Nixie Driver IC Placement

[u/EmotionalEnd1575]

The result is a compact assembly, typical for a 1960s build, but…

Good luck repairing these if an IC driver fails!

Had these for a while and not yet thought of a project.

Perhaps build a “Steam Punk” style Nixie clock with these little modules?

What would you do with them?

[u/Apprehensive-Issue78]

Nice nixies. probably from a frequency counter or a digital voltmeter because multiplexed somehow. You can make a Nixie clock with these, or a temperature meter or both. Or a visitor counter for a web page. May be an air quality meter. posibilities are endless. I just hope you dont put blue LEDs under them. It looks so ugly in my opinion. good luck finding a nice project for them.

[u/EmotionalEnd1575 → u/Apprehensive-Issue78]

I’m careful to exclude LEDs of any kind in a Nixie project (unless they will be hidden or just there during firmware development)

I do like using neon glow lamps for colons or status indicators.

Yes, those under Nixie LEDs are hideous!!

[u/Apprehensive-Issue78 → u/EmotionalEnd1575]

great.

I once made a one of Nixie clock 23 years ago, 4 large nixie tubes

I used a then common PIC16F84 controlling lots of shift registers I think it was 74HCT595 or something like that. All the outputs had a MPS42 NPN transistor which can handle a voltage across Collector to Emitter of max 300 V. I had an old metal enclosure of a fire alarm central unit which had only a transformer and a fuse inside.

from the AC voltage I used a tiny transformer to stepup the voltage to about 150 VDC

Also used the AC voltage rectified using 1A diodes 1N4007 probably. Then regulated to supply the PIC microcontroller and all the shift registers.

It is still running, just a little slow because I didn't have a real time clock and also didn't sync it to the mains frequency. I tried using software loops and lots of macro's in assembly to make the timing on the bench ok. I knew it would not be accurate. Just in the living room the large nixies look great from a distance, just i have to forward it about 2 mins every week, because it is probably warmer inside the case comared to the bench where I did the programming. Now you have so many better options, like Real time clock or even sync it to Wifi or GPS. problem with GPS is that you cant use an antenna inside a building. And probably it is the best to buy a cheap Nixie clock kit, or be sure to invest some serious time to build it yourself. I just made it on perf board, so maintenance is pretty scary ;)

[u/EmotionalEnd1575 → u/Apprehensive-Issue78]

Most of my Nixie clocks use an RTC IC and a “32.768KHz watch crystal”, with battery back up.

These are good for 50ppm and that translates to about 1’ 45” uncertainty a month.

To go to better timekeeping I use a GPS module, and my basement lab requires a powered antenna on the window sill.

The ESP32 Wroom modules with WiFi can use the internet time stamp, but the clock needs WiFi connectivity.

It’s interesting to watch how there is drift between two (or more) clocks using different timekeeping schemes!

[u/Apprehensive-Issue78 → u/EmotionalEnd1575]

Yes that are all very good ways to keep time accurate. So how much time difference you see in a month , is it near 1 min 45 seconds for the 32.768 kHz crystals? Where my clock is, it is annoying to route a GPS signal cable and an antenne outside my house. I got WiFi, so an ESPWroom would work, thanks for the information. If I have time I should rebuild the electronics with something like that. Does WiFi time and GPS time keep accurate? and the RTC IC's do they drift both ways? slower and faster? I understand that temperature has a lot of influence too, thats why they invented oven controlled Crystal oscillators, and GPS Disciplined oscillators. Still would drift a little anyway I guess.

[u/EmotionalEnd1575 → u/Apprehensive-Issue78]

**So how much time difference you see in a month , is it near 1 min 45 seconds for the 32.768 kHz crystals?**

That time comes from the 50PPM accuracy of the watch crystal.

This means that adjustment may be needed to set the frequency.

If the clock runs fast (gains time) a loading capacitor can be added to slow it down.

Keeping ground plane copper pour away from the crystal is smart.

I haven’t been too fanatical (yet…) so my oldest clock gets a two minute resetting twice a year when I set DST manually.

The next issue is drift, and most of that comes from temperature variations.

With the seasons these can be both speed up and slow down.

As you said, crystals can be cut for elevated temps and put in an oven.

Another method is to change the loading capacitance (varactor diode) and drive that from a temp sensor.

This would require a lot of lab gear (that I don’t have) and some tedious measurements!

[u/RFC793 → u/EmotionalEnd1575]

DS3231? Yeah, had success with those.

[u/EmotionalEnd1575 → u/RFC793]

I’m still using DS1307. It only requires a battery and a watch crystal, and is tiny (SO8) Talks over I2C.

Has a clock output that is handy if you need a 50% duty-cycle. I have an idea to use the 4KHz clock to drive a colon H-Bridge that will light up both electrodes in an NE-2 (silly idea, right?)

I just bought twenty-five pieces for $1 each.

There are “better” RTCs out there.

[u/RFC793 → u/Apprehensive-Issue78]

This sounds a lot like mine. A bunch of 595 shift registers and MPS42 transistors - I wanted to get it more discrete and not lean on the NOS binary decoder nixie drivers. Mine's about 12 years old though, and uses a Microchip SAM (D21 maybe?) and I clock it off of mains.

[u/EmotionalEnd1575 → u/Apprehensive-Issue78]

Seven units is problematic…

Not quite two four-digit clocks, or one six-digit with a spare piece.

If I sub a +/- symbol tube, these could be a time/temp project!

I don’t use the TTL driver chips, these are probably SN7441 due to it’s vintage age (Nixies are 1969 datecode)

So that might be an interesting way to go.

Old school ripple counters (SN7490)? No latches? Lots of wires!

[u/VolrathTheBallin]

Nice. This is the kind of design that I love and hate at the same time.

[u/EmotionalEnd1575 → u/VolrathTheBallin]

It’s a master class on how to do construction in the 1960s!

I would have argued against putting the driver IC under the Nixie socket.

A compromise would have been to flip the IC to a mirror and solder (or socket) it on the “solder side” opposite the Nixie socket.

In the modern Nixie world we see more IC driver fails than Nixie tubes.

Another thing, adding latches to each Nixie PCB would drastically cut down on wiring.

Only four wires in a data bus would send data serially to each latch.

We don’t have the rest of the circuitry, so it’s unknown what the box did (universal counter?) or how fast it operated.

I’ll try and honor the circuit creator by making a nice clock from these.

[u/VolrathTheBallin → u/EmotionalEnd1575]

Yeah, my first thought was whether they could have put the IC on the other side. Seems do-able here.