Wanting to build a Nixie Calculator

[nzoomed]

Have built a small Nixie clock about 30 years ago. worked well but used the 74141 chips in a non multiplexed way.
I have schematics somewhere how to built that.
As far as I know Nixies don't like multiplexing as it takes a few milliseconds for the Neon gas to ignite in the tube.

Im not too sure what the story is with multiplexing nixies, but many seem to do it nowdays with their clocks after it was figured out how to do so.
I can see the reasons why, it makes the footprint smaller on the PCB. I would prefer each tube individually driven though.

 

[BobW]

Yes, multiplexing of Nixies is certainly done. I've seen a number of Nixie clock demos on YouTube that are multiplexed. Multiplexing simply looks like pulsating DC to a Nixie. When a Nixie fires, it generates some transient RFI, but not when it's glowing steadily with DC on it. I avoided multiplexing my Nixie displays for this reason, because I was operating radio equipment nearby and didn't want the interference. There may also be other reasons not to use pulsating DC on Nixies. Perhaps shorter life?

As for which calculator chip to use, I recommend going with what the others have suggested: use an Arduino or something similar. Trying to use a TMS0103 with Nixies would be a nightmare. BTW, it's long obsolete and probably hasn't been manufactured since the 1970's.

 

[nzoomed]

Yes i know they are no longer produced but many are on ebay.

Arduino could be the way to go, but it appears its very complex to make a decent calculator that can handle functions properly, for example decimal points and division without a remainder etc.

 

[Les Jones]

You could use a normal calculator with a multiplexed LED display (If you can find one as most now use LCD displays.) and use a microprocessor to demultiplex the display and convert the 7 segment data back to BCD. I did something similar many years ago interfacing the first microprocessor (National Semi INS8060) I had with the display and keyboard of a calculator. (Most calculators used LED displays at the time.)
An Arduino should be relativly easy to do the calculation part as they are designed to be programmed in "C" which has lots of maths functions built in. I could not help with programming in "C" as I work in assembler. (Assembler would be easy to do the interfacing but hard to do the maths.)

Les.

 

[Nigel Goodwin]

You could use a normal calculator with a multiplexed LED display (If you can find one as most now use LCD displays.) and use a microprocessor to demultiplex the display and convert the 7 segment data back to BCD.

It's probably easier to just write the entire calculator on the processor

Google finds various examples, including this one:

https://www.microcontroller-project.com/calculator-with-pic16f877-microcontroller.html

Obviously that uses an LCD, but it would be simple to use nixies instead.

 

[Les Jones]

Hi Nigel,
The suggestion was probaly biased as I am useless at programming in "C" but find assembler reasonably easy. (But I would not attempt to do the maths in assembler.)

Les.

 

[spec]

This may be of some interest:
https://www.instructables.com/id/How-to-Control-a-Nixie-Tube-with-an-Arduino/?ALLSTEPS
https://www.instructables.com/id/NIXIE-TUBE-DRIVER-MODULES-Part-II/?ALLSTEPS

TI SN74141 (K155ID1) data sheet: https://neon1.net/nixieclock/sn74141.pdf

spec

 

[Nigel Goodwin]

Hi Nigel,
The suggestion was probaly biased as I am useless at programming in "C" but find assembler reasonably easy. (But I would not attempt to do the maths in assembler.)

Maths in assembler isn't as hard as you might imagine - and you can find plenty of maths routines to download.

Basically you load one value to a variable (a number of PIC registers, depending on the size of maths routine you're using), the other value to another variable, and then call the required maths routine - the result is left in one of the variables, it's really pretty easy.

 

[nzoomed]

Wish i knew how to program in C lol!
I have no experience but want to get into programming micro controllers.

I too thought of the same idea as Les, and de-multiplex the output for an LED display. But if i go to that trouble, i may as well just code the jolly calculator into the arduino if it can be done easily enough, from what projects ive been looking at, it seems people have had difficulty doing a full function calculator on the arduino.
But if it can be done easily enough on the arduino, then you have the benefit of the calculator all on one chip without the need of an extra chip

Im thinking of using 5870 nixies, these are not too big, would be great if i could find a symbol tube for / - + x % etc, but i dont really think its even necessary, but would add a bit of a wow factor.

