Nixie Clock Gemini Two User manual

Gemini Two Tube Clock 1
Update #1 (21st May 2019)
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Assembly Instructions
Gemini Two tube clock
nixology.uk
REVISION HISTORY
Issue
Number
Date
Reason for Issue
Draft 1
24/04/2019
New document
First Release
06/05/2019
Update #1
21/05/2019
Added initial setup and updating info

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Gemini Two Tube Clock –Features
•Hours, Minutes and Seconds display
•Date Display
•Temperature and Pressure display
•Drives a wide range of tubes
•Reliant on access to an NTP Time source for operation
•WiFi connection configured via a captive portal on the clocks own Access
Point
•Supports NeoPixels for tube illumination and confirmation of data type
being displayed
•Display is turned off from 21:00 to 06:00
•Support for OPTIONAL PIR device to trigger clock at any time
•PIR delay shorter during night time operation
•‘Slot Machine’ Cathode poisoning prevention routine

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Tubes Supported
The clock drives only two tubes, each one being driven directly by a dedicated
Nixie Tube Driver IC.
The connections for the tubes are provided by 2x6 pin headers with the following
details (viewed from the top of the connector):
Attach a suitable ribbon cable from this connector to your choice of tubes*. The
arrangement of the signals on the connector matches those available from PV
Electronics for the QTC clock range. Tube Cells for other tube types are available
from nixology.uk including those for the connection of Z566M/GN4P, IN-18, ZIN-
18 and RJ568M (Dalibor Farny).
Tube cells for the larger tube types incorporate connections for additional
APA106 LED’s
*Depending on the chosen tube type it may be necessary to change R3 and R4
from the 10k supplied to match your tubes.

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SAFETY
DANGER: This clock includes an NCH8200HV 170V power supply module. This
generates nominally 170 Volts DC. Assembly may only be undertaken by
individuals who are suitably qualified and experienced in electronics assembly
and are familiar with safe procedures for working with high voltages. If in doubt,
refer to a suitably qualified engineer before proceeding.
The voltages generated by this circuit can give a potentially LETHAL
ELECTRIC SHOCK.
DISCLAIMER: This product is supplied as a kit of parts, intended only for
suitably qualified electronic engineers, who are suitably qualified and
experienced in electronics assembly, and are familiar with safe procedures for
working with high voltages. The supplier, their agents or associates accept no
liability for any damage, injury or death arising from the use of this kit of parts.
This is not a finished product, and the person assembling the kit is responsible
for ensuring that the finished product complies with any applicable local
regulations governing electrical equipment.

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TOOLS AND EQUIPMENT REQUIRED
Tools required to assemble the PCB.
The following tools will be required to assemble the PCB:
Soldering iron with a small tip (1-2 mm).
Wire cutters to trim the excess component leads after soldering
Wire strippers
Multimeter for voltage tests and for identifying the resistors.
Laptop or mobile device with WiFi for initial setup.
Materials you will need.
Solder –lead / tin solder is highly recommended. USE LEAD/ TIN SOLDER!
Lead free solder, as now required to be used in commercial products in Europe,
has a much higher melting point and can be very hard to work with. Desoldering
wick (braid) or a ‘solder sucker’ can be useful if you accidentally create solder
bridges between adjacent solder joints.
Other items you will need.
The clock kit does not include a power adapter. The clock is designed to be built
in to your own housing design and as such you will need to make your own
power supply arrangements. You will need to provide a 12V DC regulated supply
capable of supplying a minimum of 500mA. Take care to connect the power the
right way around.
This clock is supplied as a kit of parts, please pay careful attention to the order
with which components are added and voltage measurements are taken.
DO NOT –solder the Buck converter to the clock PCB without having first
soldered R1 –R4 and the 8 pin DIL socket on the top side.
DO NOT insert the WeMos, HV Power supply or other IC’s before you have
successfully measured 5V from the 5V test point.

