Maximum voltage across Nixie IN-12

[unpleasant_persona]

This is my first post on my effort to build my first Nixie clock from
scratch. I'm currently working on the power supply and am looking to
make a very simple implementation. Being in North America I'm dealing
with a mains voltage of 110V and would like to use a simple voltage
doubler to make the anode voltage. However, I can't find a reference
to the largest potential that can be placed across an IN-12 tube. The
datasheet indicates a striking voltage of 170V and that 2.5-3.5mA is
the driving current once illuminated. I realize that these operate as
current devices having read a few posts (http://groups.google.com/
group/neonixie-l/browse_frm/thread/ea035dab64fa8e43).

Will having 220V (or more) damage the tubes?

If not what is the maximum voltage that can be placed across these
tubes when they are not conducting?

Thanks in advance

[David Forbes]

On 11/19/11 1:28 PM, unpleasant_persona wrote:
> This is my first post on my effort to build my first Nixie clock from
> scratch.
>

> Will having 220V (or more) damage the tubes?
>
> If not what is the maximum voltage that can be placed across these
> tubes when they are not conducting?

Welcome to the wolrd of Nixie clock building! IT sounds like you've done
your homework.

They won't get damaged easily if you have a current limiting resistor.
220V should be just fine. A higher voltage is recommended by Burroughs
in their old data sheets.

You'll waste more power and your anode resistors will run hotter,
however. You would want to use one watt resistors for 220V.

By the way, the typical sustaining voltage across the tube when lit is
150V. The difference from your power supply voltage is all dissipated in
the anode resistor.

--
David Forbes, Tucson AZ

[unpleasant_persona]

On Nov 19, 4:00 pm, David Forbes <dfor...@dakotacom.net> wrote:
> On 11/19/11 1:28 PM, unpleasant_persona wrote:
>
> > This is my first post on my effort to build my first Nixie clock from
> > scratch.
>
> > Will having 220V (or more) damage the tubes?
>
> > If not what is the maximum voltage that can be placed across these
> > tubes when they are not conducting?
>
> Welcome to the wolrd of Nixie clock building! IT sounds like you've done
> your homework.
>
> They won't get damaged easily if you have a current limiting resistor.
> 220V should be just fine. A higher voltage is recommended by Burroughs
> in their old data sheets.

Hi David, thanks for the prompt reply.

That's good to hear. I was looking at implementing a quick and dirty
170V supply with a zener but even at 21mA (6 tubes not multiplexed)
it's almost 5W of power dissipated in the regulator. Since I don't
have to regulate down I just have to worry about the power dissipated
by the current limiting resistor as you mentioned below.

> You'll waste more power and your anode resistors will run hotter,
> however. You would want to use one watt resistors for 220V.

1.47W (6 tubes' current limiting resistors dropping 220-150 = 70V) is
better than the 5W that I was planning to deal with.

> By the way, the typical sustaining voltage across the tube when lit is
> 150V. The difference from your power supply voltage is all dissipated in
> the anode resistor.

Thanks for reminding me about the sustaining voltage. I'd forgotten
that the steady state on-voltage wasn't 170V so I'll have to redo a
few calculations.

There are great plans for a power supply (http://www.ledsales.com.au/
kits/nixie_supply.pdf) that I was considering using but it seemed a
shame to step down from 120 to 12DC and then back up. Although I'm
assuming the design would be much more efficient if I used some decent
switching regulators. I haven't worked through the calculations yet
though. I really do like the idea of keeping it simple though.

Thanks again for your reply.