Transformer
Did some digging around with Digikey and LTSpice. Seems like my efficiency goes up if I use a lower ratio transformer but all I could find in "current transformers" was as low as 1:20 and 1:40. I got the 1:40 for now but plan on going down to 1:20 for the final build. The inductance of the primary seems to have a sweet spot as well, something like 33uH is too little while the 4.5mH I had before is too much. I also noticed that the polarity of the secondary coils really matters. I was thinking its just a sine wave going out so it doesn't matter which leg of the secondary I connect ground. Seems like that's false with both empirical and simulation resulting in a more efficient transfer if I have the polarities antiparallel, can't quite understand why but whatever.
Did some digging around with Digikey and LTSpice. Seems like my efficiency goes up if I use a lower ratio transformer but all I could find in "current transformers" was as low as 1:20 and 1:40. I got the 1:40 for now but plan on going down to 1:20 for the final build. The inductance of the primary seems to have a sweet spot as well, something like 33uH is too little while the 4.5mH I had before is too much. I also noticed that the polarity of the secondary coils really matters. I was thinking its just a sine wave going out so it doesn't matter which leg of the secondary I connect ground. Seems like that's false with both empirical and simulation resulting in a more efficient transfer if I have the polarities antiparallel, can't quite understand why but whatever.
Tubes on Tubes on Tubes
Got new tubes in. Picked NL-5870ST's from eBay. There is a german made one that's 1.5mm thinner but its damn near impossible to get whereas the 5870 is abundant. Got em in a 5 pack for $50 total, not bad. They come with a spacer you can throw away which makes them ~30mm nipple to base and 13mm wide. I'm also heavily considering just soldering directly to the board to save on space. Also tried the neon lamp for the "one" digit, turns out it sucks as a stand in for it. The filament is super short compared to the 13mm tall digits the 5870 has and it looks cheap. Moving forward with 4 digits!
Got new tubes in. Picked NL-5870ST's from eBay. There is a german made one that's 1.5mm thinner but its damn near impossible to get whereas the 5870 is abundant. Got em in a 5 pack for $50 total, not bad. They come with a spacer you can throw away which makes them ~30mm nipple to base and 13mm wide. I'm also heavily considering just soldering directly to the board to save on space. Also tried the neon lamp for the "one" digit, turns out it sucks as a stand in for it. The filament is super short compared to the 13mm tall digits the 5870 has and it looks cheap. Moving forward with 4 digits!
Switches and Arduino
Pushing my luck, I decided to order some of the tiny switches I picked out. Hooked it all up to an arduino I found around the lab and wrote code to turn digits and tubes on. At first I too low of a resistor on the gates of each digit which pushed too much current through their emitter and across the 150R which messes with the regulator's feedback. Went to 33k and it's back to normal. See the schematic below for calculations on how to pick the mosfet resistor values for each tube.
Pushing my luck, I decided to order some of the tiny switches I picked out. Hooked it all up to an arduino I found around the lab and wrote code to turn digits and tubes on. At first I too low of a resistor on the gates of each digit which pushed too much current through their emitter and across the 150R which messes with the regulator's feedback. Went to 33k and it's back to normal. See the schematic below for calculations on how to pick the mosfet resistor values for each tube.
I'm getting weird ghosting happening when one tube is off since i'm muxing/busing the numbers. But man are they pretty!!! You can see one of them I tried fading the numbers by raising the ratio of off-time to on-time.
Next Steps:
Now that I've got some experience with the tubes I'm gonna work on the case a bit more and maybe even 3D print one to see how it'll look.
Now that I've got some experience with the tubes I'm gonna work on the case a bit more and maybe even 3D print one to see how it'll look.