A simple nixie stand alone display - Page 1
Forum section: electronics / projects

author: ppTRN
author_rank: Regular Contributor
timestamp: June 01, 2025, 01:58:29 pm
content: Hi,I found myself a couple of nixies and I made this simple circuit that cycles all digits. It is powered by a 9V power supply.You can find gerbers, schematics, 3d file ready to print and some pictures attached. Unfortunately it seems like I cannot attach a video of the digits cyclingIt uses an NL848 but it works with every tube, just wire it accordingly.Hope you like it

author: Analog Kid
author_rank: Super Contributor
timestamp: June 01, 2025, 05:29:16 pm
content: Ugh. Meta-objection here: your schematic posting has 2 strikes against it:1. It's in a PDF which I have to download, rather than just an image in your post which is right there.2. It's one of those "everything in a separate box" type schematics where you have to mentally connect everything together.Other than that, I wish I could help you but unfortunately can't.

author: pqass
author_rank: Super Contributor
timestamp: June 01, 2025, 08:34:27 pm
content: Nice.I too like to separate parts of the schematic into blocks, but not so much that you lose the big picture.I would have consolidated further into just:(i) BOOSTpwm with POWER SUPPLY,(ii) DIGITclk with DIGIT SELECTION, and(iii) CATHODE SWITCHES with NIXIE CONNECTOR.Most important (for me) is the input-to-output flow should be from left to right, top to bottom.I have no issue with the schematic attachment being a link to poke at. It's better than a dozen images filling the screen. I'd rather read the message first and decide whether to poke a link or thumbnail later.Now regarding the schematic...1. It's interesting that your +HT isn't regulated. I've used a 555 with a resistor divider feedback to maintain 170V. Although, I was feeding a variable load; 4 multiplexed 15-segment nixies rather than lighting just one cathode at a time.2. It's also interesting that using a 9V supply is enough to switch the IRF740 (thanks to the 4093 delivering Vcc on its output when HIGH, I'd guess). 12V would be optimal.3. Usually a fast diode (UF4004) is recommended for D3 (vs 1N4007).4. FYI for future nixie projects, you can useULN2003s + 47V zener on its COM pinrather than discrete MPSA42s+resistors. When off, the voltage across the cathode is about 123V which isn't enough to light it.

author: oz2cpu
author_rank: Frequent Contributor
timestamp: June 02, 2025, 02:00:19 pm
content: the classic kicad way of making unreadable and hard to understand schematics,here is my suggestion about how to make the schematic as easy to read, as fast as possible,hope this input helps :-)the idea of a schematic is to show signal flow of most important signals,I also suggest to add important information, like what is the boost osc frequency,what is the expected HT voltage, it is not regulated, only by the pwm ratio,it is very easy to add a voltage feedback regulation, by addting a transistor

author: oz2cpu
author_rank: Frequent Contributor
timestamp: June 02, 2025, 02:24:48 pm
content: the PWM osc and fet driver is designed directly wrong,you have a signal with slow rise-falland put this signal into 6 schmitttriggered inputs, and then paralleled all 3 outputs,it is impossible for all 6 inputs to have exactly the SAME trigger levels and speed..so at eash shift they fight against each other to win the output,you must use only one gate to make the osc, and only one input can be used,see attached here, the best way to make the osc, and also a better fet driver,where the rise fall is now super fast, into the two paralleled gates,now you will see that ic runs a lot colder

author: ppTRN
author_rank: Regular Contributor
timestamp: June 02, 2025, 03:29:14 pm
content: Thank you all for your feedbacks.Yes I must admit that the schematic could be better organized, I layed it down without being to concerned about its readability.This is the first time I design a boost converter and I am actually surprised it works so well. For next version I will try and design a boost based on 555 with proper feedback.About the parralel gates, everything actually runs smooth and cold, I do not think the gates suffers too much the mismatch in the switching timing.Clearely the solution you proposed is better, but I do not think that paralleling them will lead to damage.Thanks tho, here's a video of the device:https://youtube.com/shorts/nGjbAEZnVhA