Using DC for the filament means there is more accelerating voltage at one end than the other and results in a noticeable difference in brightness.
I have wondered if it could be solved without a transformer by driving the filament with a h-bridge. On Wed, Sep 14, 2022 at 9:02 AM Richard Scales <[email protected]> wrote: > Hello everyone, > I have just managed to acquire a set of these and would ideally like to > drive them the best possible way. > I had initially though about a 5V for the filament and then 24V for the > cathodes and grid. > The clock would only have segments activated when someone is nearby - the > segments will not be left on all of the time. > Now I read about A/C supply to the filaments and wonder if I should be > going that way. > Would anyone be able to post their findings and/or suggest the right way > forward? > [image: VFDsnip.JPG] > > I just noted that the picture above shows the connection for the grid (pin > 9 on H1) connected to 5V and not the 24V as used on the cathodes. > The more I think about it - the less clear this all becomes! > I need to get it right in my head before I go breaking something and then > I would like to get the best possible result via reasonably straight > forward means. > Would anyone be able to point me in the right direction and/or share > proven drive methods? > - Richard > > > On Monday, 16 September 2019 at 22:23:47 UTC+1 gregebert wrote: > >> Yes! That's exactly what happens. The current through the center-tap is >> the sum of the anode (segment) current and the grid current. And the peak >> current through the filament wires is actually *greater* than just the >> current to heat the filaments. >> >> >> *Tomasz* - As you found out, those VFDs draw a lot of current. I have a >> future design for a 6-tube ILC1-1/8 (smaller tubes than the ILC1-1/7) and >> I'm just going to use a high-current filament transformer with the >> center-tap at GND. Grids will NOT be pure DC; closer to full-wave rectified >> around 15-16V. Segment anodes will be pure DC around 36-40V with >> current-regulators and non-multiplexed. >> >> I actually have an Op-amp summer+ADC+Software to monitor the current thru >> the center-rap on my NIMO clock to determine the tube health, though it's >> orders of magnitude smaller (30uA per tube). >> >>> -- > 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 view this discussion on the web, visit > https://groups.google.com/d/msgid/neonixie-l/88406a7a-3854-4dc2-bf24-8a33f769811en%40googlegroups.com > <https://groups.google.com/d/msgid/neonixie-l/88406a7a-3854-4dc2-bf24-8a33f769811en%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- 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 view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/CALiMYruQ0Qbm741UYeurekUGAPWVPU_GnTYCHurMpfO1odi0_g%40mail.gmail.com.
