix6/releases
This board works with Release “Revision 4 boards” under the “Releases” tab.
Troubleshooting
If everything does not work as you expect, please carefully look at the tests in the construction steps, and
the troubleshooting tips.
At the end of the anual, there is a troubleshooting section, which goes through so e of the co on
proble s. If you can't work it out, please get in contact with us. We guarantee that you will get going.

Description
The Arduino Nixie Clock is a beautiful ix of old and new, resulting in a high accuracy, low power clock
which will be a talking point in your ho e.
The clock has the following features:
•Latest technology, highly reliable and accurate.
•Tried and tested design, with any hundreds of clocks sold.
•Based on the Arduino icro-controller: Easy to progra an well docu ented.
•Open source hardware and software. Nothing is hidden in this clock. (You ay odify and load the
software).
•Low power consu ption.
•Long tube life: Anti Cathode Poisoning (ACP) and configurable blanking akes sure that the tubes
will stay healthy for any years with no intervention fro you.
•The ultiplexed display and auto atic di ing used in this design extends the life of the tubes
indefinitely. So e other designs run the tubes too “hard”, and this causes a rapid degradation in
the useful life of the tube.
•All settings are stored in non-volatile e ory. Once they are set, they are re e bered forever, or
until you change the again.
•RGB back lighting allows you to set the the color of the back lighting to practically any color you
desire.
•A bient light sensing, with auto atic tube di ing, which sets the tube and LED brightness
according to the light conditions. This also increases tube life.
•Absolutely silent operation. So e Nixie clocks e it an irritating “buzz” or “hiss” which is especially
annoying if you keep the clock in a bedroo .
•Auto atic week day or weekend blanking, extends the life of tubes even further
•Auto atic ti e of day blanking, can blank between a start hour and an end hour, on week days,
weekends or every day
•Configurable suppression of Anti Cathode Poisoning when the clock is fully di ed. In the iddle
of the night, all the digits lighting up at full brightness could be disturbing. You can choose to stop
ACP when the clock is fully di ed
•The High Voltage Generator auto-calibrates itself to atch your tubes and power supply, eaning
that the power consu ption is the lowest possible. (Usually 2W when fully bright, 0.4W when
blanked).
•Highly accurate when using RTC odule:
•Battery backed, te perature co pensated, high accuracy clock. The accuracy is Accuracy
±2pp fro 0°C to +40°C. (Maxi u 1 inute per year).
•The battery life should be 3 years in nor al use.
•Retains the date and ti e even when turned off (not just for a few inutes, but for as long
as the battery lasts)
•Leap Year Co pensation Valid Up to the year 2100
•Extre ely accurate when using the optional Wifi odule:
•The ti e never drifts, is always right to within 1 second.
•Auto atically co pensates for Daylight Savings Ti e changes, leap years and seconds.

General
The clock has different odes of operation, which you select using the pushbutton. When you start the
clock up th very first ti e, it will start in “Ti e Display Mode”. We set it up to be the right ti e for where
the clock is being shipped to, so in the best case you will not even need to set the clock the first ti e!
The other odes of operation are described in the following sections.
Sa ety
The voltages produced in the High Voltage circuit can reach peaks of 400V! Take precautions not to
electrocute yourself! If you are not sure what this eans, please do not use this clock and return it for a
full refund.
A shock fro the clock high voltage circuit is at least a nasty bite. At worst it can kill you.
We decline any responsibility in the case of injury or death.
REPEAT: If you are not sure, please do not use the clock.
Powering Up
When you power the unit up, it will display “88:88:88” for several seconds. This is for the calibration of the
High Voltage Generator to atch the power adapter you have attached. During this ti e you ight hear
so e faint crackling noises fro the generator. This is nor al.
After finishing the calibration, the version nu ber (“00:42:07”) will be displayed for about a second. The
clock will then go into nor al operating ode.
Time Providers
Real Time Clock (standard)
By default, the clock co es with a Real Ti e Clock (RTC) odule which provides a battery backed ti e
source that re e bers the ti e even when the clock is not powered up.
WiFi Time Providers (optional)
More up to date is a WiFi real ti e provider, which logs into your ho e WiFi network and periodically
retrieves the ti e fro Internet ti e sources. These are accurate to 1 second, and auto adjust for Daylight
Savings Ti e. You configure once, and then the odule re e bers the configuration forever.
Additionally, the WiFi ti e odule gives you a easy to configure interface, which you can use to set up the
clock using a tablet, phone or co puter.

