I wanted to share with you my not yet finished nixie clock.
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:
front viewing tubes
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
it needed to have WiFi simply because i had most of the software written for a different clock which has an web interface.
power in should be 5V so i can power it from a phone charger
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
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
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...
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
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.
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
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