The voltage applied to the elements of a Nixie tube is not as straightforward as you may think. Keep in mind that there is a voltage drop from anode to an 'on' cathode of ~130-140 volts, due to the ionized gas. Also, the capacitance of the tube elements and wiring has an effect on the switching behavior.
I have successfully made several varieties of multiplexed Nixie clocks and watches using 60V or lower cathode switches. I used printed circuit boards to reduce capacitance, and adjusted the timing to allow the recently turned off cathodes to drift up to their natural 'off' voltage before turning on the next digit's anode. My Nixie watch design uses 50V cathode switch arrays. It also has no anode resistor. This is done by enabling only one cathode at a time, leaving the other tube with no cathodes enabled. The power supply has a resistor current sense and feedback mechanism to regulate the total current as well as the open-circuit voltage. Blanking is achieved by reducing the anode voltage to 100V, with a digitally controlled shift to the regulator feedback. So you can get good results with very little circuitry, if you apply a bit of cleverness to the problem. http://www.cathodecorner.com/nixiewatch/firmware/nwrf-schem.gif On Sun, Mar 3, 2019, 8:54 AM gregebert <gregeb...@hotmail.com> wrote: > For direct-drive, you can just let the cathodes float, and they will be > completely dark unless your driver has leakage. I've done 5 full designs > with direct-drive that floats the cathode, and none has any issues. All > told, there are 52 nixie devices in operation with no hint of failure or > leakage. 24 of those tubes have been in service 24/7 for the past 8 years. > > There are some variations in the design, mainly for cathode and/or > anode-current limiting but they all float the 'off' cathodes. > > Admittedly, I've never done a multiplexed design with nixies, only with > LEDs, and unless the nixie tube is specifically designed for multiplex > operation I would stay with direct-drive. The reason I follow is that > multiplexed digits need a higher pulsed current to maintain visible > brightness, and higher current leads to tube wearout. > > > > > -- > 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 neonixie-l+unsubscr...@googlegroups.com. > To post to this group, send email to neonixie-l@googlegroups.com. > To view this discussion on the web, visit > https://groups.google.com/d/msgid/neonixie-l/e168a850-f3d7-4e88-adc8-1b3bd32b1902%40googlegroups.com > <https://groups.google.com/d/msgid/neonixie-l/e168a850-f3d7-4e88-adc8-1b3bd32b1902%40googlegroups.com?utm_medium=email&utm_source=footer> > . > For more options, visit https://groups.google.com/d/optout. > -- 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 neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/CAPbqtversF-P0-jzSGjs0iXvSz-skJagg8JV23DCxENt8Kae_w%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