Time Display Mode
Nor ally, the clock will show the ti e. To show additional infor ation press the button with a “short”
press. Each press cycles through the following infor ation. After 5 seconds, the display will revert to the
nor al ti e display.
Mode Description Values
Date Date. The current date will be shown.
Te p Temperature. The current internal te perature inside the clock
case will be shown in degrees Celsius. If this goes above 40, you
should consider ventilating the case, because the te perature
co pensation is not able to work at such high voltages, and the
clock life ay be reduced, and the ti e ay drift.
Light Ambient Light Reading. This shows the current a bient light
reading fro the LDR (light dependent resistor). It is a nor alized
value, and goes between 100 (dark) to 999 (bright). This controls the
di ing of the tubes.
100: darkest
999: brightest
Version Display the version nu ber. The for at will be :”VV vv 07”, where
ajor version is “VV”, inor version is “vv” and the “21” is the id for
the version display.
00:42:07
Setting Mode
To enter setting ode, press the button for ore than 1 second (“ ediu press”). The “RGB back light”
LEDs will start to flash white. The nu ber of consecutive flashes indicates the ode you are in.
Each ediu press of ore than 1 second will ove the setting ode onto the next. When you finish the
setting odes, the clock returns to nor al ti e display ode.
To exit the setting ode before going through all the options, press the button for ore than 2 seconds
(“long press”). The “RGB back light” LEDs will return back to their nor al operation. Another way of exiting
is to cycle through all of the setting options, after which you will return to ti e ode.
To change a setting, press the button for less than one second, and then release it (“short press”).

Mode Description Values
Time mode. This is the nor al ode and displays the ti e. It is the
nor al start up ode of the clock. If you do nothing. The clock is in
this ode.
In this ode a short press cycles through the values given in “Ti e
Display Mode”, but always returns to the standard ti e display after
5 seconds.
Time and Date Settings
Set minutes. Each short press will advance the inute. The
inutes roll over back to 0 ffter reaching 59 inutes. Each ti e you
set the inute, the seconds is reset to 0.
Set Hours. Each short press will advance the hour. The hours roll
over back to zero after reaching 12 or 24 (depending on the 12/24
hours ode).
Set Day. Each short press will advance the day. The day roll over
back to one after reaching the axi u nu ber of days in the
onth.
Set Month. Each short press will advance the onth. The onth
roll over back to zero after reaching 12.
Set Year. Each short press will advance the year. The year roll over
back to 2015 after reaching 2099.
Basic Settings
“00”
flashing
12 or 24 hour time. The hours are displayed in 12 or 24 hour
ode.
“1” = 12 hour
“0” = 24 hour
default: 0
“01”
flashing
Blank leading “0”. Blank out the leading “0” fro single digit hours. “1” = blank
“0” = don't blank
default: 0
“02”
flashing
Scroll back. Use the scroll back (rapid count down) effect when
changing fro “9” to “0”.
“1” = enable
“0” = disable
default: 1
“03”
flashing
Date ormat. Set the for at that the date is displayed in. “0” = YY.MM.DD
“1” = MM.DD.YY
“2” = DD.MM.YY
default: 2
“04”
flashing
Display blanking. To preserve the tubes, you can set the display to
be blanked.
Options:
•“4” = “hours”: Blanks between the start and end hour every
day.
•“5” = “H or weekends”: This blanks all day during the
weekends and between the start and end hour every other
day.
•“6” = “H or week days”: This blanks all day during the week
days and between the start and end hour every other day.
•“7” = “H on weekends”: This blanks between the start and
end hour on weekends.
•“8” = “H on week days”: This blanks between the start and
end hour on week days.
“0” = Don't blank
“1” = Weekends
“2” = Week days
“3” = Always
“4” = Hours
“5” = H or weekends
“6” = H or week days
“7” = H on weekends
“8” = H on week days
default: 0
“05”
flashing
Blanking Hour Start. Hour blanking will start at this hour, on the
days set by the Display Blanking Mode. If the display blanking ode
does not use hours, this setting is not shown.
Default: 00

