Arduino nixie v41 User manual

Arduino Nixie Clock v41
Operating Instructions
&
Construction Manual
Document V0041a

Contact Information
If you want to get in contact with us, please email to:
[email protected]
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. Contact us for
information. Usually this works out as about 10%.
Software
The software is available on GitHub at the address:
https://github.com/isparkes/ArdunixNix6/releases
This board works with Release “Revision 4 boards” under the “Releases” tab.
roubleshooting
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 manual, there is a troubleshooting section, which goes through some of the common
problems.

Description
The Arduino Nixie Clock is a beautiful mix of old and new, resulting in a high accuracy, low power clock
which will be a talking point in your home.
The clock has the following features:
•Battery backed, temperature compensated, high accuracy clock. The accuracy is Accuracy ±2ppm
from 0°C to +40°C. (Maximum 1 minute per year).
•The battery life should be 3 years in normal use.
•Retains the date and time even when turned off (not just for a few minutes, but for as long as the
battery lasts)
•Leap Year Compensation Valid Up to the year 2100
•Based on the Arduino micro-controller: Easy to program an well documented.
•Open source hardware and software. Nothing is hidden in this clock.
•You may modify and load the software
•Low power consumption.
•Anti Cathode Poisoning (ACP) makes sure that the tubes will stay healthy for many years with no
intervention from you.
•All settings are stored in non-volatile memory. Once they are set, they are remembered forever, or
until you change them again.
•RGB back lighting allows you to set the the color of the back lighting to practically any color you
desire.
•Ambient light sensing, with automatic tube dimming, which sets the tube and LED brightness
according to the light conditions. The tubes could be disturbing during the night if they are left at
full brightness.
•Absolutely silent operation. Some Nixie clocks emit an irritating “buzz” or “hiss” which is especially
annoying if you keep the clock in a bedroom.
•Long tube life: The multiplexed display and automatic dimming used in this design extends the life
of the tubes indefinitely. Some other designs run the tubes too “hard”, and this causes a rapid
degradation in the useful life of the tube.
•Automatic week day or weekend blanking, extends the life of tubes even further
•Automatic time 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 dimmed. In the middle
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 dimmed
•The micro-controller can be reprogrammed using the ICSP interface provided on the board

General
The clock has different modes of operation, which you select using the pushbutton. When you start the
clock up th very first time, it will start in “Time Display Mode”. We set it up to be the right time for where
the clock is being shipped to, so in the best case you will not even need to set the clock the first time!
The other modes of operation are described in the following sections.
Safety
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 means, please do not use this clock and return it for a
full refund.
A shock from 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.
REPEA : 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 match the power adapter you have attached. During this time you might hear
some faint crackling noises from the generator. This is normal.
After finishing the calibration, the version number (“00:35:07”) will be displayed for about a second. The
clock will then go into normal operating mode.

ime Display Mode
Normally, the clock will show the time. To show additional information press the button with a “short”
press. Each press cycles through the following information. After 5 seconds, the display will revert to the
normal time display.
Mode Description Values
Date Date. The current date will be shown.
Temp emperature. The current internal temperature inside the clock
case will be shown in degrees Celsius. If this goes above 40, you
should consider ventilating the case, because the temperature
compensation is not able to work at such high voltages, and the
clock life may be reduced, and the time may drift.
Light Ambient Light Reading. This shows the current ambient light
reading from the LDR (light dependent resistor). It is a normalized
value, and goes between 100 (dark) to 999 (bright). This controls the
dimming of the tubes.
100: darkest
999: brightest
Version Display the version number. The format will be :”VV vv 07”, where
major version is “VV”, minor version is “vv” and the “21” is the id for
the version display.
00:35:07
Setting Mode
To enter setting mode, press the button for more than 1 second (“medium press”). The “RGB back light”
LEDs will start to flash white. The number of consecutive flashes indicates the mode you are in.
Each medium press of more than 1 second will move the setting mode onto the next. When you finish the
setting modes, the clock returns to normal time display mode.
o exit the setting mode before going through all the options, press the button for more than 2 seconds
(“long press”). The “RGB back light” LEDs will return back to their normal operation. Another way of exiting
is to cycle through all of the setting options, after which you will return to time mode.
To change a setting, press the button for less than one second, and then release it (“short press”).

