Dave Cooper's Nixie Tube Page

Hello.

Welcome to my nixie tube clock page. Questions? Comments? Email me at dave@kupesoft.com.

Stuff that I've authored

• My high voltage nixie PSU is an AVR-based DC-DC boost converter.
• Here's my most recent (r3.0) nixie clock schematic and circuit board (I've included most of the fixes from the older schematic below).

Older items

• Here's an older nixie clock schematic. This schematic had some minor problems but most are on the board which I won't release. Note I've deployed this and it seems to be running fine. Here are some issues that I identified:
  • There should be a ~100k pull-down resistor on the MOSFET gate. When the PWM'ing pin on the AVR that controls the gate is high and then is set to high-Z, current flows unrestricted from 9v (or 12v) to GND through the MOSFET. Shorting, the MOSFET gets extremely hot having less than an ohm of internal resistance, maybe frying, maybe causing a brown out. Definitely a problem. It's only an issue when flashing code, in the bootloader after a reset but not at power-on, or when the reset button is pressed and held at the wrong time. These are corner cases and I've got a software fix for now.
  • I was told in ##electronics on freenode that I need a 120-150 ohm current limiting resistor on the MOSFET gate. If I understand correctly the reason for this is that the MOSFET's gate is an inductive load and every time it's pulled high or low the AVR experiences a tiny short that's potentially damaging in the long run. I'm a computer scientist and this is over my head. I've seen designs where other people don't use such resistors. Maybe the solution is a FET driver. For now, I'm not changing this.
  • The nixies aren't labelled right. Nixies 1-4 should be wired to driver IC5 and 5-8 wired to IC6. Oh well.
  • Even at ±20ppm, the RTC's 32.768KHz crystal drifts -- especially in an enclosure with poor air circulation and parts like the 7805 shamelessly dissipating heat. You could try something like the DS32KHZ as a drop in crystal replacement for your design.
    • I'm generally afraid of surface mount parts, but I used the DS3231 on my next generation board above. Here's a CadSoft EAGLE library for the DS3231 that I've written.

Photos

• Our first prototype made from a 3D printer.
• We're doing a series made out of black conduit pipe and IN-1 nixies: one two three four five
• The most recent circuit board (r3.0) mentioned above with the LED and R21 absent. Also, here's a blurry picture of the first nixie clock board that I designed. It had a 555 timer based PSU and never saw the light of day. Designing it was a good learning experience, though.

Links and things of interest

• derivative clockworks -- Want to buy one of our clocks?
• Greenwood Studios -- Woodworker we've teamed up with. Come back late January or early February 2011 for updates on the project.
• ArduiNIX -- An Arduino shield for nixie driving that I'd highly recommend for beginners.
• NEONIXIE-L -- A Google group for discussion of all things nixie.
• BatchPCB -- A great and relatively cheap single or small run PCB fabricator run by SparkFun.