On Sunday, 16 April 2023 at 02:50:44 UTC-4 petehand wrote: I use H bridges for my VFD designs. The VFD heaters are designed to run as slow as 50Hz, as the thermal inertia is more than sufficient for a steady display. There will be no beating. I generally run them at about 200- 500 Hz. The bias needed is negligible, just enough to make the anodes slightly negative relative to the heater - 1 volt is usually plenty. It is, as you say, equivalent to half the P-P AC voltage.
What is your strategy for biasing, are you pulling the anodes negative or are you adding a DC bias to the filaments? I'd prefer not having to have a separate negative power supply so a positive bias on the filaments is ideal, but I'm not sure how to DC bias the h-bridge, I'm imagining a zener at the h-bridge ground would do it? I guess the problem is my H-bridge is an integrated IC, so it's Vout ground and digital ground are tied, adding a zener to the IC ground might mess with the digital logic. I tried adding a zener for my transformer to bias it and it seems to work here with a simulated 30V grid being turned on: https://www.falstad.com/circuit/circuitjs.html?ctz=CQAgjCDsB0AcYCYCsBTAtLEAGaBOWuYALFrgGwDMFRSSkSZIuuISrWr6YYAUAG7hE4Mh24IQRTB3FgscudjiKpipP0HiKZTGJDJG08PIU4pSitGJgkuBGSQUkBSLgqqeAcw3DRQsLexsT28tHSESDkieAHdvSXAA+KweACdWBB0M9J0AjhIeMDIWBBJwLIiylRx5WWY6+oaWMGhSAixato7MNBwwWEgiWooXBApiGkUESCo+2DpcSCxqMchFLFgsMmsELEg2rFHcNhxmGIkFf3EiMiIE8WTYisK8ihkRIMfXnwkvnalgohfRxXIGwW5RR43O7ZaEPGGXViQRgIuF0ZFZJBZRD-WJoyogESZHHQ+IlPLE3T6PSlKlwsl6BjU0S5M54hGE2FnDnsxkornrfH2dHE+mk0rYoJpNkYpGw86pAkCiXc3LytJCwW81X5R4XDFYrLJaggABeKAAdigUmgILboJBiMD4LZ4PIEOhVtIWsYfcYweBwDwTT9xFMQaGBeIzZbrbxhi9Q5BwyBgQGomkKvEnkIOBQ5DwAEoprQSTBURg2gyBUp5wKRaBqAAOUB2+KT0hrdeC7aZLekSa7sQ1Ep7EuSAGdzuTi4wkoEAGYAQwANuOUGdM5hrrckgrt6WJFDdLn85Dbrp93zdb4rnr-gB7QIQURIay0VjKQL3FM8R9sZ96FgkhuLIkwBuIbBuAAYgAlsui4ALYWgALr+H4QKsYCOGA9Afr0ehptAZDIGhtYASQ+BGIoEAgSAABCMGLmuAAmAA644AGpoPOcGIShaFTGm4DYUUazyEiCCuLgNBjMg4BERIBGCW4DFMWgADGACuKQpPxQA A DAC with an opamp buffer on the center tap would be interesting, but wouldn't that opamp be taking a lot of current with some larger VFDs? -- 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/340799fa-9193-42c5-8c24-205b3642f9e4n%40googlegroups.com.