Mode Description Values
ime mode. This is the normal mode and displays the time. It is the
normal start up mode of the clock. If you do nothing. The clock is in
this mode.
In this mode a short press cycles through the values given in “Time
Display Mode”, but always returns to the standard time display after
5 seconds.
ime and Date Settings
Set minutes. Each short press will advance the minute. The
minutes roll over back to 0 ffter reaching 59 minutes. Each time you
set the minute, 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 mode).
Set Day. Each short press will advance the day. The day roll over
back to one after reaching the maximum number of days in the
month.
Set Month. Each short press will advance the month. The month
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
mode.
“1” = 12 hour
“0” = 24 hour
default: 0
“01”
flashing
Blank leading “0”. Blank out the leading “0” from 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 from “9” to “0”.
“1” = enable
“0” = disable
default: 1
“03”
flashing
Date format. Set the format 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 mode
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 mode
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 some
people might find this disturbing. Using this setting, you can stop
ACP happening when the display is fully dimmed (e.g. at night).
“1” = don t do ACP
when dimmed
“0” = do ACP always
default: 0
Special Effects Settings
“08”
flashing
Fade Speed Slower. Each short press will make the fade speed
between digits slower.
Default: 50
Max: 200
Min: 20
“09”
flashing
Fade Speed Faster. Each short press will make the fade speed
between digits faster.
Default: 50
Max: 200
Min: 20
“10”
flashing
Scroll-back Speed Slower. Each short press will make the “scroll-
back” speed slower.
Default: 4
Max: 40
Min: 1
“11”
flashing
Scroll-back Speed Faster. Each short press will make the “scroll-
back” speed faster.
Default: 4
Max: 40
Min: 1
Back Light Settings
“12”
flashing
Back Light Mode. This sets the mode of the back light.
“Fixed” mode will show the back light color according to the Red,
Green and Blue channel intensities.
“Pulse” will make 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 randomly, and does not use the Red,
Green and Blue channel intensities. These settings will be skipped if
cycle mode is selected.
Options “0”, “1” and “2”, do not dim with the bulbs. Options “3”, “4”
and “5” do.
“0” = Fixed
“1” = Pulse
“2” = Cycle
“3” = Fixed/Dim
“4” = Pulse/Dim
“5” = Cycle/Dim
default: 0
“13”
flashing
Red Channel Intensity. Sets the maximum intensity of the red
channel back light. This will be dimmed according to the display
dimming. If you are in cycle mode, this setting will be skipped.
Default: 15
Max: 15
Min: 0
“14”
flashing
Green Channel Intensity. Sets the maximum intensity of the green
channel back light. This will be dimmed according to the display
dimming. If you are in cycle mode, this setting will be skipped.
Default: 15
Max: 15
Min: 0
“15”
flashing
Blue Channel Intensity. Sets the maximum intensity of the blue
channel back light. This will be dimmed according to the display
dimming. If you are in cycle mode, this setting will be skipped.
Default: 15
Max: 15
Min: 0
“16”
flashing
Cycle Speed. If you are in cycle mode, this controls the speed at
which the colors cycle. The higher the number, the slower the
colors will change.
Default: 10
Max: 64
Min: 4
HV Generation Settings (See “HV Settings” note)
“17”
flashing
HV arget Voltage Higher. Each press sets the HV target voltage
higher by 5V.
Default: 180
Max: 200
Min: 150

“18”
flashing
HV arget Voltage Lower. Each press sets the HV target voltage
lower by 5V.
Default: 180
Max: 200
Min: 150
“19”
flashing
PWM On ime Longer. This setting controls how long the PWM On
pulse is. Normally 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 ime Shorter. This setting controls how long the PWM On
pulse is. Normally 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
Information Settings
“21”
flashing
Current case temperature. Show the current temperature inside
the case (used as part of the temperature compensation for the
clock crystal).
“22”
flashing
Clock version. Show the clock software version.
Digit est. 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 IRF740 MOSFET nor the 7805 voltage regulator is running too hot. If either of these
components gets too hot, either adjust the high voltage settings or add a heat sink.

Display Blanking Mode
During display blanking mode 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 example I have a setting saying that the clock is
blanked on weekdays between 7am and 4 pm, while I am out at work. At weekends, the display runs all the
time.
You are also able to override the blanking. Press the button while the clock is blanked, and the display will
come on again. Pressing the button will display the time for about a minute (60 seconds, but the display is
only blanked on the minute change).
If you press the button multiple times within 5 seconds, the blanking will stay off for longer periods:
•1 Press: 60 seconds
•2 Presses: 1 hour
•3 Presses: 4 hours
ube Healing Mode
After a long period of time, tube filaments which are not often used (e.g. the “9” on the tens of hours or
minutes) can get dim, despite the ACP that is regularly done.
If you make a “super-long” press of the button (more than 8 seconds), the clock will enter filament healing
mode. All the power will be placed through a single filament of a single digit to clean it. A short press will
change the selected filament.
Another super-long press or cycling through all the filaments will return the clock to normal.
Caution! Don t leave a single filament in this state for an extended period of time. It is a harsh process,
and may damage the tube if you leave it in this mode for too long. Normally a few minutes will restore the
cathode digit.
Factory Reset
To reset the clock back to initial settings, hold down the button while powering on. The “tick” LED will flash
10 times 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 more than 12V be aware that you might have to provide a heat sink for the power components
and adjust the HV voltage generation. It is not advised to use more than 12V.
The absolute maximum permissible is 24V DC. Higher voltages than this will surely damage the clock.

