nixie clock - Page 1
Forum section: electronics / projects

author: Boschi
author_rank: Regular Contributor
timestamp: July 14, 2020, 10:40:44 pm
content: so, as every good electronic hobbyst, for me has come the day to create my own nixie clock.i found this very helpful post and corrected some errors thanks tohimi want to keep it as cheap as possible, and i want to implement by myself the HV power supply. i based mine offthis design.i have already lying around some IN-1 nixie,here the specs!keep in mind that everything will be ordered through lcsc, so if there are things that could work on the "original" ic but are sketchy on the clones let me know.i want it to be able to work whitout power for a few months, updating the time but whitout visualizing it. it will be powered by a 18650 cell and it will have an external BMS (this explain the 4056 on the main schematic).in order to do so there are a few diodes that avoid backfeeding the battery when there is power , and avoid backfeeding the regulator (an AMS1117 5V) when there is not. at that voltage it should have something like 5uA of reverse current, could it be a problem for the battery in the long run?is the rc network on the reset pin of the second 4017 in the minutes section really necessary? again, because i'll use chinese clones instead of originalsi am not sure about the rc network in the top left corner of the hour and minutes section. the logic is that the pulse of H IN and Min IN are easily able to drive the clock in of the IC because the other 1uf cap is left floating, but the impulse of the 1Hz in need more capacitance in order to overcome the 100nf capacitance of the hours or minutes pin.the NPN transistors are MMBTA44this is the oscillator. about this i have a doubt. im not able to understand if its the 3.3V version or the 5V one. should i just slap a 3.3V regulator to drive it?everything will be mounted on a 15*10cm board (or there about) with 6 screw holes and standoff that keep it raised from the base below.thanks!

author: profdc9
author_rank: Frequent Contributor
timestamp: July 14, 2020, 11:00:47 pm
content: If you want it to run for months without power, I think you are much better off with a DS3231 module. They are about $3, but can often be found for much less, are very accurate and temperature compensated, and can run off of a coin cell for many months. I think you will have a hard time getting the discrete CMOS circuit to have as low of a power consumption.Of course, they are I2C addressed, so you probably need some kind of microcontroller to read and update the time. I used an Arduino Nano because the cost wasn't such a concern for me (buildability as a kit was) but a STM32F0 is less than a dollar and super powerful for you what you want to do.I implemented a similar refresh system, except I just used 74HC595s and directly addressed the cathodes with shift registers. You can see my project athttp://www.github.com/profdc9/NixieClock/

author: Pawelr98
author_rank: Regular Contributor
timestamp: July 14, 2020, 11:49:51 pm
content: Few notes:Why use the MC34063 which was never really meant for driving mosfet loads ?Use UC3843 which will provide better efficiency as well as a dedicated mosfet driver.Try to driveallthe digits from time to time.Read about cathode poisoning and why lighting up all digits at least once in a while stops the poisoning.My clock kit uses "slot machine" every hour. Basically it goes through all the digits at new hour.Therefore there should be a driver for all the digits in a tube.As an alternative you may just swap the tubes around once in a while.Generally speaking MCU does a better job as implementing many advanced features is easy.This includes tube multiplexing.Only one cathode driver is needed for as many tubes as you need.What is needed is anode driver which is basically NPN+PNP combo per single tube.Less elements equals lower power draw.

author: Boschi
author_rank: Regular Contributor
timestamp: July 15, 2020, 12:23:21 pm
content: honestly i want to keep it discrete, without using an MCU, i see it as having more "personality". besides, nowadays its just a piece of "art" if you will, by having a phone in your pocket it loses all practical meaning.the UC3843 its better than the MC34063, you are right, it will reduce a bit the BOMi didnt think about cathode poisoning.but is it really a problem? i mean, i want something simple and functional whitout any other feature, so other than displaing the time it wont do anything else. i dont need the other digits to work, so unless there are longevity problems i doesnt matter. so, are there any longevity problems? also, what is best practise about nixie current? a lower current will keep them active longer or a higher one is better?

author: NivagSwerdna
author_rank: Super Contributor
timestamp: July 15, 2020, 01:53:27 pm
content: Quote from: Pawelr98 on July 14, 2020, 11:49:51 pm^ thisA clock that says the wrong time is rubbish... use a RTC but back it up with regular NTP SyncHave occasional patterns to avoid cathode poisoningHave off times to save tube lifeConsider dimming... with ambient light or at other timesImplement nice effects like scroll in/out date, roll back on carry over

author: robca
author_rank: Frequent Contributor
timestamp: July 18, 2020, 12:28:28 am
content: I know you said no MCU, but if you change your mind, I would highly recommend an ESP32 or ESP8266, so that you can easily do NTP time sync. There are libraries for the ESP to put it in AP mode when no know WiFi is recognized, and self configure on any WiFi network that wayUnless you plan to expose the insides, nobody will know what chips you have used, anyway. And using a modern RTC in a "traditional clock circuit" would in any case violate the designAnd, yes, cathode poisoning is a real problem with nixie clocks and easy to fix. Don't skimp on that, or your nixies will have a much shorter (and paler) life. Plenty of examples of how to avoid it (most using an MCU because, well, it's easier that way)

author: Boschi
author_rank: Regular Contributor
timestamp: July 24, 2020, 09:21:39 pm
content: well, at the end all of you changed my mind, im using an arduino and a RTC to keep the time (plus a bunch of 595).at this point i have to ask, what is the best way to drive them? i have already some IN1, so they are not long life.should i pwm them? should i use a low frequency (like 100hz) or a higher one? what should be the on current? nominal is 2.5 ma, to extend life what is better, around 2ma?i dont think to switch them off at a regular time, because i dont want to integrate a pir and this is a gift to my brother wich is a cook and doesnt have very regual hours, but i want to add a ldr in order to dimm the nixie when there is not much light around.to avoid cathode poisoning, its enough to count each digit (0 to 9 repeating) for a minute (so a total of 6 second for each digit)?sorry for the silly questions but honestly im trying to read everything and there are quite a few contradictory answers about.about the MCU, i dont want to connect it to a NTP server. mainly because for most of the time it wont be around a wifi, and i want to use a ds1302 coupled with a TCXO in order to get max 1 minute of error every year. togheter they should consume less than 10uA, it should last for about forever on a 18650 lipo cell.PS: sorry for the late reply, im a uni student and i have a few exams to study for. dont expect updates for a while!

