Thursday, March 1, 2012

NTP Nixie Clock

So I have been chugging away on my design for a Nixie alarm clock, but first decided to make a Nixie clock that could communicate over the network. What better functionality to add, than syncing via a NTP server. I am not a fan of reinventing the wheel. So I am basing my design on one I found already. I found someone who had previously done this project: see here. I noticed he based all his coding, etc. off of NTP synced LCD clock, who has a nicely implemented TCP stack they have posted under GPLv2 (I looked around for the original source, but was unsuccessful for now). The schematic after being put together looks something like the one below.

Essentially, this takes a 9V wall wart and turns it into the +3.3V & 5V needed to run the ATMEGA and the ENC28J60 Ethernet chip Then, as is standard for most Nixie drivers, it uses a 555 timer and a discharge capacitor to drive a switched 180V DC line. As is also pretty standard, it uses two 74141N drivers to actually drive the cathode of the tube itself. These chips can handle being connected to the relatively high voltage Nixies.
The anodes are driven by a simple series of step-up transistors hooked up to 3 output pins on the IC.

The Ethernet chip is very well documented, and is hooked up according to the datasheet, nothing too fancy there.

At the bottom of the site linked above, the code is available. It essentially is a replica of the Tuxgraphic NTP clock, with the driving of the LCD screen changed to be the driving of the Nixie Tubes. There are a few things I am going to change in the program, if I don't end up scrapping it altogether. I don't want my clock having a static IP address. I also think I will have it update my time more often via NTP. I do like the idea of displaying a date and having the cathode poisoning.

First attempt at making the clock DHCP: It worked, HOWEVER, it made the resulting binary about 35% too large to fit on my ATMEGA168, and that wasn't even with NTP updating added in.

On a last note for now, I did get the board designed in EagleCAD, and sent off to get prototyped. Hint: For $35, I was able to get 8 professionally produced boards. If they turn out ok, I might even hold off on my research of UV LED PCB Etching.

For now, project is on hold until I get in my 74141 drivers (ordered 3 weeks ago, so hopefully soon). The good thing is, all the changes I want to make to this are in software, so it will be easy to change as time goes on. Unfortunately, I am probably going to have to upgrade to a 328 too get additional flash space if I want to go much further with this iteration. But only time, and some fancy coding will tell.

1 comment:

  1. Hi Markk !
    I am also reproducing this Nixie Tube Clock for a special project.
    Do you thing you can shared your EagleCAD file ? it would be much appreciated !

    Thanks in advance !