Board layout
For reference, the board layout is as shown (viewed from 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, from 7.5V – 12V. Higher voltages
may be possible, but could cause the digits to flicker if the voltage is
too high, and you might have to provide a heat sink for the the
MOSFET and voltage regulator.
The absolute maximum input voltage is 24V. Any higher voltage
than this will damage the board within a few seconds!
The input VIN is protected against the input being connected
reversed.
The input current ranges from 300mA to 1A depending on the size
of the tubes and the number of LEDs you are driving.
GND: The negative side of the input supply
VIN: The positive side of the input supply
VCC: Output of regulated 5V
HV OU : Output of high voltage for driving external neons etc.

FRONT These are the controls that go on the front panel: The input button
and the Light Dependent Resistor to detect ambient 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.
B N1: The other lead of the button is connected to this input
DLS: “Dimming 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.
LED The LEDs are connected to these sink (they consume current, not
source it) terminals. To connect up you take the positive sides of the
LEDs to either VIN or VCC and connect the negative sides of the
LEDs to these terminals.
R: PWM cathode connection for the back light RED channel.
G: PWM cathode connection for the back light GREEN channel.
B: PWM cathode connection for the back light BLUE channel.
: PWM Cathode connection for the blinking “tick” LED.
RTC The connection for the RTC (Real Time Clock) module. Connect this
to the appropriately marked terminals on the RTC module.
CATHODES The terminals to the cathodes (individual digits “0” - “9”) for each
tube. Terminal “0” drives the cathode “0” and so on.
ANODES The terminals to the anodes for each tube. The allocation of anode
to tube is:
1. Tens of hours
2. Hours
3. Tens of Minutes
4. Minutes
5. Tens of seconds
6. Seconds

Schematic
Below is the schematic for the clock.

And for the external components, showing how they are connected.
One side of the LDR and switch are connected to ground (pin 1, SV2).
The LEDs are driven from VCC or VIN, depending on the configuration. Here are some suggestions:
1 ICK LED:
Run the TICK LED directly from the board, either from VCC or VIN.
2 ICK LEDs:
Run the two TICK LEDs in series from VIN. You don t need a balancing resistor because the LEDs are in
series.
4 ICK LEDs:
Run the TICK LEDs by putting 2 in series, and running the two series combinations in parallel. In this case
you need a 1k balancing resistor in each series.
1 RGB Back Light LED:
Run the RGB LED directly from the board, either from VCC or VIN.
Multiple RGB Back Light LEDs:
Each RGB LED needs a series balancing resistor on each Red, Green and Blue cathode. I normally run 6 in
this configuration.

Construction
Preparation:
You should have a small tipped soldering iron, some thin (< 1mm) solder, and electronic side cutters.
Kit Contents:
When you unpack the kit, you should find the following contents as listed in the BOM (Bill of Materials). It is
best to check the contents before you start, and notify me straight away if you are missing any
components.
Please see the appendix to help you identify individual components.
Low Voltage Circuit:
Parts List:
D1 IN4001
C2 100nF
C4 220uF
IC1 7805TV
C9 220uF
R8 2.7k
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 from the power adapter down to a known and stable 5V to drive the micro-controller
and the 74141/K155ID.
Put the parts on the board in the marked locations in the order they appear on the list.
Notes:
•See the section on “Component Identification” for help with identifying the components.
•D1 and D2 look very similar, but have different jobs to do. Be careful to get the 1N4001 and not the
UF4004.
•D1 should be placed so that the white stripe on the body lines up with the white stripe on the
board.
•C9 must go the right way round. The negative side is marked with a stripe. (See hint)
•The LED must go with the right polarity. The side which has the shorter lead goes nearest the
diode. (See hint)
•Put IC1 so that the metal tab lines up with the white stripe on the board. The metal side faces to
the outside of the board.

