Why driver ICs?

[allen lutins]

Another nixie newbie here hoping y'all will show compassion for my ignorance.

I have been an amateur electronics hobbyist since childhood, mostly analog (primarily audio & RF-related). I've started playing with some ZM1000s, and built a simple tester to plug them in & cycle manually through all the digits (image at www.lutins.org/projects/nixie1.gif). This is a simple device, with the positive side of a 170V power supply connected to the anode and the negative side switched between digit cathodes. I am not using a driver IC, and here is my primary question: What is the main purpose of a driver IC?

If i understand the specifications properly, 170V is an "ignition" voltage, after which a 125V "maintaining" voltage can be used. Does a driver IC have anything to do with this, or is this another issue entirely? And will i shorten the life of my nixie by supplying it continuously with 170V?

Thanks in advance for helping me merge onto the nixie highway!

-allen

[Charles MacDonald]

On 13-02-01 10:44 PM, allen lutins wrote:

> This is a simple device, with the positive side of a 170V power supply
> connected to the anode and the negative side switched between digit
> cathodes. I am not using a driver IC, and here is my primary question:
> What is the main purpose of a driver IC?>

the main purpose of the driver IC is to decode a BCD (or otherwise)
value to the 10 (or more) cathodes of the Nixie. It also does some
shifting from the 5V range of digital IC logic to the Higher voltage of
the Nixes.

> will i shorten the life of my nixie by supplying it
> continuously with 170V?
>

Is you supply CURRENT limited? Nixies work like Neon Bulbs. (they are
basicaly a fancy Neon lamp)

Once they fire, the current flow will increse, and the drop across the
tube goes down to the maintaining voltage. The standrd trick is to have
a resistor. Beofore the current starts to flow, the resitor having no
current will pass the entire voltage, once the current starts it will
take the "difference" between the Starting voltage and the maintaining
voltage. Without it the current will increase and the tube will
disaapte a lot more power then it was intended to handle.

Find a copy of the "GE Glow lamp Manual" (sometimes seem online) for a
full discussion of the principles.

--
Charles MacDonald Stittsville Ontario
cm...@zeusprune.ca Just Beyond the Fringe
http://Charles.MacDonald.org/tubes
No Microsoft Products were used in sending this e-mail.

[chuck richards]

Hi Allen,

Welcome aboard! Nixies are very enjoyable things to
work with.

First off, you need to have a current-limiting resistor
in series with your 170 volts!!! 15k is a good nominal
value to start with.

Most nixies of that size need to have their current limited
to around 2 or 3 milliamperes. A real nice old book to
have that explains the 74141 driver ic is Don Lancaster's
"TTL Cookbook". You can find a copy from most used booksellers
for fairly cheap.

Basically you can rough out the nixie current by taking
the power supply voltage minus the strike voltage and
dividing that by the resistance value.

In this general case those numbers would be 170 minus 150
which is 20 and then divide that my 15,000. That comes
to .0013 or 1.3 milliamps.

If you'd use 10K then those numbers would be 170-150=20
then 20/10k =.002 or 2 milliamps.

All nixies have a data sheet that shows the recommended
power supply voltage, the average strike voltage, and the
recommended current, and the recommended series resistance.

But you MUST have the series resistance otherwise you will
overdrive the nixie and ruin it very very fast!

The driver ics such as 74141 use a 5 volt supply and have
4 binary inputs. They have 10 single outputs which connect
directly to the tube cathodes. The cathodes are the digits.
Meanwhile, the tube ANODE goes to the series resistor (15k
for starters), and the other side of that resistor goes to
the +170 VDC power supply terminal.

The 5 volt DC power supply that powers the driver ic
is on a COMMON negative ground with the 170 volt supply.

What happens is that when the proper binary code is
applied the the 1-2-4-8 inputs on the 74141 ic, the
appropriate 1-of-10 output gets switched to the common
ground, turning on the nixie digit. It will drop to
within a few volts of ground.

Those 10 outputs on the driver ic are capable of
handling about 55 volts and that is enough to make them
safe to use on nixie cathodes.

Be extra careful never to short any of the 5 volt pins
to any of those ten pins that are connected to the nixie
cathodes. Any short, however brief, will INSTANTLY destroy
this ic. Beware also the 5 volt power input pins on this
old ic are pins 5 and 12! Be careful!

That is the quick general explanation. More detailed
in depth reading can be done by finding the exact tube data
sheets and by looking over the 74141 data sheet.

There is also 7441, which was an earlier version.
And also the rare 74142, which has a decade counter built in.

There are Russian equivalents of the 74141 available on
ebay.

Hope this helps some.

Chuck

---- Original Message ----
From: alle...@gmail.com
To: neoni...@googlegroups.com
Subject: [neonixie-l] Why driver ICs?
Date: Fri, 1 Feb 2013 19:44:37 -0800 (PST)

>Another nixie newbie here hoping y'all will show compassion for my
>ignorance.
>
>I have been an amateur electronics hobbyist since childhood, mostly
>analog
>(primarily audio & RF-related). I've started playing with some
>ZM1000s, and
>built a simple tester to plug them in & cycle manually through all
>the

>digits (image at www.lutins.org/projects/nixie1.gif). This is a

>simple
>device, with the positive side of a 170V power supply connected to
>the
>anode and the negative side switched between digit cathodes. I am not
>using
>a driver IC, and here is my primary question: What is the main
>purpose of a
>driver IC?
>

>If i understand the specifications properly, 170V is an "ignition"
>voltage,
>after which a 125V "maintaining" voltage can be used. Does a driver
>IC have

>anything to do with this, or is this another issue entirely? And will

>i
>shorten the life of my nixie by supplying it continuously with 170V?
>

>Thanks in advance for helping me merge onto the nixie highway!
>
>-allen
>

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[allen lutins]

Thanks for the replies folks! I do know about the importance of current limiting (based on the research I did before building my tester), but I forgot to mention that I *did* indeed include a series resistor...however, I calculated the resistance based on a current limit of 20-30 mA, rather than the lower limit someone suggested; I'll have to review the specs for my ZM1000's and verify the basis of my decision.

I hope to develop some more complicated (for me, anyway) devices soon, and sure appreciate having the support and wisdom of this group :)

-allen
KC2KLC

[chuck richards]

Hi Allen,

There are several sources of data sheets online for various nixies
and also for the driver ics. Don Lancaster's books
"The TTL Cookbook" and "The CMOS Cookbook" are great references
that explain a lot about using digital logic ics.
If you want to build a nixie clock from scratch the old
way using discrete logic ics, these books are a great guide
to methods.

http://www.wps.com has quite a few nixie and driver
ic datasheets.

By the way, you have a great web site! Fascinating!
I read the article you have the link to about the
crew cabin of space shuttle Challenger. And I also like
the things about the "numbers stations"

My website is http://www.richardslaboratories.com
I make wax cylinder recording blanks for Edison cylinder
phonographs.

Chuck



---- Original Message ----
From: alle...@gmail.com
To: neoni...@googlegroups.com

>--
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