Congratulations on acquiring 6 NIMOs !! I've gone thru all the NIMO filament analysis and came up with the following, which I have implemented in my design
1. Transformer is 2.5V CT, 3A. Triad F301X.. It has dual primaries so it can operate on 115 or 230 VAC mains. 2. Series fuse 250mA (BEL C1F250). One for each NIMO 3. Series resistor; empirically I'm choosing 6.8ohms. The filament is the most-critical reliability-impacting element of your NIMO tubes, so be extra careful to make sure you design with this in-mind. Filaments usually fail due to power-on surge-current, just like conventional incandescent bulbs. The surge-current is the result of the lower-resistance of a cold filament being the only limiter of current. For example, measured NIMO-tube filament resistance varies from about 2.8 ohms cold, to 7.0 ohms when stabilized at 200mA. If you use a constant voltage to power the filaments, you will have significant surge current. But if you add some series resistance and drive from a higher supply voltage, the surge current will be less. With the components I listed above, the surge current is about 260mA. The fast-blow fuse will protect the NIMO from line-surges, or other uncontrollables. I'm almost done with my NIMO clock, and I will collect waveforms of the power-on transient for each filament once I get my other tubes (I have 1, need 5 more) -- 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 post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/c339f697-a724-42ad-9049-7cefda484742%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
