naked nixie - modern take on nixie clocks

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1 year 8 months ago #7577 by vladco
Hi,

I wanted to share with you my not yet finished nixie clock.



The story:
I first saw a nixie tube clock some years ago and I said I need to have one. Time has passed and it was time to actually start building it and i set some project goals:
  1. front viewing tubes
  2. hardware (cathode drivers) made with jelly beans parts (like Dave from EEVblog like to call them) - this was mostly because prices at the distributors in Romania are high and the availability of some high voltage drivers usually used in projects are simply not available, also it needed to be modular because i haven't decided yet if i want a 4/6 tube clock
  3. it needed to have WiFi simply because i had most of the software written for a different clock which has an web interface.
  4. power in should be 5V so i can power it from a phone charger
  5. nice hardwood case

After i had the goals set i started looking for tubes and i chose the IN-4 because they had a nice size (not to small and not to big) and i found them on ebay sold by someone from Romania so i could source them locally. In the process of searching for tubes i found a nice IN-4 with a find grid from Ukraine, and between the bought tubes i found one that has slightly different digits

For hardware (cathode drivers) i found this blog post threeneurons.wordpress.com/nixie-power-supply/ which talked about using low voltage drivers with zener clamping and i thought i would give that a try. Driving the cathode drivers was accomplished with the good old '595 shift register. At that moment i have decided i would go with direct drive instead of multiplexing.

Initial HV power supply was based on M. Moorrees MK 1.5 design which worked perfectly for testing but had the minimum input voltage too high for my goals.
After spending a lot of time looking for a design which will allow a smaller input voltage i found Taylor HVPS which were a perfect fit.

Fast forward some 1-2 months for PCB development and production and the first prototype was working, though i have chose to use the ULN2003 with a 47V clamp which for my IN4 was too low and caused a "glow" when no digit was driven, but moving to higher voltage SN75468 with 75V clamp voltage solved the problem.

As for the brains i went with the ESP8266 because i had most of the software already written for a different WiFi clock. While waiting for the brains i designed a nice wooden case in Fusion360 and with some help from NOD makespace the case came to life (oak wood, CNC milled)


anyway i was a nice journey and the clock is almost complete, some small firmware changes are needed and the case still needs to be finished :)

some pictures/videos with various stages of the build process goo.gl/photos/xAqDbSyT5gKFA5jb8

Vlad
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1 year 8 months ago #7578 by Ty_Eeberfest
Looks good!! How well does the ESP8266 maintain accurate time, e.g. how often do you need it to update from NTP (or whatever) to stay within +/- 1 second of correct time??

Look into it later when the dust is clearing off the crater.

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1 year 8 months ago #7579 by vladco
Hi Ty,

The main clock routine is implemented in a system timer of the ESP and I do an update every 12hours from NTP, not sure how accurate it is because I never looked into it, so far it was good enough :D

I will however look into implementing a better NTP (actually SNTP) client taking into account all the delays added by the communication and so on.

Regards
Vlad
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1 year 8 months ago #7580 by Ian
Hi Vlad,

really nice work! I'm curious about a few things:

Did you have to use any level shifting on the outputs of the ESP8266?

Do you do anything for DST? Do you have an algorithm for that, or are the dates sort of "hard coded"?

Does the clock do any dimming? I am facing a problem doing dimming on the ESP, because the human eye is very sensitive to changes in brightness, and when the ESP works on web, it stops working on the dimming (it is single core, web gets priority). I'm using dimming using PWM of the HV, and the PWM signal needs to be really stable.

Which ESP are you using ESP12? Did you have a look at ESP32? (My next design is probably going to be based on ESP32).

Would you like to do an article about your experiences? I'd help you with putting it on the site if you were interested... I'm sure the readers of the site would love to read about it...

Ian

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1 year 8 months ago #7582 by vladco
Hi Ian, thanks, a lot of work went into it.

to answer your questions:

1. the ESP is driving the '595 shift register which is a TTL part, even if i power it @5V the 3V3 from the ESP is enough to register a logic one, so no level shifting, i could also power the shift register from 3V3 because the variant i am using could got down to 2V VCC

2. DST currently is handled manually via webui but the plan is to move to an API provided by google developers.google.com/maps/documentation/timezone/intro which should give you the timezone and DST based on geographical location but i haven't looked into that yet manually works just fine atm :)

3. they idea was it should do that, and i was going to use the OE (output enable) of the '595 shit register for that purpose - unfortunately i didn't pay close attention to the datasheets where its stated that when the OE is HIGH the outputs are HiZ and i am not entirely sure what the darlington array is doing when its not driven.

for the webui I'm using the great work of Hristo Gochkov, with his implementation of AsyncTCP, AsyncWebServer which compared to the stock tcp/webserver implementation is a x10 (maybe more) improvement in speed, resources and usability. github.com/me-no-dev/ESPAsyncWebServer , github.com/me-no-dev/ESPAsyncTCP if you are not using this and you are serious about using the ESP for webui and other task take a look at them - you will not regret it :D

4. The ESP is the ESP07, i haven't looked yet at ESP32 because currently the resources i have on the ESP07 are enough for what i am doing.

regarding the article, sure we can talk about that :)

Vlad
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1 year 8 months ago #7583 by vladco
Regarding your brightness issues you may want to look into brightness correction or gamma correction as is sometimes called

A few years ago I did a project with some LEDs and I achieved linear brightness using a lookup table to drive de PWM, you can find the lookup table here github.com/putyn/theFlower/blob/master/s...theFlower/soft_pwm.h with a link to the original source

I am not sure if Nixie respond the same as LEDs but you could give it a try.

Also if anyone is interested I have a github repo with all the work done for the clock github.com/putyn/nixie-clock - it's still a work in progress :D

Vlad
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