Nixie Clock Gemini Two User manual

Gemini Two Tube Clock 1
Update #1 (21st May 2019)
www.nixology.uk
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

Gemini Two Tube Clock 2
Update #1 (21st May 2019)
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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

Gemini Two Tube Clock 3
Update #1 (21st May 2019)
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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.

Gemini Two Tube Clock 4
Update #1 (21st May 2019)
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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.

Gemini Two Tube Clock 5
Update #1 (21st May 2019)
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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.

Gemini Two Tube Clock 6
Update #1 (21st May 2019)
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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

Gemini Two Tube Clock 7
Update #1 (21st May 2019)
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Gemini Two Tube Clock 8
Update #1 (21st May 2019)
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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
Update #1 (21st May 2019)
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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