Very cool project... inspired me to get started on a nixie clock a few days ago. I gotta tell ya', making these things from scratch is a real challenge... After scouring over online schematics I just ordered a ton of MOSFETS, schottkys, inductors, HV caps, 25 MPSA42s, etc. from digikey only to realize that to multiplex tubes I also need HV PNP transistors. :o
I'm also using way too many transistors, right now with my current schematic for only four tubes I'm at all 25 MPSA42s, 4 MPSA92s (anode switching), 14 general purpose switching transistors, and total of 13 IC pins just to switch the tubes (not including the pins of the ATTiny45 controlling the high voltage PSU).Kudos to you for making a very clean, non-parts-intensive build (albeit with the help of some control ICs :P).
I don't do any multiplexing, so I'm just using 3 anode resistors, 4 155id1 (= russian version of the SN74141) and 3 4017 binary counters. I drive them directly, because the tubes are brighter this way and I actually need less power because the firing of the tubes is pretty expensive power-wise.
I need the extra 155id1 for the decimal point on two tubes that is driven separately from the digits. I just need two outputs from that driver so I get along with two inputs. Switching on the digit one from this driver lights a decimal point before the second digit and the two is a decimal point in front of the third digit. I also could've wired the point on the first nixie, but I decided that something like .845 would look weird and 0.85 is precise enough for this application.
I also used a prebuilt power supply to get the 180 Volts (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=140426808956) once I realized that you have to be very careful on placing the components on the converter to get an efficiency over 80%.
I can highly recommend this, it's not much more expansive than buying the components (Unless you order the MAX1771 that you need as a sample), it's tiny, works perfectly and can be switched off completely via the arduino.
Some comments on power:
With all three tubes lit the circuit draws 500mA and under 100mA without them. The tubes light for about 10 seconds per distance fix and it needs about 60 seconds to get the fix. So there's an average power consumption of 200mA.
The batteries (NiMH D-cells ) have 6000mAH but because of the voltage drop I'm just counting them in for 3000mAh.
That should be enough for 15hours continuous operation, or at 90 seconds per fix, 600 fixes which is enough to find the target coordinates.
[edit]
PS: This is where I got the tubes and driver ICs from: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=250749058503, they also come with nice pins that you can solder to a board to make your own socket.
In case the auction is gone when you read this - this is the seller: | eBay . The tubes are called IN-12b.
[/edit]