Your clock is the first practical use I've seen for these tubes. I bought a set of six years ago, if nothing else for their uniqueness.
I would be most curious to know what their intended purpose was - why would they design a display tube that had such odd power requirements. Perhaps on the plus side, is it's a high-voltage tube that can be controlled directly with TTL logic (if I understand other references I've read). Joe, N6DGY :28 AM UTC-6, Arne Rossius wrote: > > Hi, > > I saw some talk about the ITS1B thyratron indicator in the archives, so > I thought I'd share my clock design I did a few months back. I got the > tubes from ebay for about 15 Eur each (it looks like they have already > doubled in price by now). > > There is a russian datasheet available for these tubes at > http://www.tube-tester.com/sites/nixie/dat_arch/russian-book-0001.djvu > (starting at the bottom of PDF page 211, original page 210). After > having some fun with Google Translate's on-screen keyboard (I don't > speak russian), I figured out that these voltages are required: > > 1st anode: 40V ± 4V > 2nd anode: 100V ± 10V > under-cathode: -250V ± 15V > > I also found that the current on the first anode is negative, so > clamping it to ground with a 39V zener diode is sufficient. > > To reset the fired segments, the 100V power supply has to be > disconnected for at least 500 us (I used 1 ms). The shortest pulse to > fire a segment (on the 5V CMOS compliant grid inputs) has to be 100 us > (I used 1 ms as well). > > As expected, the power supply was the most difficult part of the design. > I used the UC2843 fixed-frequency (PWM) controller IC for the 12V to > 100V step-up and connected a voltage multiplier circuit to to switch pin > to generate -300V (since the main output is 100V, it is impossible to > generate the required -250V directly through a multiplier) and used a > resistor + zener diode circuit to drop the voltage down to about 250V. > The current draw on the under-cathode is pretty constant, so just a > resistor with a carefully chosen value probably would have been good > enough, but I wanted to be on the safe side. > > Due to the load on the switch pin, the power supply was very unstable, > especially when only drawing current on the -300V output. I finally > managed to get it stable in discontinuous mode, when in continuous mode > there would always be subharmonic oscillation (a few short pulses > followed by a long pulse or vice versa on the gate drive output, causing > audible noise). I fiddled with the operating frequency until I managed > to get the full current without the power supply entering continuous > mode at about 30 kHz. The timing capacitor value is rather critical, if > you use my design make sure to use a low tolerance cap here (definitely > not ceramic) and measure the frequency at the gate drive output. Also > use a beefy enough inductor (my first try with an axial resistor-style > 1.5mH, 6.5R inductor failed miserably). > > I uploaded my files here: > http://elektronik-kompendium.de/public/arnerossius/temp/its1b/ > It's all there: schematic, PCB layout (both as PNG and EAGLE 4.x files), > a scan of the partially translated datasheet, the code for the AVR > microcontroller, some photos and oscilloscope screenshots (in the "oszi" > directory, ch1 = switch pin, ch2 = -300V output). > > The AVR program is for use with the German DCF77 radio time transmitter, > but it should be easy to modify the program to be used as a > quartz-controlled clock (using PD5 and PD6 for the set buttons) or even > write a new one from scratch. > > > Best Regards, > Arne > -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/35d3aa94-1798-4467-94a7-8bc5bce0fc8a%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