 

[spec]

http://www.vintagecalculators.com/html/build_a_retro_calculator.html

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http://smithsonianchips.si.edu/augarten/p38.htm

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[nzoomed]

http://www.vintagecalculators.com/html/build_a_retro_calculator.html

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http://smithsonianchips.si.edu/augarten/p38.htm

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That chip does look much better, Im trying to work out if this is designed to use with a multiplexed segment display or not.
If not, then i guess it would be pretty simple to use with nixie tubes, although i would need to use 9x 74141 chips (one for each nixie) if i dont multiplex them.

One question, i dont see any output pins for the decimal points. My nixies have decimal indicators on them, so how are the decimals handled?

 

[KeepItSimpleStupid]

One question, i dont see any output pins for the decimal points. My nixies have decimal indicators on them, so how are the decimals handled?

You can take another BCD to decimal decoder and use that to operate the decimal. Only one it lit at a time usually. e.g. 00 is this decimal 111. and 01 is this "11.1" one etc.

 

[spec]

That chip does look much better, Im trying to work out if this is designed to use with a multiplexed segment display or not.
If not, then i guess it would be pretty simple to use with nixie tubes, although i would need to use 9x 74141 chips (one for each nixie) if i dont multiplex them.

One question, I don't see any output pins for the decimal points. My nixies have decimal indicators on them, so how are the decimals handled?

As shown in the schematic below, from the National MM57459N calculator chip data sheet, the output to the display is multiplexed and includes a decimal point (DP). The output encoding is for a National NSA1188 7 segment 8 character LED display. **broken link removed**

I can't find a problem with multiplexing Nixie tubes apart from possible audio noise from some of the bigger Nixie tubes?

spec

 

[BobW]

I guess that converting from 7 segment drive to decimal isn't insurmountable. Here's one solution:
http://www.mcamafia.de/nixie/ncp_en/nix_deco.htm

 

[nzoomed]

As shown in the schematic below, from the National MM57459N calculator chip data sheet, the output to the display is multiplexed and includes a decimal point (DP). The output encoding is for a National NSA1188 7 segment 8 character LED display. **broken link removed**

I can't find a problem with multiplexing Nixie tubes apart from possible audio noise from some of the bigger Nixie tubes?

spec

View attachment 100959​

Yes thats correct, apparently RF noise can be an issue.

As far as using 74141 chips, these are not designed for a multiplexed BCD signal, so i could not connect these directly to the output of the NSA11887 as far as im aware?

 

[Les Jones]

Although 74141s were not designed for multiplexed displays I think they would switch fast enough to work. You would need transistors (A PNP one with it's emitter connected to the positive high voltage supply driven by an NPN transistor.) to provide digit select to the nixie anodes. Another solution would be to demultiplex the signals using a 4 bit latch driving it's own 74141. The data inputs od all the latches woyld be in parallel and they would be cloached with the digit select signals.

Les.

 

[spec]

I guess that converting from 7 segment drive to decimal isn't insurmountable. Here's one solution:
http://www.mcamafia.de/nixie/ncp_en/nix_deco.htm

Nice find Bob.

spec

 

[spec]

This is looking like an interesting and doable project now. I think the hardest part will be designing/constructing the mechanics: case, keyboard, Nixie mounting.

But don't forget that the display of the negative sign still needs to be sorted

It would be great if someone would also do a microprocessor version as Nigel suggested.

spec

PS:I hope we are going to see a pic of a working Nixie calculator soon.

 

[nzoomed]

Nice find Bob.

spec

Yes i was reading that page, he was using a programmed eeprom to do the work, but a arduino would be easier today...

 

[nzoomed]

This is looking like an interesting and doable exercise now. I think the hardest part will be designing/constructing the mechanics: case, keyboard, Nixie mounting.

But don't forget that the display of the negative sign still needs to be sorted

It would be great if someone would also do a microprocessor version as Nigel suggested.

spec

PS:I hope we are going to see a pic of a working Nixie calculator soon.

Yes your right about that, could find another indicator tube to use or else just program an arduino to do it without the -