原创 Designing a Nixie tube speedometer (Part 1)

I am into all things digital. When I was a boy, my dream was to make a Knight Rider-style dashboard. That would have looked so cool on my bike, but I don't think I would have been able to steer the thing.

Unfortunately, parts from RadioShack were always too expensive, so I was stuck building a drastically cut-down version featuring only a single-digit counter. This was based on the classic 555 timer driving a decade counter, which fed into a BCD (binary coded decimal) decoder, which drove a 7-segment LED display. (The Back to the Future dashboard was also really cool—I'm still looking for an excuse to build one.)

The reason I mention all of this is to make you understand why, when I eventually purchased a 1953 International Pickup Truck, I looked for a reason to make it digital.

As you can see from the image below, the original speedometer left something to be desired. On the other hand, 7-segment LED displays do not belong in any automobile from 1953!

This is where Nixie tubes come to the rescue; they are so vintage-looking and bring a warm fuzzy feeling to the party. This was the reason I decided to design and build a GPS-driven Nixie Tube speedometer. Using a GPS unit means I do not need to hack into my speed cable or cobble Hall Effect sensors and the like together to determine speed.

This project uses the parts shown below. You can substitute as you would like, but here is what I ended up with just out of convenience:
* One High-voltage DC 115 to 235V Nixie Tube Driver ($18 on eBay)
* Two K155ID1 Nixie Tube Drivers ($2 each on eBay)
* Two Nixie Tubes ($10 each on eBay)
* A PmodGPS GPS Receiver ($45)
* A Basys2 Spartan-3E FPGA Board ($50)

You can find cheaper GPS receiver modules and you can make your own DC-DC converter. Furthermore, if the FPGA design is implemented carefully enough, we will probably have the option to squeeze it into a CPLD if we so desire.

In my next blog I will walk you through the design and construction process, show you a video of everything working, and provide access to all of the design files (note that this project works with high voltages—so be careful!). In the meantime, I welcome any questions and comments.

Luke Miller

Independent Contractor