author: tooki
author_rank: Super Contributor
timestamp: July 24, 2020, 09:32:29 pm
content: Don’t bother with a DS130x. They’re just not accurate. Use the DS3231, as others already said. It’s got a built in TCXO. They’re so accurate that I can’t even remember the last time I had to adjust my clock based on it — it’s probably only every two or three years or so that i ever notice any deviation from my phone and adjust it.You can get the DS3231 from eBay or Ali as a breakout board or bare chip for $1-2, and as far as anyone knows, there are no counterfeits, as the construction method inside them is probably too complex for the counterfeiters.Also, there are many Arduino libraries for the DS3231, making them super easy to talk to.

author: Boschi
author_rank: Regular Contributor
timestamp: July 24, 2020, 10:37:44 pm
content: you are right, they are better. the main problem is that lcsc is out of them, but it has the PCF2129 wich is even better (3ppm vs 5ppm) so ill use that.also, im just using a few pins, im thinking about using a attiny 1616. 16kB of flash and 17 I/O. on lcsc is about 90 cents vs an atmega 328 wich is about 1.80€. i should use 9 pin (3x595, 2xbuttons, 1xldr, 1xpwm, 2xi2c for the pcf) so i have plenty for anything that ill add later on if i want to. with serial and the pcf library i have still more than 10KB free, so no problem even there.

author: tooki
author_rank: Super Contributor
timestamp: July 24, 2020, 11:21:56 pm
content: Actually the original DS3231, the DS3231SN, is 2ppm. The reduced cost MEMS version, the DS3231M, is the 5ppm part.I haven’t used the M version yet, but I now have one to try.

author: dimasua
author_rank: Newbie
timestamp: September 04, 2020, 12:34:10 pm
content: I bought several months ago from these guys a nixie clock based on Soviet nixie tubes:https://nixiedream.com/And of course I disassembled itThey use MC34063 and DS3231. So far all good, accuracy is around 10 sec/month

author: Pawelr98
author_rank: Regular Contributor
timestamp: September 05, 2020, 02:58:41 am
content: Quote from: Boschi on July 24, 2020, 09:21:39 pmSorry for late reply.IN-1 can work well below 1mA IIRC.I used those tubes for an university project.For driver either get soviet K155ID1 or 74141.Soviet version is more reliable (can withstand higher off voltage) I heard.Otherwise use ULN2003 with a protection zener (through the freewheeling diode pin) to avoid breakdown.Then a BCD->decimal decoder for driving the ULN2003.7546 is just the same but can withstand 100V so clamping isn't as important.A discrete solution that can withstand some serious abuse is just discrete MPSA42 (or the SMD mmbta42 variant) 300V NPN transistors.Connect those with a decoder just like ULN2003.I used those to control nixies that were driven directly from 230V mains.300+V at anode and 200+V on cathodes.For driving pattern I would say just multiplex them like any display.Most of those tubes can last for years of use without any problems.In my university there's gear from 70's and 80's that still works fine with original tubes.No need to PWM them really unless you want to run continously with 4 individual drivers.Multiplexing is PWM in it's own way. By adjusting the timing of the multiplexing you basically get adjustable PWM.Just set the timing for no ghosting and limit the current to minimum clearly visible.Lower current makes it slightly dimmer but it increases life.As for cathode poisoning.Unless you want to do it in a middle of a night then make it faster.Better divide it into smaller periods that are more frequent.Half a second for each digit and do it every hour or so.

author: xavier60
author_rank: Super Contributor
timestamp: September 05, 2020, 08:57:51 am
content: If using discrete BJTs, there is no need to use a whole bunch of Base resistors.

author: Boschi
author_rank: Regular Contributor
timestamp: November 29, 2020, 11:42:05 am
content: here we are! almost finished! (i have attached a photo of the final result)the software is almost perfect, just a few bugs to resolve and its ready.right now ithe tubes are running at about 1.5ma, i'll increase the resistance to drop even more the current, there is also a pwm regolation in order to change the brightness.there is a thing that is unclear to me, why is it running slow?im using a pcf2129AT, specified at +- 3ppm between -15 to +60 °C, wich should be something like 95 seconds a year max but compared to my pc (NTP syncronized) it seems that in 4-5 days has lost 15 seconds already.i poll the RTC very frequently, pheraps it somehow slow down the time? other than that im not really sure what could be, the power is 4.2 volt when on and 3v when just timekeeping, it always stayed at around 18 -23 °C (my room, and i am always here thanks to remote learning). im baffled, and also thanks to the library that im using i cant even adjust the ppm correction factor inside the RTC.

author: B0B45
author_rank: Contributor
timestamp: December 01, 2020, 04:05:33 am
content: Hey,I made a tiny nixie clock for a costume early this year based on an LT3757 as Flyback with a Wuerth 1:10 transformer. For the tubes i used the HV5530 300V shift register.The Plan for the supply can be found in the datasheet.-B0B