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 [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/d2fa02a0-32b4-46a8-a012-7e2996aa7478n%40googlegroups.com.
