Speaking of power supplies, I've been running a few experiments using HVAC 24VAC transformers. I choice this type of device, since almost all Radio Shack stores have closed, since 2015. I still have one near me, in Tehachapi, CA (a franchise). Also, in recent months, the Fry's chain is clearly in trouble. They have empty shelves, and will most likely close just after the new year. But HVAC supply stores are relatively common, and they all carry 24VAC transformers, that are used to relay thermostat data (simple switch closer) back to the heating & AC system. They currently sell in the $12 ballpark.
To get 170V+, from these transformers, doesn't even involve a switching suppy. I got some numbers off a simple multiplier circuit: <https://threeneurons.files.wordpress.com/2019/11/hv24_mult_s.jpg> With the capacitors used, and a 40VA transformer, this thing can deliver upto 70mA, before the output drops below 170V. Note, that's the average voltage, shown on a meter. Any peak in the ripple, exceeding 170V, will strike a nixie tube. As a baseline, I hooked up one of my switching supplies. It was modified so that the coil got the full DC rectified & filtered voltage (~36V), but the control circuit was limited to 12V, as not to destroy the power FET. Also the coil value and timin cap value were altered. Though the coil, was still a small drum coil, of the same series. <https://threeneurons.files.wordpress.com/2019/11/hv24_sch_s.jpg> I surprisingly got 100mA output, with the supply only getting comfortably warm. Using fullwave rectification, smaller 20VA & 30VA transformers can be used. Note: I got 20W (120mA) out with the 20VA transformer. NO IT WAS NOT 100% EFFICIENT ! The 20VA transformer was just putting out more power than its rating. So, this kind of load, should only be presented intermittently, else that transformer will eventually fail. Of course to make this usable, +5V, or some other low voltage needs to be drawn from the same transformer. If less than 50mA is needed, a 680 ohm 2W resistor, and 4.7V (1W) zener, should do the trick. For higher currents, a switching buck converter can be used. The MC34063 can handle up to 40V, and should safely deliver a few hundred mAs. -- 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 [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/2821ba92-2b8c-4242-8fc5-499552fa5407%40googlegroups.com.