“06”
flashing
Blanking Hour End. Hour blanking will end at this hour, on the
days set by the Display Blanking Mode. If the display blanking ode
does not use hours, this setting is not shown.
Default: 07
“07”
flashing
Anti Cathode Poisoning night suppression. The ACP which runs
during the night lights the digits up at full brightness, and so e
people ight find this disturbing. Using this setting, you can stop
ACP happening when the display is fully di ed (e.g. at night).
“1” = don't do ACP
when di ed
“0” = do ACP always
default: 0
Special E ects Settings
“08”
flashing
Fade Speed Slower. Each short press will ake the fade speed
between digits slower.
Default: 50
Max: 200
Min: 20
“09”
flashing
Fade Speed Faster. Each short press will ake the fade speed
between digits faster.
Default: 50
Max: 200
Min: 20
“10”
flashing
Scroll-back Speed Slower. Each short press will ake the “scroll-
back” speed slower.
Default: 4
Max: 40
Min: 1
“11”
flashing
Scroll-back Speed Faster. Each short press will ake the “scroll-
back” speed faster.
Default: 4
Max: 40
Min: 1
Back Light Settings
“12”
flashing
Back Light Mode. This sets the ode of the back light.
“Fixed” ode will show the back light color according to the Red,
Green and Blue channel intensities.
“Pulse” will ake the intensity of the back light “pulse”, brightening
for a second and then darkening for a second, but always
respecting the relative intensities set by the Red, Green and Blue
channel intensities.
“Cycle” fades the back lighting rando ly, and does not use the Red,
Green and Blue channel intensities. These settings will be skipped if
cycle ode is selected.
Options “0”, “1” and “2”, do not di with the bulbs. Options “3”, “4”
and “5” do.
“0” = Fixed
“1” = Pulse
“2” = Cycle
“3” = Fixed/Di
“4” = Pulse/Di
“5” = Cycle/Di
default: 0
“13”
flashing
Red Channel Intensity. Sets the axi u intensity of the red
channel back light. This will be di ed according to the display
di ing. If you are in cycle ode, this setting will be skipped.
Default: 15
Max: 15
Min: 0
“14”
flashing
Green Channel Intensity. Sets the axi u intensity of the green
channel back light. This will be di ed according to the display
di ing. If you are in cycle ode, this setting will be skipped.
Default: 15
Max: 15
Min: 0
“15”
flashing
Blue Channel Intensity. Sets the axi u intensity of the blue
channel back light. This will be di ed according to the display
di ing. If you are in cycle ode, this setting will be skipped.
Default: 15
Max: 15
Min: 0
“16”
flashing
Cycle Speed. If you are in cycle ode, this controls the speed at
which the colors cycle. The higher the nu ber, the slower the
colors will change.
Default: 10
Max: 64
Min: 4
HV Generation Settings (See “HV Settings” note)
“17”
flashing
HV Target Voltage Higher. Each press sets the HV target voltage
higher by 5V.
Default: 180
Max: 200
Min: 150

“18”
flashing
HV Target Voltage Lower. Each press sets the HV target voltage
lower by 5V.
Default: 180
Max: 200
Min: 150
“19”
flashing
PWM On Time Longer. This setting controls how long the PWM On
pulse is. Nor ally you should not have to change this, but you can
try changing this is the HV generation is noisy or you have unusual
tubes.
Default: 150
Max: 50
Min: 500
“20”
flashing
PWM On Time Shorter. This setting controls how long the PWM On
pulse is. Nor ally you should not have to change this, but you can
try changing this is the HV generation is noisy or you have unusual
tubes.
Default: 150
Max: 50
Min: 500
In ormation Settings
“21”
flashing
Current case temperature. Show the current te perature inside
the case (used as part of the te perature co pensation for the
clock crystal).
“22”
flashing
Clock version. Show the clock software version.
Digit Test. Will roll through all digits on all locations to check that
the display is healthy.
Note “HV Settings”: Before leaving the clock for long periods with a new “HV Generation” setting, check
that neither the MOSFET nor the 7805 voltage regulator is running too hot. If either of these co ponents
gets too hot, either adjust the high voltage settings or add a heat sink.

