Retro Temp

Sascha Grant

Issue 4, October 2017

Digital displays might be the standard these days, but there's something special about the classic Nixie Tube.

We took a quick peek at Sascha’s Nixie Tube Temperature Display, in our Community Submissions section of Issue 1. However, it received so much attention that we thought we should share the full story with you. So we spoke to Sacha about this fascinating application of Nixie Tubes.

How did you get started with Nixie tubes - have you used them before?

I discovered Nixie tubes a little over a decade ago, and thought they were very cool (that’s a cold-cathode joke!).

You can see my first clock on my flickr stream. It was built sometime prior to June 2006 and used a pre-programmed uController that I purchased from Neonixie.

The full harness before it was mounted into the case.

Where did you get the Nixie tubes and driver from?

The Nixies and drivers actually came from the Ukraine via eBay. There’s always a good selection of tubes available, and so far I haven’t had any problems with postage; you just have to be patient as international post from Europe can take a month or so!

Prototyping the system.

Did it take much experimentation to get the prototype running?

There were a few steps I went through in putting the prototype together - I’d never dealt with the DS18B20 1-wire temperature sensor. I started by installing the Arduino library and playing with the demo code. Once I had the temperature displaying correctly in the console, I moved to driving the Nixies.

First step there, was to get a single digit running; just ticking over numbers sequentially, making sure that I had the Soviet K155ID1 Nixie driver IC wired correctly.

The prototype only ever got two digits installed, but from memory, I had the prototype running correctly over a few evenings after work.

Are you using a DHT sensor, or something else for temperature measurement?

I’m using the DS18B20 1-wire sensor in the TO-93 package, which looks just like your garden-variety transistor. The original intention was to have the sensor sitting just proud of the housing, but I discovered that the heat generated in the case runs at about five degrees above ambient, which meant I was getting incorrect readings. So I ended up moving the sensor about 10cm from the case, by using a short length of ribbon cable that was covered in heat-shrink tubing. Temperature readings are now pretty much spot-on with the comparisons I’ve done.

Yes we’re getting used to displays not putting out much heat - that’s an interesting point! How is the whole unit powered, and what’s the power consumption overall?

A 9V 500mA power supply provides power to the high voltage circuit and the Arduino. I’ve found that the Nixie power supply produced by LEDSales is stable and reliable. In fact, this is the same power supply that runs my original Nixie clock from 2006 - providing more than 11 years of service!

The Nixie tubes run at approx 180V and around 2mA. The Arduino Pro Micro that I’m using is 9V tolerant.

Not really much at all for something that looks so amazing! Your laser cut case is great - what laser cutter are you using?

I bought my laser back at the end of 2009, to support my Model Rocketry hobby. I purchased it from WKLaser in China and learned more about importing, customs, quarantine, duties and paperwork than I ever thought I would! But by importing it myself (with the help of a freight agent), I saved a substantial amount of money in the process. The laser has a 60W CO2 water-cooled tube and a cutting area of 400mm x 600mm. You can see photos of this on my flickr stream.

Sascha made a fantastic laser-cut case to mount everywhere into.

At least you’re putting it to good use! Did this project inspire any other Nixie-based projects?

I’ve built a few Nixie projects prior. I have a “people counter” that’s still a work in progress. I’m the president of a maker space called MESH (Melbourne Eastern Suburbs Hackers), and I started building this to take along to maker fares and events like the Stringybark Festival (in the Knox Council area), for people to interact with. Like many projects though, I’m still tinkering away on it!

We often have as many projects on the go as we have completed! If you had your time again, what would you differently for a V2.0 of this project?

Oh, that’s easy! Nixie tubes have a finite lifespan and there are some techniques used to maximise their life. So the first thing I’d do for version 2 would be to add an ambient light sensor, which would automatically dim the Nixies when the light in the room drops, and I’d add a “slot machine” type effect to cycle through all the digits every few minutes.

Both of these additions would boost the visual appeal and increase the lifespan of the Nixies.

I’d also love to build a wooden box to house everything; maybe in a lacquered walnut or something similar, as I feel the acrylic is a bit cold and the tubes would look much better with a nice warm timber surround. Maybe one day I’ll try my hand at woodworking!

The display is bold, sure to capture attention.

At least you have a plan! Increasing the lifespan is also a valid point - not something we really think about with an LED display (obviously). What are you working on now?

I’m currently focused on a Bartop Arcade Machine using a Raspberry Pi and 10” display. I’m a bit of a retro gamer and have seen some absolutely fantastic looking machines on the internet. I’ve got all the parts now sitting there, just waiting for me to dedicate some time to start.

Sounds awesome - we can’t wait to hear about it in the future!