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.
