@gregebert Thank you for the anode current limit suggestion. However, I have already produced the board so I might try it out in some future prototype. I have, however, scaled the current in each cathode down so that the sum of them all (when all segments light up) will not exceed the maximum current per tube. I do realize this will probably mean that the tube will have somewhat dimmer appearance, but hopefully not too much. I'll post results once I get to soldering the parts and trying it out!
@Nick Your site is a very valuable resource, this is my second clock using the HV power supply based on your design, the last one is now some two years in operation and works very well. On Wednesday, January 16, 2019 at 4:29:23 PM UTC+1, Luka C wrote: > > Greetings everyone, > > It's been a long time since I posted here last time and I've completed my > modular clock design since then (photo attached). The main idea is to have > a compact smart single "control board" which you can then add different > number of daisy chained "display boards" for various tubes. Now, for the HV > power supply, I've used a MAX1771 design presented here: > https://desmith.net/NMdS/Electronics/NixiePSU.html . Tested it with 6x > IN-18 tubes and it drives them at 5mA per tube fine. Now, I'd like to > modify the power supply (without changing the board layout, considering all > components are SMD) so that it can power 6x B7971 tubes (at ~17mA per tube > with all segments lit is what I have in plan). The link with the power > supply description contains a paragraph on how to expand the design so that > it can handle such currents. The thing is that since the website was > published, the FET proposed there is no longer in production and the > inductor is not compatible with the SMD layout (the once that author > proposes for higher current is a bobbin type). > > After doing a little digging on replacement components, I've come up with: > > 1. Replacement FET candidate: *FQP22N30 > (http://www.mouser.com/ds/2/149/FQP22N30-1009534.pdf > <http://www.mouser.com/ds/2/149/FQP22N30-1009534.pdf>) , *the difference > being that this FET has a maximum drain current of 21A, while the > discontinued one the author suggests has 32A. > 2. Replacement inductor candidate: *SRP1265A-470M* > (*https://www.digikey.com/product-detail/en/bourns-inc/SRP1265A-470M/SRP1265A-470MCT-ND/4876720 > > <https://www.digikey.com/product-detail/en/bourns-inc/SRP1265A-470M/SRP1265A-470MCT-ND/4876720>*) > > , *Irms = 6.5A, Isat = 9.5A , *original one suggested by the author has > Idc(max) = 8.5A. The new replacement candidate has a max DC resistance of > 90mΩ, while the original one has 20mΩ (this would decrease efficiency > somewhat, but there doesn't seem to be any footprint-compatibile inductor > with lower DC resistance?). > 3. Rsense *0.025Ω 2010 rated at 1W*. > > Do you think this would work? > > Thanks in advance and best regards, > Luka > > [image: IMG_20190116_154939.jpg] > > > > -- 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/46821861-adb6-47d3-989a-2d75c4714436%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
