Adding series resistors also reduces the current spike during power-on. Hard to say what fails first with VFD's; ones that I've seen such as the displays on kitchen appliances which run 24/7 show phosphor degradation after a few years. If you frequently power-cycle the filaments, then you definitely want to take steps to reduce the current spike.
Be sure to include a PIR sensor so you can shut off the segments when it's not in-use; your decision to keep filaments on or off. For my NIMO clock, I shut off the anode supply after 2 minutes of no PIR activity to reduce phosphor burn, and the filaments go off after 12 hours of no activity. On Friday, June 16, 2023 at 6:20:18 AM UTC-7 Paul Andrews wrote: > Assuming you drive the filaments in parallel rather than in series, a DC > voltage would be fine. If you drive them in series then (I assume) the > voltage gradient might be visible. A decision to drive in parallel has a > knock-on effect - I couldn't come up with an AC drive that had a constant > voltage with varying load. With filaments in parallel, the load will change > if one or more filaments burn out. You don't want a filament burn out to > increase the voltage across the remaining tubes, otherwise they might burn > out too - so a regulated DC voltage is easiest. With a non-regulated AC > supply, you will also get a higher voltage at startup when the filament is > cold. Another reason to go with a regulated DC supply. Which brings me to > the potential issue of in-rush current. Either a constant current setup or > a current-limiting resistor in series with the filament would be a good > idea. The latter also helps with achieving a voltage offset to the grid - > i.e. making the grid negative with respect to the filament. > > On Friday, June 16, 2023 at 1:45:02 AM UTC-4 Richard Scales wrote: > >> Greetings all, >> >> I am starting to look at VFD displays and am reading all I can about them. >> >> I am trying to get a better understanding of the pros and cons of using a >> AC filament drive rather than an DC one. >> >> I am aware that on larger displays (like those monster ones from Russia) >> it is necessary in order to create a more even glow across segments. I >> wonder however how important this is for smaller segments like those in >> IV-22 for example. >> >> Making the filament drive AC adds a small degree of complexity but if the >> difference is visible and beneficial then I'd like to go that way. >> >> My project would be direct drive, no multiplexing required. >> >> Any advice would be greatly appreciated. >> >> - Richard >> >> >> -- 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/b863697d-2ec5-47f6-b57e-67a22b09573fn%40googlegroups.com.
