*Martin* - Do you know how long dekatrons last ? I have an A-101 running as a spinner in one of my clocks, and it's been going 60RPM 24/7 for almost 8 years with no signs of degradation. I use 30k dropping resistors at the cathodes, and the current is right at the spec value of 450uA, so that gives about 15V for "steering", and the driving waveform is 3-phase with overlap. I
On Tuesday, February 16, 2021 at 4:15:05 AM UTC-8 Dekatron42 wrote: > There is one more dimension to think about when running a dekatron and > that is that over time it will degrade due to sputtering affecting the > electrodes and to maintain a correct counting when it ages you should keep > the voltages as described in the datasheet, especially the guide and bias > voltages as those are needed when the dekatron nears its end of life - it > is the same effect that is in play if you want to raise a dekatron from the > dead if it has been heavily used or just stored for a very long time > without use, raise the bias/pulse voltages and sometimes the anode voltage > to surpass the effects of the sputtering - effectively increasing the > current flow between the anode and the guides/cathodes. > > So even if dekatrons work at other voltages you will see the effects of > lower/incorrect voltages when they near their end of life, this has been > described in older litterature where the internals of dekatrons has been > disected in detail - you might just need some 10V below the glowing cathode > to move the glow on a new dekatron but as it ages it will stop working at > that voltage. > > /Martin > > On Tuesday, 16 February 2021 at 00:53:36 UTC+1 bung...@gmail.com wrote: > >> Those values were left over from the 5v circuit. I was more concerned >> with the level shifting from the PIC at 0 to +5v. >> Peter >> >> On Mon, Feb 15, 2021 at 6:48 PM Jon <deka...@nomotron.com> wrote: >> >>> I'd had a similar thought about increasing the bias resistors - it's not >>> necessary to run so much current (5mA) through that part of the circuit. >>> >>> OK, so your proposed conditions are that the dekatron will see are 400V >>> anode to main cathodes; guides swinging from +25V to -25V with respect to >>> main cathodes. Tube current will be about 345uA. >>> I've replicated these on my dekatron tester using a nice NIB GS10C/S as >>> the test subject and can confirm that they do work - the tube stepped fine >>> up at speeds up to over 4kpps once I'd woken it up a bit. >>> >>> Caveats: >>> 1) I only tried one tube. >>> 2) My circuit is rather different to yours so although the static >>> voltages are the same, the pulse shapes are almost certainly different. And >>> we didn't even talk yet about pulse durations, so I've no idea what your >>> PIC is spitting out. But as long as you're not trying to cut things too >>> fine, there's lots of latitude to find patterns that work. Keep things >>> north of 100us per phase and you'll be fine unless you've got a really >>> reluctant tube. >>> 3) I was running at slightly lower current (300uA) so you've probably >>> got a bit more margin for speed than I had. Recommended operating >>> conditions are 325uA +/- 20%, so we're both inside that range. But a little >>> more rather than less current is useful when pushing higher speeds. I'm >>> guessing though that you're looking for a much slower stepping speed for >>> this application though. >>> >>> If you've not already done so, I'd definitely second Martin's >>> recommendation to take a look at Michael Moorrees' dekatron work (he looks >>> in here from time to time too). He used a couple of elegant design tricks >>> which simplify the interfacing of dekatrons to modern electronics / >>> microcontrollers - I've followed his approach in pretty much all the stuff >>> I've built and it works a treat. Not to say that other approaches aren't >>> equally useful too of course. >>> >>> Jon. >>> >>> On Monday, February 15, 2021 at 9:39:13 AM UTC Dekatron42 wrote: >>> >>>> I'd raise the resistance to at least some 100k for the two bias >>>> resistors R5 & R6 in your diagram above. >>>> >>>> I'd also use the correct bias voltage and just use an MPSA42 with its >>>> emitter to common ground for the driver to simplify the circuit as Ronald >>>> Dekker and Michael Moorrees with their dekatron circuits. >>>> >>>> Different dekatrons need different bias and pulse voltages on the guide >>>> electrodes to count properly so accomodating for those requiremenst will >>>> remove a lot of problems and keep down the fault finding time. >>>> >>>> /Martin >>>> On Monday, 15 February 2021 at 03:05:12 UTC+1 bung...