Test Step
Once all the components are on the board, hook up the power, and check that the power
LED comes 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 come on, turn off immediately to avoid damage to the components.
Check your soldering and the polarity of the components.
If the components are in the right way, connect the power again, and check that the 7805
voltage regulator does not get hot. If it does not, measure 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 measure 0.7V less than the input voltage.
If all is well, proceed to the next step. If not, check carefully the orientation of the components and the
power leads. Diode D1 protects the board from having the power connected inverted.
If the LED comes on, check for a few seconds that the 7805 does not heat up. It should stay almost 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 something like this:
220uF capacitor “stripe”
The LED

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

High Voltage Circuit:
Parts List:
C5 22pF
C6 22pF
C1 2.2uF 450V
C7 100nF
C8 100nF
D2 UF4004
S28 SOCKET 28
Q2 16MHz
L1 100uH
R7 2.7k
Q1 IRF740
R9 390k
R10 4.7k
R18 10k
IC2 MEGA8-P
The high voltage circuit uses the micro-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 dimming.
Notes:
•See the section on “Component Identification” for help with identifying the components.
•C4 must go the right way round. The negative side is marked with a stripe (see hint).
•Put Q1 so that the metal portion lines up with the white stripe on the board. The metal 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 micro-controller socket in first. Make sure that the depression on the end of the socket
lines up with the marking on the board. When you put the chip in, the chip should go in with the
depression faces to the outside of the board.
Once all the components are on the board, hook up the power. Give your work a careful check to make
sure that the orientation of the components is right. Especially check that the stripe on C1 is facing the top
of the board (not near the 170V test point).
Test Step
Apply power to the board again. Listen for any stressed sounding buzzing or humming,
and check that neither the 7805 nor the IRF740 get excessively hot.
Check that the power LED still lights.

Trouble
shooting
If you hear any angry sounding buzzing turn the power off immediately and check
the orientation of C1! The circuit should run almost silently, with only a very faint
“crackling” sound.
If you can t reach the target voltage, turn off and check the polarity of your components,
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
waveform to the HV generator, which is being turned off and on by the voltage detection,
trying to achieve the target voltage (180V default).
Be careful, we are dealing with high voltages now! The voltage may be significantly higher than 170V at
the moment, 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 might have a slight
“sawtooth” appearance if you view it with an oscilloscope.
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 mistake. If you are sure you won t be needing it, you can snap the extra pin off and populate only the
bottom 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 lamp if you have one. Temporarily connect the neon
lamp 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 lamp should come on.
Trouble
shooting
Q1 can get warm, but should not get too hot to touch. If it gets hot, you need to check
the orientation of the components and that there are no solder bridges.
If 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.
•Temporarily connect the LDR and re-test.
•Temporarily 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 small piece of tape, and the solder
one leg in place. You can hold the socket
firm while you “wet” the solder again,
which will hold the socket firmly enough
to solder the remaining pins. One leg is
usually enough to hold the socket in place
while you solder the others.
Mounting 28 pin socket

At the end of the high voltage circuit build, your board should look like this:
High Voltage Circuit

“ ICK LED” Circuit:
Parts List:
RTC RTC (see note)
SV4 CONN_RTC (see note)
R19 1k
R23 1k
Q6 2N7000
TICK LED LED 5mm
SV6 CONN_LED
SV2 CONN_FRONT
R11 10k
This step will check that the Micro-controller can talk to the RTC module, and that the time counting is
working properly. The flashing rhythm of the “tick” LED comes from the RTC module, and we want to check
that we are able to communicate with the RTC module..
Notes:
•If you want to have two LEDs for the “tick” circuit, you can place these in series, and power them
from the unregulated VIN voltage.
•Q6 should be orientated with the flat side as shown on the board. Some FETs come with the leads
in a row rather than in a triangle. If this is the case, bend the middle lead slightly so that it fits the
holes in the board (see hint).
•The RTC module has two sets of contacts on it. You can use either the side with the pins on it or
wire up the other side with flying wires. If you use the side with pins, you should carefully remove
the two unused pins (see hint). If you use the contacts on the module, you should leave CONN_RTC
off the board.
•If you receive the connector header as a single strip, break off 4 pins for SV6 and 4 pins for SV2.
•The LED must go with the right polarity. The “-” side has a flat on it, and has the shorter lead (see
hint), and must be connected to pin 4 of SV6.
•R11 is needed to bias the LDR ambient light detection circuit, to make sure that the LED lights up
reliably.
The LED should be wired up with the longer lead to pin 4 of the CONN_FRONT (SV2) connector and the
shorter lead to pin 4 of the CONN_LED (SV6) connector. (Pin 1 has a little “o” beside it on each connector on
the board).
Test Step
Once you have populated the components, power on. The LED on the RTC module should
come on, and the “TICK” LED should flash on and off slowly (on for one second, off for
one second). It might take a second or two to come on, but after that should “pulse” on
and off.