I'm kinda in the same boat Paul... VFD's hasn't really been my thing but figuring out how to drive some weird ones is a new hobby. I love your questions because it helps me figure out what I'm doing as well!
Bill On Tuesday, August 24, 2021 at 12:57:53 AM UTC-7 Tomasz Kowalczyk wrote: > Did you try simple PWM? I once tried it, but didn't leave it on for long > time, so I can't tell if it shortens the tube life or not, but by simple > logic it shouldn't. For most of the time the cathode will be at the same > potential. Also it's a nice method of elevating the cathode potential above > negative segment/grid voltage to get rid of faint glow of off segments. > > poniedziałek, 23 sierpnia 2021 o 20:19:58 UTC+2 gregebert napisał(a): > >> Transformers are not ideal, so even with zero load, they consume >> inductive current. Most of the energy gets returned to the AC line, but >> some of it gets dissipated as heat (winding resistance, and hysteresis). >> This is why unloaded wall transformers still get slightly warm. >> >> You can measure the magnetizing current with multimeter. >> >> >> --------------------------------------------------------------------------------------------------------------------------------------- >> Be warned that large transformers will have a startup surge current; I >> have an isolation transformer in my workshop that can supply 20A/120VAC. It >> has dual primaries, so I can run it from 120V or 240V. If I try to run it >> from 120V, even with no load, it almost always pops the 20A breaker for my >> workbench. So, I use 240V and even then I can hear the wires in the conduit >> vibrate for an instant when it's energized. >> >> If you are worried about blowing the fuse in your multimeter when >> measuring the magnetizing current, it's good practice to use a variac to >> increase the line voltage starting from 0 volts into your transformer. >> >> On Monday, August 23, 2021 at 8:49:01 AM UTC-7 Paul Andrews wrote: >> >>> Thanks Martin, >>> >>> I'm OK with using a transformer. I would prefer something off the shelf, >>> but perhaps I should just wind my own anyway. Seems like a useful skill to >>> have. >>> >>> As with a lot of these things, I find that I have a lot of questions. >>> For example, this statement: >>> >>> "The transformer is 1:1, center-tapped. Since the output is to be 300 mA >>> max, the magnetizing current at the input should be no more than 30 mA. I >>> will try 10 mA" >>> >>> First of all, how does he get a 10:1 ratio of output current to 'maximum >>> magnetizing current'. Second, what is 'magnetizing current', does he just >>> mean current through the primary? >>> >>> Then he introduces terms in equations without defining them - they are >>> probably obvious to the initiated (which I am not unfortunately). For >>> example, Xl in L = Xl/2/PI/F and Al in N = (L*1e6/Al)^.5. Then having >>> calculated the required number of turns, he just ignores that and goes with >>> something much larger. >>> >>> On Friday, August 20, 2021 at 5:51:17 PM UTC-4 Dekatron42 wrote: >>> >>>> There is a nice article in NutsVolts magazine: >>>> http://www.nutsvolts.com/media-files/Forum-Articles/QA_201110.pdf >>>> where a powerful driver is shown, needs a small transformer but seems to >>>> be >>>> well designed with equations for calculations of the transformer. >>>> >>>> /Martin >>>> >>>> On Friday, 20 August 2021 at 21:37:46 UTC+2 Hannah Mishin wrote: >>>> >>>>> Theres a section on filament driving in my blog here: >>>>> >>>>> https://hannahmishin.com/blog/2017/4/30/russian-tri-color-vfd-indicator-clock >>>>> >>>>> *Hannah Mishin* >>>>> * She/her/hers* >>>>> <http://hannahmishin.com/> >>>>> >>>>> *hannahmishin.com* <http://hannahmishin.com/> >>>>> >>>>> >>>>> >>>>> On Fri, Aug 20, 2021 at 1:48 PM Toby Thain <to...@telegraphics.com.au> >>>>> wrote: >>>>> >>>>>> On 2021-08-20 12:58 p.m., Paul Andrews 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. ... >>>>>> > >>>>>> >>>>>> FWIW I've used LM2575 1A adjustable step down for DC filament voltages >>>>>> in that range. >>>>>> >>>>>> --Toby >>>>>> >>>>>> >>>>>> > ... >>>>>> > >>>>>> > 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 neonixie-l+...@googlegroups.com >>>>>> > <mailto:neonixie-l+...@googlegroups.com>. >>>>>> > 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 neonixie-l+...@googlegroups.com. >>>>>> To view this discussion on the web, visit >>>>>> https://groups.google.com/d/msgid/neonixie-l/ce44816f-120e-abae-060f-fe062d24f836%40telegraphics.com.au >>>>>> . >>>>>> >>>>> -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. 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