@gmail.com wrote: >>>> >>>>> You are absolutely right. 5v was not high enough despite Ronald's and >>>>> my confirmation that it would work. >>>>> I am changing to +25v and -25v and will have an optocoupler with the >>>>> diode driven from the 5v PIC and the transistor at the bottom of the >>>>> resistor between the two power supplies. It keeps it simple. I have to >>>>> order the optocoupler because none of my old ones have higher than 30 v >>>>> rating. >>>>> I will have to think about the extra two power supplies. Maybe I can't >>>>> avoid them. It will be a few days until I get the parts. >>>>> Peter >>>>> [image: Dekatron Circuit.jpg] >>>>> >>>>> On Sun, Feb 14, 2021 at 3:18 PM Jon <deka...@nomotron.com> wrote: >>>>> >>>>>> Interesting approach - not seen it rigged up quite like that. Let us >>>>>> know how it goes! >>>>>> >>>>>> My immediate question is whether there's a big enough potential >>>>>> difference between an inactive guide and a main cathode to get a >>>>>> reliable >>>>>> transfer forward from a deactivating G2 to the 'next' main cathode >>>>>> rather >>>>>> than back to the adjacent recently used G1 - 5V is much lower than the >>>>>> datasheet guide bias. Might be OK at slow stepping speeds with long >>>>>> guide >>>>>> pulses. Also the leading edge of your guide pulses is going to be fairly >>>>>> slow as Q1/2 come out of saturation and the guides are passively pulled >>>>>> down to the 'active' voltage. Most guide drive circuits use a NPN >>>>>> pull-down >>>>>> to the active state which creates a sharp leading edge and then a slower >>>>>> return to the inactive state. >>>>>> >>>>>> Jon. >>>>>> >>>>>> On Sunday, February 14, 2021 at 7:06:28 PM UTC bung...@gmail.com >>>>>> wrote: >>>>>> >>>>>>> Having finished the Amperex 8453 display I started on my Dekatron. >>>>>>> Thanks to all for the suggestions. >>>>>>> I read up on Ronald Dekker's clock project >>>>>>> https://www.dos4ever.com/decatron/decatronweb.html >>>>>>> and decided against a direct drive from a 74141 because, even if it >>>>>>> was practical, it would not look as good as using all the pins. It >>>>>>> would >>>>>>> look like the 8453 I just finished except without the number mask. >>>>>>> A few quick experiments showed that a -24v power supply was needed >>>>>>> for the easiest implementation.. This is my design. I will let you know >>>>>>> if >>>>>>> it works. >>>>>>> >>>>>>> A PIC drives the circuit: it starts with Q3 off to force a start at >>>>>>> 1. A high on R3 or R4 is the same as the switches in Ron's test circuit >>>>>>> placing -24v on the guides. As my PIC sends the BCD for the other >>>>>>> displays >>>>>>> and clocks the E1T it will generate the sequence to advance or retard >>>>>>> this >>>>>>> Dekatron.. >>>>>>> [image: Dekatron Circuit.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+...@googlegroups.com. >>>>>> To view this discussion on the web, visit >>>>>> https://groups.google.com/d/msgid/neonixie-l/62979e37-ef21-46e1-9b7c-45a4c4080238n%40googlegroups.com >>>>>> >>>>>> <https://groups.google.com/d/msgid/neonixie-l/62979e37-ef21-46e1-9b7c-45a4c4080238n%40googlegroups.com?utm_medium=email&utm_source=footer> >>>>>> . >>>>>> >>>>> -- >>> >> You received this message because you are subscribed to a topic in the >>> Google Groups "neonixie-l" group. >>> To unsubscribe from this topic, visit >>> https://groups.google.com/d/topic/neonixie-l/dQn3tFBYfoc/unsubscribe. >>> To unsubscribe from this group and all its topics, send an email to >>> neonixie-l+...@googlegroups.com. >>> To view this discussion on the web, visit >>> https://groups.google.com/d/msgid/neonixie-l/75f258db-83ea-4df3-9d50-52dcaed1461en%40googlegroups.com >>> >>> <https://groups.google.com/d/msgid/neonixie-l/75f258db-83ea-4df3-9d50-52dcaed1461en%40googlegroups.com?utm_medium=email&utm_source=footer> >>> . >>> >> -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. 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