Słomkowski's technical musings

Playing with software, hardware and touching the sky with paraglider.

Octoglow VFD - Fallout-inspired display

This eponymous project mixes modern technologies with obsolete ones like vacuum tubes and germanium transistors. Basically, it is an informational display heavily inspired by Fallout games, which you can put on your desktop.

I like post-apocalyptic themes. And Fallout games. There might be a special kind of pleasure when reading some post-apo SF novel and looking at your custom-made PipBoy derivative. Therefore I decided to build one! For you who don’t know how PipBoy 2000 from Fallout 1&2 looks like:

PipBoy 2000

Since building real functioning PipBoy with genuine vintage components would be a monumental task, I focused on stationary device. In fact, I was particularly inspired by this contraption:

Vault-Tec simulator

In-game, it is supposed to be a post-apocalyptic survival simulator proudly made for you by Vault-Tec. It has an open layout: the chassis is a steel skeleton which holds all internal components in place, they are clearly visible by the way. Gluing the ideas together, I came up with following requirements:

Early concept consisted of only one PCB - the one containing the dot-matrix display. After completing this module I decided to create more and mount them on unusually wielded steel chassis made of two octagons - therefore Octoglow was chosen as the name of the device. The project since then has grown seriously but so has the fun!

Currently, the device is made of following modules:

There is still quite a lot of space within the chassis, I may add another board in the future. If you have any ideas for it, let me know!

Every PCB was designed in KiCAD, that includes custom footprints for vintage elements. All design files and source code is available on GitHub.

My explicit goal was to include many vintage components, each of them has its own backstory. After many years I still remember the way I came into possession of some of this stuff. When I do, I put notes in appropriate places in the description.

Power supply

The device is powered by transformer, which provides two voltages: 24 V and center-tapped 5 V. The second winding was wound by me by hand in order to power the VFD filaments. The main board contains the power supply circuit, more about this in the article.

Transformer comes from an old medical device I have torn apart as a child.

The device draws its power from 230 V 50 Hz mains. I used braided cord from an old iron. The mains side is protected by lighting arrester RB-5. It might be an overkill, but the glass envelope sure does look cool, doesn’t it? As you can see in the photos, military socket is used for power.

The transformer generates 24 V, which is routed to the front display board. I used braided wires for power distribution within the device. As I said previously, I had wound additional center-tapped 5 V winding for the VFD display filaments. I did it in the following manner. First I wound ten turns and measured the output voltage. Then I calculated the required number of turns for 5 V. It was about 30. It was quite tricky to wind them without disassembling the core but achievable indeed.

Some of the wiring within device is done with magnet wire insulated in double layer of cotton. The wire comes from an ancient generator from 1920s. This generator used to serve as an electricity source in the mill located in my father’s home village. He has obtained it in some murky circumstances. This way, I’m using hundred-year old wire in my plaything.

24 V AC goes to two circuits on the main display board - voltage doubler for providing supply for VFD anodes and step-down converter to generate system voltage 5 V DC. There is also 3.3 V stabilizer. 5 V and 3.3 V are available on the system bus.

System bus

All modules are connected by 10-pin IDC cable. It provides supply voltages: 5 V and 3.3 V and also I2C bus. The exact pinout was inherited from one of my previous unfinished projects - therefore three unused pins. The pinout itself:

System bus pinout.

Indoor weather sensor BME280

Encased in fancy cylindrical case made of RF coil shielding with holes drilled. The main purpose of the case is to shield the modern look of BME280 from the viewers eyes, so it does not disrupt the vintage feel of the device.

BME280 is an integrated temperature, humidity and pressure sensor. It is widely available as cheap Chinese module, which also has voltage stabilizer and I2C level shifter. However, these particular modules are low quality. In the end I decided to skip measuring humidity at all since it failed to bring me accurate readings.

The Chinese module I used sets the I2C address of the module to 0x76.

External I2C socket

The device has external 4-pole DIN circular connector with following pins:

During development I run the octoglowd software on the PC and controlled the device through USB to I2C converter. At first I simply connected to I2C line on VGA port. However after changing graphics card on my PC from ATI to nVidia VGA was no longer available, furthermore I2C on HDMI failed to function correctly. I tried other solutions but stayed with Digispark module flashed with i2c-tiny-usb firmware. In my experience this is the most convenient I2C to USB bridge. It is supported in Linux kernel directly so I use exactly the same software on the PC and on Orange Pi Zero.

Octagonal skeleton chassis

The skeleton is made of 15 mm rectangular pipes. In some of the photos you can see that wielding is not completed - the skeleton was barely wielded by me just to hold the shape. After the development process is finished, the remaining job was done by a professional.

Dimensions are as follows:

The skeleton is made of two parts joined by four M6 screws. You can disconnect them to access the interior.