Display Blanking Mode
During display blanking ode the tubes will be off depending on the display blanking settings, but the LEDs
will continue to work as usual, telling you that the clock is still running.
You can configure the display to blank at weekends, during week days, always or never (the default). Also
you are able to define hours during which to blank. For exa ple I have a setting saying that the clock is
blanked on weekdays between 7a and 4 p , while I a out at work. At weekends, the display runs all the
ti e.
You are also able to override the blanking. Press the button while the clock is blanked, and the display will
co e on again. Pressing the button will display the ti e for about a inute (60 seconds, but the display is
only blanked on the inute change).
If you press the button ultiple ti es within 5 seconds, the blanking will stay off for longer periods:
•1 Press: 60 seconds
•2 Presses: 1 hour
•3 Presses: 4 hours
Tube Healing Mode
After a long period of ti e, tube fila ents which are not often used (e.g. the “9” on the tens of hours or
inutes) can get di , despite the ACP that is regularly done.
If you ake a “super-long” press of the button ( ore than 8 seconds), the clock will enter fila ent healing
ode. All the power will be placed through a single fila ent of a single digit to clean it. A short press will
change the selected fila ent. Another super-long press or cycling through all the fila ents will return the
clock to nor al.
Warning!
Caution! Don't leave a single fila ent in this state for an extended period of ti e. It is a
harsh process, and ay da age the tube if you leave it in this ode for too long.
Nor ally a few inutes will restore the cathode digit.
Warning!
Be care ul using tube healing mode!
It is an extre ely harsh process, and should only be used if you see dark spots or
“shadows” on digit fila ents. Nor ally, the ACP should take care of your tubes and only
in exceptional cases do you “need tube healing”.
Factory Reset
To reset the clock back to initial settings, hold down the button while powering on. The “tick” LED will flash
10 ti es to signal that the reset has been done.
Everything will be reset back to the factory default state.
External power supply
The perfect voltage for the external power supply is 7.5V or 9V DC. You can use 12V DC. If you use ore
than 12V be aware that you ight have to provide a heat sink for the power co ponents and adjust the HV
voltage generation. It is not advised to use ore than 12V.
The absolute axi u per issible is 24V DC. Higher voltages than this will surely da age the clock.

Board layout
For reference, the board layout is as shown (viewed fro the top):
The connections are:
Connector Description Values
POWER External power should be applied to the board with this connector.
Any DC input source is possible, fro 7.5V – 12V. Higher voltages
ay be possible, but could cause the digits to flicker if the voltage is
too high, and you ight have to provide a heat sink for the the
MOSFET and voltage regulator.
The absolute axi u input voltage is 24V. Any higher voltage
than this will da age the board within a few seconds!
The input VIN is protected against the input being connected
reversed.
The input current ranges fro 300 A to 1A depending on the size
of the tubes and the nu ber of LEDs you are driving.
170V: Output of high voltage for driving external neons etc.
GND: The negative side of the input supply
VIN: The positive side of the input supply
VCC: Output of regulated 5V, which can be used to drive auxiliary
circuitry.
FRONT These are the controls that go on the front panel: The input button
and the Light Dependent Resistor to detect a bient light.
GND: The “ground”. One lead of the button and one lead of the LDR
and one lead of the button are connected to this.
BTN1: The other lead of the button is connected to this input
DLS: “Di ing LDR Sense”: The other lead of the LDR is connected
to this
VCC: Regulated 5V output to drive any LEDs or lighting. Note that
you can also connect the LEDs to the VIN if you want to reduce the
load of the regulator.
RTC / WIFI The connection for the RTC (Real Ti e Clock) or WiFi ti e provider
odule. Connect this to the appropriately arked ter inals on the
RTC / WIFI odule.

Schematic
Below is the sche atic for the clock.

Construction
Preparation:
You should have a s all tipped soldering iron, so e thin (< 1 , ideally 0.6 ) solder, and electronic
side cutters.
Components:
You should find the following contents as listed in the BOM (Bill of Materials). It is best to check the
contents before you start.
Please see the appendix to help you identify individual co ponents.
Low Voltage Circuit:
Parts List:
D1 IN4001
C2 100nF
C3 220uF
C4 220uF
IC1 7805TV
R14 3k
LED1 LED3MM
SV1 CONN_POWER
The Low Voltage circuit is a very traditional voltage regulator using a linear regulator. It's job is to reduce
the external voltage fro the power adapter down to a known and stable 5V to drive the icro-controller
and the 74141/K155ID.
Put the parts on the board in the arked locations in the order they appear on the list.
Notes:
•See the section on “Co ponent Identification” for help with identifying the co ponents.
•D1 and D2 look very si ilar, but have different jobs to do. Be careful to get the 1N4001 and not the
UF4007.
•D1 should be placed so that the white stripe on the body lines up with the white stripe on the
board.
•C3 and C4 ust go the right way round. The negative side is arked with a stripe. (See hint)
•The LED ust go with the right polarity. The side which has the shorter lead goes nearest the
diode. (See hint)
•Put IC1 so that the etal tab lines up with the white stripe on the board. The etal side faces to
the outside of the board.

