Re: [neonixie-l] VFD Filament Current
VFDs are basically directly heated triodes. To reach cutoff, the grid has to be at some negative potential in respect to the cathode. It is just easier to elevate the cathode above ground and swing the grids to ground than creating yet another voltage rail. The question is - if the filaments were heated by a transformer with center tap connected to, let's say, 5V, would there be any current flow from or into the 5V rail? The grid + anode current has to go somewhere, after all. It might mean that the elevated voltage has to be low impedance, and most likely - it has to be able to sink current, which standard linear regulators can't do. This is something that concerns me, as I own four ILC1-1/7 and plan to make a clock out of them. Their anode and grid currents are dominant compared to any other circuitry. W dniu sobota, 14 września 2019 14:22:36 UTC+2 użytkownik Paul Andrews napisał: > > Papers I have read also emphasize the need to bias the filament above the > cutoff voltage of the grid or anode, so I assume if the center tap is > attached to ground, that the cutoff voltage of the anode or grid is > significantly below that? In fact it would have to be below the negative > swing of the AC. It might be easier to connect the center tap to a positive > voltage? See the diagram in the "Cutoff bias voltage" section here: > https://www.futaba.co.jp/en/display/vfdinfo/vinfo_kudo_1.html -- 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 view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/5050bdef-b0ce-4ddf-a281-4f9aaf277152%40googlegroups.com.
Re: [neonixie-l] VFD Filament Current
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 neonixie-l+unsubscr...@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/b3c45b79-e626-49e7-a110-7706953acbf3%40googlegroups.com.
Re: [neonixie-l] HP clock wow.
Here's a manual for it! https://www.ebay.com/itm/HP-Hewlett-Packard-59309A-HP-IB-Digital-Clock-Operating-Service-Manual/391791021156?epid=1462831819&hash=item5b38908c64:g:WiYAAOxydB1Sk9jC On Sunday, September 15, 2019 at 6:55:26 PM UTC-7, Kevin A. wrote: > > Wow. From the days when HP actually engineered high end products... > > On Sun, Sep 15, 2019, 9:47 PM Bill Notfaded > wrote: > >> http://www.hpmuseum.net/display_item.php?hw=741 >> >> -- >> 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 neoni...@googlegroups.com . >> To view this discussion on the web, visit >> https://groups.google.com/d/msgid/neonixie-l/e5de72ee-0a24-47af-8aeb-da780e422736%40googlegroups.com >> . >> > -- 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 view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/29c964a6-8c7e-4488-a506-dceba743e489%40googlegroups.com.
