The tubes are direct drive but the issue is that the tubes which display only a dash (instead of a colon) are cycling on and off every second, so the LEDs would be constantly turning on and off. It is only when one segment or DP is energized that the dark turn-on is an issue, so it would be too noticible to be doing that with the LEDs. We did try to send millisecond hits to all of the tube segments on each illumination of the dashes. The thinking was that if it was brief, it might not be noticible. In practice, the other segments had to be powered long enough to actually ionize the gas and they do not turn on and off fast enough to avoid a very visible (and annoying) flash.
On Tuesday, February 20, 2024 at 12:14:50 AM UTC-6 gregebert wrote: > No problem; amazing what you can do with 500nm..... > > Since they actually are UV LEDs, you may want to tweak the software so > they can be turned off after a few seconds if your clock is direct-drive. > If it's multiplexed, you probably need the UV on continuously in the dark > (would be very informative to run an experiment here to find out....). > > > On Monday, February 19, 2024 at 9:53:17 PM UTC-8 Jeff Walton wrote: > >> Hi Greg, >> >> The LEDs were 385nM, not 885nM. >> >> Clearly the LEDs were UV. I initially thought the 365nM would be more >> effective but they were not. The 365nM parts might have also been less >> desirable from a safety standpoint and were also quite a bit more >> expensive. The 405nM UV LEDs are less expensive and more plentiful but >> seem to have more visible light spill. >> >> I wish that I could edit the original post, but no such luck! >> >> Jeff >> >> -------- Original message -------- >> From: gregebert <[email protected]> >> Date: 2/19/24 10:56 PM (GMT-06:00) >> To: neonixie-l <[email protected]> >> Subject: Re: [neonixie-l] Helping Nixie Tubes Fire in a Darkened Room >> >> 885-890nm ? That's infrared. If the LEDs are always-on, then I'm glad >> you're using IR instead of UV because it's much less harmful (perhaps >> harmless ?) to materials and humans/pets, etc. >> >> BTW, those are really interesting tubes. I dont think I've ever seen >> tubes with a solid/opaque anode. >> >> On Monday, February 19, 2024 at 5:19:12 PM UTC-8 Jeff Walton wrote: >> >>> I posted this a couple months ago regarding the MG-17G display tubes >>> that wouldn’t fire reliably in the dark. The final resolution for it was >>> to mount some 885-890nM UV LED’s under the tubes. A completely updated >>> display board with LEDs driven from a fixed supply and a transistor on an >>> LDR so that they LEDs only turn on in a darkened room. This 885nM >>> wavelength seemed to work better than the 865mM and was less visible than >>> the 905nM LEDs. I wasn’t trying for a visible underlighting effect on the >>> tubes, so they are being driven at about 2mA so that there is sufficient >>> light without excessive glow. >>> >>> >>> >>> The clock is a Richard Scales design and this is the only one (so far) >>> with the “keep alive” LEDs. The tubes do not have a keep alive cathode, so >>> this method works. Otherwise, any single segment or decimal point would >>> not fire reliably. Now the tubes light dependably. Thanks to Richard for >>> the new board and a lot of back and forth to get this working right! >>> >>> >>> >>> The original PCB: >>> >>> >>> >>> The new PCB: >>> >>> >>> >>> The display in operation: >>> >>> >>> >>> The case in Place with LEDs on: >>> >>> >>> >>> The finished clock: >>> >>> >>> >>> Once we got past the issues with dark operation, the clock performs very >>> well! >>> >>> >>> >>> Regards, >>> >>> >>> >>> >>> >>> >>> >>> *Jeff Walton * >>> *------------------------------* >>> >>> >>> [email protected] >>> [email protected] >>> (952) 943-2064 Home >>> (612) 865-5560 Cell >>> >>> >>> >>> *From:* [email protected] <[email protected]> *On >>> Behalf Of *Jeff Walton >>> *Sent:* Wednesday, November 29, 2023 8:44 PM >>> *To:* neonixie-l <[email protected]> >>> *Subject:* [neonixie-l] Helping Nixie Tubes Fire in a Darkened Room >>> >>> >>> >>> I've recently come across a situation where I have some tubes in a clock >>> that are being directly driven and are having trouble starting when the >>> room is darkened but light right up when a room light is turned on. These >>> particular tubes were probably intended for use in a calculator. They are >>> seven segment neon MG-17G tubes. Once the tubes have any of the segments >>> lit, there is really no issue with the performance. It's when the tubes go >>> completely dark if a space is used while scrolling a message or lighting a >>> dash on and off to emulate a colon. I'm wondering if others have found any >>> particular tricks to help convince tubes to light up. There is no >>> "baselighting" and the HV is ~172v. I'm considering increasing the HV by >>> 10-15v but don't want to over drive the tubes. Short of putting a >>> radioactive source in the vicinity, are there other things that anyone has >>> had any luck with? >>> >>> >>> >>> Jeff >>> >>> -- >>> >>> 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/d5713f02-ec1d-493d-b12f-644fb080ee71n%40googlegroups.com >>> >>> <https://groups.google.com/d/msgid/neonixie-l/d5713f02-ec1d-493d-b12f-644fb080ee71n%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 [email protected]. >> To view this discussion on the web, visit >> https://groups.google.com/d/msgid/neonixie-l/bb3b4ba6-8597-48c9-af56-c0a9e3de97c7n%40googlegroups.com >> >> <https://groups.google.com/d/msgid/neonixie-l/bb3b4ba6-8597-48c9-af56-c0a9e3de97c7n%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 [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/2f40a28b-cc81-4278-b37f-3ae032f4eae8n%40googlegroups.com.