Test Step
Once all the co ponents are on the board, hook up the power, and check that the power
LED co es on.
Check also that the voltage is 5V between the “GND” test point and the “VCC” test point
and at the power connector.
Trouble
shooting
If the LED does not co e on, turn off i ediately to avoid da age to the co ponents.
Check your soldering and the polarity of the co ponents.
If the co ponents are in the right way, connect the power again, and check that the 7805
voltage regulator does not get hot. If it does not, easure the voltages in the low voltage
circuit.
Measure the voltage at the input (“Vin”) and at the cathode side of D1 (nearest the centre
of the board). This should easure 0.7V less than the input voltage.
If all is well, proceed to the next step. If not, check carefully the orientation of the co ponents and the
power leads. Diode D1 protects the board fro having the power connected inverted.
If the LED co es on, check for a few seconds that the 7805 does not heat up. It should stay al ost cold.
Hint: The 220 uF capacitor
The electrolytic capacitor has a stripe on
it to denote the negative side of the
capacitor. The positive side of the
capacitor (which goes into the “+” on the
board) is the other one!
Hint: The LED orientation
The LED has one lead longer than the
other, and a flat on one side. The side
with the shorter lead (the cathode) goes
into the hole on the board nearest the
diode.
The LED should look so ething like this:
The LED

At the end of the low voltage circuit build, your board should look like this:
Low Voltage CircuitLow Voltage Circuit
Low Voltage Circuit

High Voltage Circuit:
Parts List:
C5 22pF
C6 22pF
C1 2.2uF 400V
C7 100nF
C8 100nF
D2 UF4007
S28 SOCKET 28
Q2 16MHz
L1 100uH
R10 3k
Q1 IRF840
R1 390k
R2 4.7k
R30 10k
IC3 MEGA8-P
The high voltage circuit uses the icro-controller to drive the boost circuit with a high frequency square
wave, and has a feedback loop in which the controller reads the voltage produced via an analogue input,
and regulates the brightness of the tubes so that there is no flickering or unwanted di ing.
Notes:
•See the section on “Co ponent Identification” for help with identifying the co ponents.
•C1 ust go the right way round. The negative side is arked with a stripe (see hint).
•Put Q1 so that the etal portion lines up with the white stripe on the board. The etal side faces
to the outside of the board.
•D2 should be placed so that the white stripe on the body lines up with the white stripe on the
board.
•Put the icro-controller socket in first and solder it. Make sure that the depression on the end of
the socket lines up with the arking on the board. When you put the chip in, the chip should go in
with the depression atching the silk screen on the board.
Warning!
Double check the orientation/location o the components be ore you proceed!
Especially check that R1 and R2 are in the right positions, and that the electrolytic
capacitor C1 is the right way round. If you switch R1 and R2, you will put 170V into the
icro-controller, and this will destroy it.

Once all the co ponents are on the board, hook up the power. Give your work a careful check to ake
sure that the orientation of the co ponents is right. Especially check that the stripe on C1 is facing the
arking on the board.
Warning!
Be care ul, we are dealing with high voltages now!
The voltage ay be significantly higher than 170V at the o ent, because the high
voltage generator is powerful and the output is not loaded. Once you add a load, (by
connecting the tubes), the voltage should oscillate around 170V – 190V, and ight have a
slight “sawtooth” appearance if you view it with an oscilloscope.
Test Step
Apply power to the board again. Listen for any stressed sounding buzzing or hu ing,
and check that neither the 7805 nor the MOSFET get excessively hot.
Check that the power LED still lights.
Trouble
shooting
I you hear any angry sounding buzzing turn the power o immediately and check
the orientation o C1! The circuit should run al ost silently, with only a very faint
“crackling” sound.
If you can't reach the target voltage, turn off and check the polarity of your co ponents,
especially C1. If you have an oscilloscope, you can check the voltage at the gate of the
MOSFET, and it should show pulses of high frequency square wave: this is the driver
wavefor to the HV generator, which is being turned off and on by the voltage detection,
trying to achieve the target voltage (180V default).
Warning!
Note also that the “Power” header also has high voltage exposed on it!
This is for if you want to drive neons instead of LEDs for the colons. Be careful handling
the board, it is easy to touch the “Power” header by istake. If you are sure you won't be
needing it, you can snap the extra pin off and populate only the botto 3 pins on the
connector.
Test Step
Check the voltage at the 170V test point. You should read a voltage in excess of 170V.
You can also test using an old neon la p if you have one. Te porarily connect the neon
la p between the “GND” test point and the “170V” test point with an appropriate ballast
resistor (turn the power off first). Turn the power on and the neon la p should co e on.
Trouble
shooting
Q1 can get war , but should not get too hot to touch. If it gets hot, you need to check
the orientation of the co ponents and that there are no solder bridges.
I you don't get the expected voltage reading:
•Check your soldering that there are no bridges or dry joints.
•Check that the external power supply is able to supply the power needed to
achieve the high voltage: check that the VIN voltage is stable and not fluctuating.
•Te porarily connect the LDR and re-test.
•Te porarily connect the button and do a factory reset

