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/53A59EB6.6000402%40blinkenarea.org. For more options, visit https://groups.google.com/d/optout.
