My Nixie Addiction

PRISM – Direct Drive Clock

One thing that I’m not so clever with is the software that drives clocks. I can cope with updating displays, fetching time from NTP sources, changing LED colours and dimming Nixies.

I understand and use the ‘state machine’ concept to emulate a kind of multi tasking environment and I’ve even dabbled with interrupts but where It all falls over for me is in the publishing of web pages in order to change clock settings – that is knowledge that I just don’t have ?

I have built a few kits from and have seen their software develop as well as the range of clocks on offer. 

I was lucky enough to be offered a PCB for a prototype Direct Drive IN-18 based clock which had all the features I liked including web based configuration pages etc so I jumped at the chance. I procured the required components and pushed the whole thing together. Before long I had a clock with all the features I liked.

Both the hardware design and software are ‘Open Source’ so I decided to have a go at making my own version to work with Z566M (and pin compatible) tubes.

The circuit shares several common ‘building blocks’ with some of my designs including 5V (Buck Converter) and 170V (MC34063A) power supply circuits as well as twin HV5622 HV shift register / drivers.

Before long I had established the layout of a ‘controller’ board which had the power supplies, WeMos and level shifter components in place. I then set about the tube board which has the HV5622 Shift Registers, anode resistors and tube sockets. It also has provision for Colon Towers (LED or Neon) as well as neopixels for those who like the under tube lighting (like me).

PRISM Controller V1.1

PRISM Controller V1.5 with revised power supply layouts

PRISM Controller V1.568 with NCH6300HV module for the HV


Tube board for Z566M and pin compatible tubes

Tube board for IN-12

Tube board for GN-4P and pin compatible tubes

Tube board for Burroughs B5441 and pin compatible tubes

Tube board for QS27-1 and pin compatible tubes

Tube board for IN-18 tubes

Tube board for Z568 and pin compatible tubes including Dalibor Farny R|Z568M and Millclock ZIN70 with Nixilogy colon separators – 396mm x 60mm

Tube board for Millclock ZIN70 with suport for Millclock Colon Seperators –  440mm x 65mm

No sooner said – than done!
IN-4 Tube Board

Tube Boards

It rapidly dawned upon me that I could actually make tube boards for various other tube types by changing the footprints and adjusting the tube positions to suit. Accordingly I have already laid out tube boards for Z566M etc. ZM1020 top view tubes etc, IN-12, QS27-1 and IN-18.

All tubes being driven directly via the HV5622’s.  The HV5622 are designed to run at a 12V logic levels and although many designs work OK at 5V, given that the WeMos works at 3V3, the controller board features a CD40109 level shifter to take the 3V3 signals and turn them into 12V signals.

The two boards are connected uising headers and sockets on a 0.1″ pitch though rather than use the standard ‘Arduino’ style pins and sockets, I am using turned pins and turned pin sockets. The ‘socket’ pins are broken out out their plastic strips and recessed into 60 mil holes in the PCB. This reduces the inter-board gap to around 6mm which reduces the overall height of the clock. There are also  sets of holes that allow the tube boards to be fixed properly to the controller board using M3 hex standoffs. This makes it easy to fix the entire assembly into the chosen housing.

The controller board has develeoped a little and some minor modifications have been made to some of the tube boards but now – we have a clock (well, several in fact). 

Thus far I have tube boards for:  Z566,  General B13-B socket for top view tubes, IN-12, IN-18, QS27-1, NL5441 and R|Z568M – all ticking away – PM me if interested.

The controller for Z568/R|Z568M and ZIN70 tubes features the new NCH6300HV power supply from Omnixie.

I can supply bare boards with download links for the software, bill of materials,  with links to suppliers and construction notes or complete kits of components and PCB’s. PM me if interested.

If you have a tube type that is not catered for and you’d like a board for them, just let me know – I love a challenge (Nixies only, non biquinery). 

Single Board for R|Z568M, Z568 and ZIN70

The size of these tubes means that the PCB is going to be similarly large – I set myself the task of using the space around the tubes to accomodate the various power supplies and logic that the clock needs.

The result is a single board which accomodates 6 tubes with matching colon separators. All components are mounted on the underside of the board and protrude no more than 11mm from the board. 

The result is a low profile design that lends itself to a variety of housing concepts. I made a simple acylic case which is a snug fit to show how small it could be (well, small for a big clock!).

It has all the same features that the other PRISM designs do including WiFi Connect, Browser based config, NTP Sync,  RTC backup, Motion detect activation and configurable underlighting. This version features two NCH8200HV power supplies to ensure cool running. It also uses Dalibors ‘Proper Drive’ method where each cathode has its own series resistor so that all cathodes present the same overall brightness. That’s a lot of resistors, Surface Mount components have been used throughout.

Full kits and cases parts are available – ask me for details.

New IN-17, IN-12 and B-5991 versions

I have just created new and/or updated versions of the PRISM-18 design for these tubes. The IN-17 version is super small (to suit the tubes) and consits of three stacked boards (Controller, drivers and tubes) so that it looks nice and small from the front.

The IN-12 and B-5991 versions are very similar. I believe it is generally accepted that the B-5991 will plug in to an IN-12 socket though I have made a more closely spaced version for B-5991 as they are smaller and perhaps better suited to being closer together.

The IN-12 version has neopixel underlighting which sits within cutouts on the tube board so it does not interfere with the nipple at the base of the IN-12 whilst the B-5991 version has neopixels which sit on top of the tube board (The B-5991 does not have the same long descending nipple like the IN-12 does).

Acrylic case kits are also available for these kits.

IN-17 Tripple Board Sandwhich

IN-17 in Acrylic Case with 3D printed end parts

B-5991 version in acrylic case with 3D printed end parts

Construction Pictures

Here are a few shots of the boards under contstruction as well as a few glamor pics!

A closeup on part of th HV power supply.

More HV detail

WeMos Mini controls everything


Tube underlighting is not everyones cup of tea so there are configurable options which include turning them all off!

Burroughs B5092’s in action

The controller board behind a tube board

More HV Supply detail

The board interconnections are made by removing turned pins from turned pin socket strips which provides an economic and low profile interconnection