Hint: Mounting the 28 pin socket
Mounting the 28 pin socket can be a little
difficult. A good trick is to fix it in place
with a s all piece of tape, and the solder
one leg in place. You can hold the socket
fir while you “wet” the solder again,
which will hold the socket fir ly enough
to solder the re aining pins. One leg is
usually enough to hold the socket in place
while you solder the others.
At the end of the high voltage circuit build, your board should look like this:
Mounting 28 pin socket
High Voltage Circuit

LEDs/neons
Parts List:
RTC RTC (see note)
WiFi WiFi Module (see note)
SV3 CONN_RTC (see note)
R37 1k
R38 1k or 120k (see note)
R39 1k or 120k (see note)
Q3,Q4,Q5 2N7000
Q6 MPSA42
LED8/NEON1 LED 5 or neon (see note)
LED9/NEON2 LED 5 (see note)
Neon1 Neon indicator la p
Neon2 Neon indicator la p
R17 10k
R9,R11,R12 1k
LED2 RGB Co on Anode
R13,R15,R16 1k
LED3 RGB Co on Anode
R21,R22,R23 1k
LED4 RGB Co on Anode
R24,R25,R29 1k
LED5 RGB Co on Anode
R31,R32,R33 1k
LED6 RGB Co on Anode
R34,R35,R36 1k
LED7 RGB Co on Anode
P1 Connect COM to HV or VCC
This step installs and checks the LEDs (and neons if you chose that option). We install the “tick” of “colon”
indicators and all of the RGB back light LEDs. We do this now, because the RGB LEDs are ounted under
the tubes.
You ight want to test after you install each RGB LED. The startup pattern should slowly turn on and then
off the colons, the Red channel of the RGB LEDs, then the Green channel and then the Blue channel.
Warning!
The startup procedure only runs once, and then the clock goes into normal mode.
You should power off the clock before the Blue phase ends. If you don't do this, and the
startup test sequence co pletes, you can reset it by doing a “factory reset”. To do this,
connect the button and hold it down while powering on.

Trouble
shooting
I any o the channels does not go out completely:
So eti es the LEDs don't go out co pletely (especially the Blue channel, because the
blue LED is very sensitive). If this happens, carefully clean the flux residue fro around
Q3-6 (of course with the power off) using a cotton bud and pure alcohol. The FETs are very
sensitive to being partially turned on due to tracking over the flux. Let the board dry
co pletely before re-testing.
Notes:
•You can install either LEDs or neons as the colon indicators. There is a inor change to the
co ponents depending on which you choose.
•For LEDs: You need to connect P1 “VIN” to “COM” and choose 1k values for R38 and R39. You need
to take care of the polarity of the LEDs, following what is arked on the board.
•For neons: You need to connect “170V” to “COM” and choose 120k values for R38 and R39. The
polarity of the neons does not atter.
•Q3 - Q6 should be orientated with the flat side as shown on the board. So e FETs co e with the
leads in a row rather than in a triangle. If this is the case, bend the iddle lead slightly so that it fits
the holes in the board (see hint).
•R17 is needed to bias the LDR a bient light detection circuit, to ake sure that the LED lights up
reliably.
•Mount the RGB LEDs close to the board, but be
careful not to strain the LED too uch. Nor ally it
is best to ount the LEDs until the “lu p” in the
leads (about 3 – 4 proud of the board). If you
ount the LEDs too high, the tubes have to be
ounted uch too high fro the board.
•The “colon” LEDs need to be ounted proud of the
board, on oderately rigid extension wires. It is
not easy to esti ate the height they should be
ounted at yet (it will beco e clear once you
ount the tubes), so for the o ent, ake the
leads longer than you will need.
•Be careful to adequately insulate the LED leads
using so e heat shrink or excess plastic sleeving.
•The RGB LEDs have a tiny “o” on the board to indicate where the co on anode goes. The anode
is the longest lead of the RGB LED.

Hint: MPSA42/2N7000 ounting
To ount the MSPA 42 transistor or the
2N7000 FETs, bend the iddle lead back
slightly. It will then fit in the PCB without
proble s.