Before my IN-14 clock
, before my IN-12 clock
, I wanted to make an IN-18 clock. I built the IN-12 clock just to use up the nixies. I bought them 10 years ago not knowing what I was getting myself into. I built the IN-14 clock because I wanted tubes that stuck out of the top of the clock, instead of being mounted on the front like IN-12s. I really wanted IN-18s, but they are so damn expensive!
When my wife asked me what I wanted for Christmas, I didn't hesitate: IN-18s. Six of them. She asked how much was that going to cost. I told her they were expensive; like $50 bucks a piece. She looked at me and said, "So like, $300 bucks?". I said, "Uh huh". She looked at me for a second, shrugged her shoulders and said, "OK, go buy them." Best. Wife. Ever.
They came all the way from Ukraine, so they did not arrive in time for Christmas; despite ordering them on December 9th. They arrived a month later.
I was so thrilled when they did. They are perfect. Mint condition. They have a late date code: 1988. So in the grand scheme of things, they are relatively new.
Massive! They dwarf the IN-12.
Minifig for scale.
The first order of business is to design a breakout board for them so that I can do some prototyping. I'm sure you're thinking that I could just dive right in and modify my IN-14 clock to make them fit, but not so fast! I drove the IN-12s with some 74141 nixie driver chips. Those will not work on IN-18s. That's because when digits are off, they can still draw enough current to cause a nasty blue dot to appear. The best way to drive them is with some shift registers and some transistors.
I'm going to have to play around with some stuff to figure out exactly how I want to drive them. If I use transistors, I'm going to need 60 of them. Maybe I can use some kind of high voltage chip and forgo the transistors altogether.
I hopped into EAGLE and put something simple together.
It's nothing fancy. I just broke the pins out to a header so that I can breadboard them and put in a spot for an anode resistor.
Looking good. I then sent the boards off to be fabbed.
The wait begins!See this project from start to finish:
IN-18 Nixies TPIC6B595 Shift Registers IN-18 Nixie Clock - Part I