Sorry for not being helpful, but I'd love to see your digivac clock when you're done!
On Fri, Aug 20, 2021, 12:58 PM Paul Andrews <[email protected]> wrote: > I'm designing a clock for DT-1704 tubes and am stumbling at the filament > drive stage. They want 1.6V. I want to power it from 5VDC. I've tried > wiring them in series, but there is a noticeable brightness gradient if I > do. I've tried powering them using a LM4871 to generate a square wave with > 1.6V RMS, but the voltage drops as I add more tubes in parallel (an aside: > why is this? I know it is specified to drive a 4 Ohm to 8 Ohm load, so I > assume that is it). I don't want to dump a bunch of heat through a LDO or a > stack of diodes. So I looked at making a buck converter. > > If at all possible I would like to re-use the design for other VFDs, e.g > for VFDs that want a grid to be pulled below the VFD voltage, and I would > really prefer to use AC rather DC so I can use it for multi-digit VFD tubes. > > I thought that if I made the buck converter output isolated I would end up > with a solution that would be more re-usable for different kinds of VFDs, > but naturally I hit the issue of what off-the-shelf transformer I could > use. I also got to thinking that the output diode of a buck converter that > produces 1.6V is going to drop a significant part of the total voltage, > which made me wonder why I should even try to rectify and smooth the output > given that an AC filament voltage would be better anyway. Then I also > wondered if such a solution would hit the same problem as the LM4871 > design, i.e. dropping voltage as I add more tubes in parallel. > > So I would appreciate any suggestions for what direction I should take > here. I have too many options and no clear criteria. > > -- > 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/860d4d78-c807-415e-a740-b576a4b5d18cn%40googlegroups.com > <https://groups.google.com/d/msgid/neonixie-l/860d4d78-c807-415e-a740-b576a4b5d18cn%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/CAPDJQ6CUnUP1zPbCkay%2BYO_YbcWx0eK7BTaETfRA9OroiHUn6g%40mail.gmail.com.