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Component List
QTY
Description
3
16 pin DIL IC Sockets
1
8 pin DIL IC Socket
1
4 Way Header Socket for Neopixel connection
1
6 Way Header Socket for BMP280 connection
1
NCH8200HV 170 V PSU –includes 4 x mounting pins
1
12V to 5V Buck Converter PSU module
4
1mm Socket Pins
2
2 x 6 Male Headers
4
Mounting pins for 12v to 5v converter (strip of 4 single header
pins)
1
74595 Shift Register IC
2
74141 or K1551 Nixie Driver IC
2
EL817 Opto Coupler IC
2
R1, R2
100R Resistor
2
R3, R4
10K Resistor
0
100nf Capacitors –optional -
4
M3 Hex Standoffs
4
M3 Screws
1
BMP 280 Temperature / Pressure Sensor
1
5V LED WS2811 / APA106 or similar
1
WeMos D1 Mini with 2 x pin headers and 2 x socket headers
Pre-Programmed
1
Two Tube Clock PCB
You will also need 2 x your choice of Nixie Tubes (not supplied). The board uses
the same 2x6 header arrangement as the PV Electronics QTC clock so any PV
Electronics QTC compatible tube cell PCB will work, just connect via a ribbon
cable with suitable connectors.
Anode Series Resistor Selection
R3 and R4 have been supplied as 10K which should provide an anode current in
the region of 3mA from the 170V supply when using a tube with a maintaining
voltage of around 140V.
You may wish to vary this value up or down depending on your selection of Nixie
Tubes. You will need to know the Anode Voltage required for your tube and the
desired current. The HV supply voltage is 170V.
Consider a ZM1210 from Telefunken, it has a maintaining voltage of 140V and
requires 2mA.
From Ohms Law (i=v/r or r=v/i), r=(170-140)/0.002 = 15K
Similarly, for a ZM1175 from Mullard, it has a maintaining voltage of 145V and
requires 2.5mA so r=(170-145)/0.0025 = 10K

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Gemini Two Tube Clock 8
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Assembly of the PCB
DUE TO PRODUCT DEVELOPMENT AND IMPROVEMENTS, YOUR PCB MAY
NOT LOOK EXACTLY LIKE THE ONE PICTURED.
Resistors
Start by adding the resistors to the top side of the board. If you are in any doubt
as to what the values of the resistors are then use a multimeter to check them.
R1, R2 100R (Brown, Black, Black, Black)
R3, R4 10K (Brown, Black, Black, Red)
Sockets and Headers
These are all mounted on the top of the PCB. Add the 3 x 16 pin IC Sockets –
note that the orientation differs between each socket, take care to orient the
‘notch’ in the socket with the symbol on the PCB.
Next Add the two 2x6 male headers for the tube connections.
Next Add the 8 pin DIL socket for the Opto Couplers.

Gemini Two Tube Clock 9
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170V Power Supply
NCH8200HV Mounting position
This can be mounted either on the top of the board or the bottom. Take
care to solder the pins to the right side of the NCH8200HV and the
socket pins to the right side of the clock board to suit your preferred
mounting position.
Please note that if the NCH8200HV is mounted on the underside of the
PCB then it will not be possible to connect a USB cable to the WeMos for
monitoring status information without inserting the optional ‘extension
headers’ that are supplied with the WeMos.
If mounting the NCH8200HV under the board then mount the pins on the
component side of the NCH8200HV.
If mounting the NCH8200HV on the top of the main board then mount the pins
on the underside of the NCH8200HV.
Add the 4 x socket pins for the NCH8200HV power supply, do this by first
soldering the 4 pins that came with the power supply to the power supply itself.
Next push 4 x socket pins onto the power supply pins and inset the completed
assembly into the PCB and solder the socket pins to the main board.

Gemini Two Tube Clock 10
Update #1 (21st May 2019)
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Remove the power supply and trim the short ends of the socket pins on the
other side of the board.
Mounting pins cut off after soldering (NCH8200HV mounted on bottom of board)
NCH8200HV when mounted on the top of the board

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NCH8200HV mounted on the bottom of the board
Remove the NCH8200HV from the clock

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Headers for BMP280 and Neopixels
Solder the 4 way header for the NeoPixel connections and the 6 way header for
the BMP280 sensor. Both are mounted on the top of the board.
Only three out of the four connections are used for the Neopixels and only four
out of the six connections are used for the BMP280.
BMP280
For testing this can be plugged directly in to the header on the clock PCB though
for better results it could be mounted remotely where it may not be affected so
much by any heat generated by the clock and associated components.
Solder the header pins to the BMP280. Which side you solder the pins to will
depend on your chosen mounting method. This example shows them set for
direct attachment of the BMP280 to the PCB Header. Be sure to align VCC on the
BMP280 with VCC on the PCB.
Turn the board over and solder the following components:
WeMos mounting pins and sockets
Insert the two rows of header pins (that were supplied with the WeMos) into the
PCB ‘long’ end first, leaving the ‘short’ ends for soldering to the WeMos (for
location only DO NOT SOLDER). Put the Wemos on to the two rows of pins
and solder the pins to the Wemos ONLY.

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Take care to orient the WeMos correctly so that the pins get soldered to the
correct side!

Gemini Two Tube Clock 14
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Now remove the Wemos and insert the two sockets headers (that were supplied
with the WeMos) into the underside of the PCB and then plug the WeMos in to
these headers. The purpose of plugging the WeMos in at this stage is to help get
the socket headers straight.
Turn the board over and solder the sockets in to place.
Your board should now look like this:

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Remove the WeMos from the clock PCB
12V Buck Converter pins and sockets –this is designed to mount ONLY
on the underside of the PCB
PLEASE NOTE –PIN/SOCKET Method now superseded –skip to the
‘Alternative Space Saving’ method
Follow the same procedure as used for the NCH8200HV power supply.
Start by soldering 4 x pins to the underside of the Buck converter (Not the
component side).

