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So there are plenty of display modules available to work with an SPI bus, mostly based around LED or LCD technology. But I wanted to re-use some old Nixie teck. This Instructable is what I came up with.

The completed module is compact and fairly robust so I don’t need to worry about it getting knocked around on my workbench, and its a simple task to re-use the display module with multiple projects.


4 circuit boards simplifies construction and testing.
PIC16F15344 Micro-Controller - 32MHz with internal SPI bus.
Operating voltage range from 2.3 to 5.5 volts.
No need for level shift circuitry on the SPI bus - just run the micro-controller at the same voltage as the bus.
Internal buck converter (6 to 12 volt input) - creates the 170 volt required by the Nixie tubes.
All high voltage connections are kept internal, minimising the risk of accidental contact.
Notes on construction:

I think of Perfboard as a sheet with holes drilled on a 0.1″ grid. The holes are plated on both sides, and each hole is an individual electrical node. I’ve never been a great fan of the stuff because I think the end results look messy, and I tend to use strip board or Veroboard instead.

But it occurred to me, Perfboard could be a lot neater if connections were made using insulated wiring on the component side of the board. And if that connecting wire was 30AWG wire-wrap cable, I could maximise the wiring density. And by using multiple wires to each hole, I wouldn’t need so many connections, which would maximise the component density.

So that’s the approach I’ve used on this project. The layout takes a bit more planning than usual, and assembly is a layered approach with wire connections going on first, followed by the components, then soldering. But the end result is compact and quite neat.

30 AWG wire-wrap cable is used throughout - anything larger just won’t fit.
Perfboard MUST have through hole plating to ensure solder can flow into the hole rather than just sitting as a dirty great blob on one surface of the board.
Component layout is more of a tag-board approach, with component leads and connecting wires sharing holes in the circuit board. This approach allows for a high component density.
Wires aren’t soldered until all components and wires are in place. The circuit boards have up to 4 wires per hole.
All wires are trimmed as close to the circuit board as possible before soldering.
When soldering, the through hole plate draws solder into the holes, minimising the height of the solder joints and reducing the risk of shorts between adjacent circuit boards.

- 2 x Double Sided Prototyping Circuit Board FR4 - 6 x 8 cm - cut down into 4 smaller boards measuring 8 x 20 holes (First photo)
- 40 Pin 2.54mm Male PCB Single Row Right Angle Header Strip Connector Arduino (Second photo)
- 5 x male to female Dupont connecting cables.
- Garden peg - 3cm width - insulated (fourth photo)

Nixie Board:

- Circuit Board, 8 x 20 holes, 4 corner holes drilled for M3 spacers, 3 center holes drilled for Nixie tubes.
- 4 x 10mm, M3, male to female stand-offs
- 30 AWG (wire wrap) connecting cable
- 3 x IN-17 Nixie tubes

170V PSU Board:

- Circuit Board, 8 x 20 holes, 4 corner holes drilled for M3 stand-offs.
- 4 x 10mm, M3, male to female stand-offs
- 2 pin, right angle Dupont connector - cut from larger strip
- 3 x vero pins
- 30 AWG (wire wrap) connecting cable
- 9 volt battery connector, with (female) Dupont connectors.
- C1: 220uF @ 16volt electrolytic capacitor, 6mm diameter
- C2: 2.2nF minature ceramic capacitor
- C3: 100pF minature ceramic capacitor
- C4: 2.2uF @ 250volt electrolytic capacitor, 6mm diameter
- R1: 1K 0.25W resistor
- R2: 10K 0.25W resistor
- R3: 2.2K 0.25W resistor
- R4: 220K 0.25W resistor
- R5: 1K pre-set potentiometer - Bourns RLB0712-101KL
- T1: BC547 NPN transistor
- T2: IRF740 N-Channel MOSFET
- IC1: 555 timer
- D1: UF4004 ultrafast Recovery Rectifier
- L1: Bourns RLB0712-101KL Inductor, RLB Series, 100 µH, 320 mA, 0.4 ohm, ± 10%

HV Driver Board:

- Circuit Board, 8 x 20 holes, 4 corner holes drilled for M3 stand-offs.
- 4 x 10mm, M3, male to female stand-offs
- 30 AWG (wire wrap) connecting cable
- 13 x MPSA42 High voltage, NPN transistor
- 3 x MPSA92 High voltage PNP transistor
- 6 x 100K 0.25W resistor
- 13 x 33K 0.25W resistor

Micro-controller Board:

- Circuit Board, 8 x 2 0 holes, 4 corner holes drilled for M3 stand-offs.
- 4 x 8mm, M3, male to female stand-offs
- 4 x M3 4mm machine screws
- 2 x 5 pin, right angle Dupont connector - cut from larger strip
- C1: 0.1uF ceramic capacitor
- C2: 220uF @16V electrolytic capacitor, 6mm diameter
- R1: 10K 0.25W resistor
- IC1: PIC 16F15344 micro controller

Equipment: (Third photo)

- Multi-meter: with 200 volt range and a continuity tester.
- Hand held miniature drill: Required to drill out the corners on the circuit boards.
- Pickit 3 + MPLAB XIDE: Debugger/programmer or some other means to compile a C program and deploy it to the PIC mcrocontroler.
NOTE:The MPLAB - XIDE application can be a steep learning curve. This project assumes you are familiar with the application, and can create and configure a new project to compile and deploy the code for the micro-controller.”

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