Nixie Clock project files - PCB and source
I have to start by giving credit where credit is due. The Boldport Club, over the last couple of years, has motivated me to dwell back into the world of electronics, at least as a hobbyist. Both the kits themselves and the other members in the club are amazing and helped inspire me to make something...so I began working on this project. Some inspiration is taken from Touchy, BPC Project #7; this kit enabled me to learn more about and actually experiment with capacitive touch. It was clear early on that this would be a nice touch (pun intended) to add to this project; visually, it is cleaner, it reduces the number of parts and, as a result, it reduces the cost.
That said, the world probably doesn't need another tube clock. There are plenty of them--all different shapes and sizes--so why build another one?
Last year, I built this lovely binary clock. Some ten-plus years ago I had built some IN-18 nixie clocks. Earlier this year (2019) one of them became a little troublesome. I fixed it but, in the interim, became motivated to build my own. As I already had a wonderful foundation for some clock hardware, this seemed a natural progression. Overall I'm quite happy with the results if I may say so myself. :)
Sooo...another nixie clock? What's special about it?
First, I brought the touchkey design over from the binary clock. That seemed like a no-brainer. Still, it needed more...flair. Soooo...let's get the time from GPS -- either a soldered-on LIV3F module or a more friendly module from Adafruit. How about an infrared remote control so you can turn off the display from across the room while you're watching a movie? Or rather, if you don't want to do that, it'll still do that cool display-dimming thing that I did with the binary clock. These tubes can be pretty bright in a dark room. :)
Also, just like the binary clock, it can do more than just tell the time -- it'll tell you the date and temperature, too! There is even a timer/counter mode. What's more, you can choose the format for it all: the clock can display in a 12 or 24 hour format, the temperature can display in degrees Celsius or degrees Fahrenheit, and (most importantly) you are able to choose the formats you prefer and they can be changed easily at any time.
As mentioned above, it has a phototransistor which is used to determine the amount of ambient light around it and the display will dim smoothly as the light level around it diminishes. This is great if you want to keep it near you at night while you sleep.
A CR2032 coin-cell battery backup can be installed to keep the time valid in the event that the board loses power; there is also a super capacitor, eliminating the need for the battery; even so, both can be installed, adding flexibility to the build.
Finally--and one could argue that no clock is complete without one--it has an alarm! The alarm can be set to beep at any of the eight times the user sets. There is also an hourly chime that one can enable which will beep out each hour in binary using high and/or low pitch tones...so you can hear the time when you're in another room! The display can be configured to blink when an alarm occurs. Finally, unused microcontroller pins from the STM32 are brought out to a pin header, some pins of which can be used as inputs to trigger the alarm from an external device -- or connect other hardware of your own!
The "brain" is an STM32F072 microcontroller. This MCU alone has everything that's necessary to have a functional time clock -- even a temperature sensor as a bonus. Still, it might not be quite as accurate as some of us would like. For those folks, there are footprints for some additional ICs to improve the accuracy of the time and/or temperature sensing:
- A Maxim DS3234
- A Maxim DS1722
- A LM74
- A LIV3F GPS module (and associated antenna front end with several 0402 parts!)
- A header for an Adafruit module
Why footprints for both temperature sensors and the RTCs? The DS3234 is somewhat expensive and it's possible that one might want more accurate temperature sensing abilities but isn't as concerned with the accuracy of the clock. It should be noted that the DS3234 devices have temperature sensors built in and the application will use this sensor if a DS3234 is installed but one of the other external temperature sensors is not.
Beyond the MCU itself, the display boards have up to three (depending on the tubes/board) HV5622 high-voltage driver ICs on them to light up the beautiful tubes. The MCU uses its SPI1 to communicate with these drivers. There is a single RGB LED is used as a "status" LED and it is connected (through FET drivers) to GPIO pins on the MCU. These pins double as timer output channels, meaning they can also generate a PWM signal, enabling the dimming of the status LED elements, as well.
The beeper is connected (also through a FET driver) to yet another GPIO pin that doubles as a timer output channel; this enables the beeper to generate a wide range of tones or even play a tune!
The phototransistor is connected to the MCU's ADC channel ten.
Two USARTs are exposed via pin headers on the right side of the board: USART1 is brought out on a standard six pin header as is commonly found on many devices; it is also connected to the optional GPS module (solder jumpers allow easy disconnection of the module should it be necessary for troubleshooting). USART2 is connected to an RS-485 line driver enabling communication on an RS-485 bus. Through this interface, the application is able to receive a DMX-512 signal so the tubes can each be individually controlled from an entertainment lighting console (or other application that speaks this protocol), enabling another whole realm of possibilities...
In this repository you'll find everything needed to put one together. It is
divided into two major parts: hardware and software (source). The hardware
directory contains the KiCad project files used to create
the printed circuit board. The src directory contains the source code needed
to compile and run the application on the microcontroller. It is built on top
of libopencm3. Finally, then bin directory contains
compiled binary files you may flash directly onto the microcontroller...great
for folks who want to solder something together but don't want to be bothered
with compiling code!
Additional details regarding the hardware and software can be found in the
README.md files located in each respective directory.
That's all for now...thanks for visiting!