David and all, Just a quick update. I finally had some time to remove all cables and to solder everything directly, with the nixies being on sockets and I'm pleased to report that it all works great!
Re: accelerometer ADXL335. I cannot get to solder that chip properly, quite tricky even under the microscope. I'll start again but I'm not too concerned about it, maybe I'll replace it with a chip in a different package, I find the LFCSP_LQ too tricky to hand solder even when following the recommended soldering profile. Re: HV 1308B - Turns out that the PCB layout that I posted here - while not ideal - works ok (ok-ish?) or at least it's not a disaster. I've added some tiny LEDs along the anode lines and they work great but they want a 1k resistor in series otherwise the tubes glow a bit blue, so I need to work around that. Next I'll look to add a photodiode to control brightness through PWM I suppose, the intention being to save power more than to dim the tubes. But I have some PIC assembly to chew first for PWM and perhaps I'll add touch buttons too... Nothing new for this group, but a whole new world for me. Feeling like I've been missing out! Thanks again for the suggestions given, Max Il giorno lunedì 31 agosto 2020 alle 20:11:55 UTC+1 Max DN ha scritto: > Now this is an honour! David Forbes himself! I'm a big fan. > > David, thanks for taking the time to reply in detail. I have been studying > your circuit for 2-3 months now (I know, for most people here it may take a > day or so, but my knowledge of electronics is very basic however it's > always been a passion of mine). My day job is in a totally different field > (banking) and since Covid lockdown started in the UK I have dedicated some > of my spare time to this project, just as a way to switch off, so to speak > :-) > > My wife insists I should just buy your watch but I like a good challenge > (more so I'd like to try to make a HVPS at least as efficient as the > Kopriso but that's some time away for my basic knowledge). I may still get > your Cathode Corner watch as a courtesy for sharing your entire firmware > and schematics. Beside, I like it as well and perhaps start from there and > try to update the software to add functionalities (such as date etc). I'd > also like to improve the efficiency of the high voltage circuit and have > worked on 2-3 projects in parallel, but I'm leaving those in standby for > now given my limited spare time. > > I do think my issues are the amount of cables currently running to the > Nixies as well as poor layout. And perhaps many more. In fact, I'm still > surprised that it works at all, although not perfect (the accelerometer is > not working at all or not working well, I'll look into that later, probably > due to poor manual soldering skills there). > > I have noticed that if I even try to just measure the voltage on the > feedback pin (I only get 1.17V or so) the brightness of the Nixies changes. > > The multiplexing doesn't work well with my current set up and you can > clearly tell it's there. I have taken a video if you are curious at all. > I'm loving this project and would like to keep the watch size of > 38mmx38mmx16.5mm which I think is achievable. > > Needless to say, David, your PC board design is compact and neat, my first > mistake was to have the feedback line running across the entire board as > well as the switching pin so far from the transformer and with its copper > wire running under the 1308B! Oops. > > Last, it's a puzzle for me that a (random) 2.2k resistor in series with > the VCLAMP line seems to improve stability. And works better with 3.2k. > It's probably affecting the resistive divider somehow. > > I think you are spot on with all of your suggestions (of course). I'll > focus on the feedback line for now and perhaps just start from scratch soon > by redesigning the high voltage layout. > > Thanks so much again. > > Massimo > Il giorno lunedì 31 agosto 2020 alle 19:13:26 UTC+1 nixiebunny ha scritto: > >> Massimo, >> >> Hi. I see that you are trying to make the Cathode Corner Nixie watch >> circuit work, using your own circuit board design. it's not an easy >> circuit to build, because the design was optimized for size and >> efficiency, given the parts I had available. >> >> The power supply is designed to make 180V with no load. It is designed >> to make about 10mA of current with one Nixie tube lit, where the Nixie >> tube regulates the voltage to about 150V. There is a third voltage >> level that is selected by the TiltP signal, which reduces the HV to >> about 90V by changing the feedback divider current, through that 33K >> resistor. This is done to provide blanking for the tubes while the >> power supply is active, which makes the multiplexing cleaner. >> >> You can see that all of these parts interact, and the feedback >> resistor values were tuned after building a few watches, to get the >> display to look the best. I wouldn't have made it this way if I was >> only building one watch! >> >> The clamp voltage is not critical, since the clamp Zener diode is only >> conducting when high voltage is on yet no tube cathode is enabled. >> >> The circuit board layout is critical. I do not think that it will work >> properly if you have any length of cable on the Nixie tubes. This is >> because the capacitance of that cable, combined with the high votlage >> switching of mutliplexing, will generate noise and affect the timing >> of the cathode turn-on and turn-off. >> >> Here's a picture of the PC board design for the round watch power >> supply. You can see that I made all the high current 3V power and >> ground traces very short and wide, to prevent problems with the >> switching currents radiating into the feedback circuit. In fact, my >> first prototype PC board had the feedback line running across the >> power supply, and it failed, so I had to add a wire to move that >> sensitive line away from the noisy switching circuit. >> >> I hope that this description helps you to understand where to focus >> your attentions. >> >> >> On 8/31/20, Massimo Di Noi <[email protected]> wrote: >> > Hi all, >> > >> > I'm been following this group for a while and finally decided to go >> back to >> > >> > a hoppy that I had 15-20yrs ago or so, to brush up my old knowledge and >> to >> > build my personal nixie watch starting from what David at Cathode >> Corner >> > kindly shared, but looking to improve its efficiency with new chips and >> to >> > add functionalities similarly to Kopriso watch or else. I like the >> > capacitive buttons etc. >> > >> > -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. 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