logisim-evolution

[newxito]

I always wanted to design a nixie clock that uses just 74xx ICs. I know that there are some schematics available but just copying a design is not fun.

Recently, I watched a video from CouriousMarc with an intro to a digital logic circuit simulation software called logisim-evolution. I think that will be a big help, the software looks great!

[Jeff Walton]

I designed a nixie about 50 years ago that used all 74xx logic and a few discrete transistors.  It was wired point-to-point to the IC’s (no sockets) and it ran for 35+ years.  The only logic mistake that I made was that I did the AM/PM indicator and was all proud of it and someone pointed out to me that PM changes to AM at midnight, not 1 AM.  It was going to require all new logic and I never changed it but it sure was unique.  I used mains frequency division and a 74123 as a monostable-one shot timer for the input to the frequency counter to eliminate line noise.  That resolved all of the noise issues, which were a real pain until I did that.

 

It was a wonder that I didn’t damage the ICs by soldering directly to the pins and using old telephone twisted pair wires for the connections.  I was a poor college student and scrounged everything I could find…

 

Jeff

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[tntmod54321]

I guess my phone has the same 12am error then, im pretty sure that 12am is correct as stupid as it is.

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[Ian Vine]

Clip from Wikipedia https://en.m.wikipedia.org/wiki/12-hour_clock#Confusion_at_noon_and_midnight

If you read on there is a fair bit of confusion around 12am and 12pm

Ian

It is not always clear what times "12:00 a.m." and "12:00 p.m." denote. From the Latin words meridies (midday), ante (before) and post(after), the term ante meridiem (a.m.) means before midday and post meridiem (p.m.) means after midday. Since "noon" (midday, meridies (m.)) is neither before nor after itself, the terms a.m. and p.m. do not apply.^[2]Although "12 m." was suggested as a way to indicate noon, this is seldom done^[20] and also does not resolve the question of how to indicate midnight.

On 21 May 2021, at 23:22, tntmod54321 <tntm...@gmail.com> wrote:



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[J Forbes]

I dind't design the logic myself, I used a design from the TTL applications book by Texas Instruments. But the clock is still around, twenty years later. I don't leave it running, it's kind of scary.

http://selectric.org/nixie/index.html

and scroll down to the bottom of the page

[newxito]

Small typo sorry, the youtube channel is called CuriousMarc....

My "creepy clock" from 2016 still works and I turn it on from time to time, but only while I'm in the room :-) 

[gregebert]

My first nixie clock uses 4000-series CMOS, and is AC-line powered. Not just the power ( without a transformer), but also the timing. There is a battery-backup oscillator. I built 2 in 2011, and our 2 kids each built one. All 4 are still running just fine. They can display 12hr or 24-hour mode.

I simulated the design in verilog so there were no logic errors or fixes on the PC boards.

[newxito]

No transformer? Well, that's scary indeed :-)

I almost don't dare to ask... does it have a fuse?

[gregebert]

The AC input has 2 fuses (3/8 amp fast-blo on the hot and neutral lines), and 2 resistors (33 ohm, 1/4 watt). Any one of them will blow to open the circuit (never happened). Yes, it's a hot-chassis design but so are many other devices. There is sheet-metal shrouding to protect from an internal fire (never happened).

I always suspected you could safely run CMOS IC's directly on the AC line, and that was one of the goals of the design, not just to build a nixie-tube clock. I also did all of the CAD work (PCB design, logic simulation, schematic capture)  with free software on a PC that I literally had thrown into the trash, but had second thoughts because I knew that PC still had a useful purpose (it's 19 years old now, and still running....). That was another design goal.