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Push 4 x socket pins on to the pins that you just soldered and push the complete
assembly in to the PCB from the Underside.
Solder the pins and remove the Buck Converter. When re-fitting, make sure that
you have the buck converter the correct way around, 12V ‘IN’ towards the outer
edge of the PCB.
Alternative SPACE SAVING method:
This MUST BE DONE AFTER soldering R1, R2, R3, R4 and the 8 pin DIL
socket in to place
If you would like to reduce the overall height of the clock then use the four
single pins (supplied as a 1x4 way header pins that you can cut in to 4 individual
pins) by soldering the ‘short’ ends to the Buck Converter.
Mount the Buck Converter on the underside of the PCB taking care to mount it
the right way around the solder in to place from the top side of the PCB.

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Update #1 (21st May 2019)
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This MUST BE DONE AFTER soldering R1, R2, R3, R4 and the 8 pin DIL
socket in to place. Be sure to clip the legs of these components as close to the
PCB as possible so that there is sufficient clearance between them and the Buck
Converter PCB. With the mounting pins provided (4 way header pins) there is no
need to trim the legs of the 8 pin DIL socket used for the opto couplers as there
will already be sufficient space Trim the legs of R1, R2, R3 and R3 so they are no
longer than the IC socket pins.
REMEMBER, THIS MUST BE DONE AFTER soldering R1, R2, R3, R4 and
the 8 pin DIL socket in to place and trimming their leads.

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First Test –Setting the 5V supply.
With ONLY the Buck converter mounted on the board, connect a 12V supply to
the PCB at the points provided taking care to connect the supply the right way
around and measure the output of the Buck converter with a multimeter by
using the GND and 5V test points. Adjust the potentiometer with a small
screwdriver until 5v is measured. IT IS IMPORTANT THAT NO OTHER
COMPONENTS ARE PLUGGED IN TO THE BOARD AT THIS STAGE AS THE
BUCK CONVERTER WILL ALMOST CERTAINLY BE SET TO OUTPUT MORE
THAN 5V WHICH COULD DAMAGE OTHER COMPONENTS.
<Picture of 5V Test>
Do not proceed until you have a solid 5V reading.
Disconnect the 12V supply.
Second Test –checking the 170V supply
Inset the NCH8200HV power supply into the sockets on the board. Re attach the
12V supply and check that 170V is being produced by the NCH8200HV by
connecting a multimeter to the GND and HV test points.
<Picture of 170V Test>
Do not proceed until you have a solid reading in the region of 170V to
174V.
REMOVE THE POWER CONNECTION
Continue as follows:
Plug in the following on the top side of the PCB
2 x 74141 or K1551D1 drivers and 1 x 74595 shift register into their respective
locations according to the markings on the PCB taking care to align the notch on
each IC with the notch on the socket and PCB.
2 x EL817 Opto Couplers taking care to align them correctly. Pin 1 has a small
‘dot’ and should be located towards the edge of the PCB.
1 x BMP280 sensor module –this can be mounted directly or via a length of
cable if remote mounting is preferred. If it is not properly connected then the
temperature and pressure will not be displayed.

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Plug in the following on the bottom of the PCB
1 x WeMos D1 Mini, taking care to align the pins correctly and orient the WeMos
so that the ‘Antenna’ end is closest to the outside edge of the PCB.

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Connect 1 or more LED’s to the header on the PCB. These LED’s require 5V, GND
and Data In to operate. Connect the ‘data in’ of subsequent LED’s to the ‘data
out’ of the previous one.
The APA106 LED has two longer legs, two shorter legs and a flat side and has
the following connections:
For testing purposes, attach the supplied APA106 LED using only DIN, 5V and
GND as follows:
<Picture of APA106 in position>
Reattach the 12V supply and switch on, at this point, the WeMos will be trying to
connect to a WiFi signal and failing.
You could also connect the WeMos to a PC using a micro USB cable (not
supplied) and use the terminal mode of the Arduino IDE or PuTTY to monitor the
output of the serial port on the Wemos at 9600 baud for status information.
Note that this will not be possible if you have mounted the NCH8200HV
on the underside of the board unless you insert the additional pair of
long legged header sockets between the WeMos and the Clock PCB for
testing purposes only.
Configuration of WiFi Connection
The software is using a standard Library for managing the WiFi connection.
When it fails to connect, it will set itself up as an Access Point with a Captive
Portal.