开云体育

Hello everyone.
Through eBay, I've bought a few switching power supply units for nixies. They seem to be based on the Desmith design. For now, I just intent to use them to light up and test nixies.

It works perfectly, puts out exactly 180 volts. I noticed that the nixies shine quite bright, so I wonder if I should be using some resistor (and, if so, what value) in series with the anode to avoid damage.

Thanks

Marco

[snip[

I wonder if I should be using some resistor (and, if so, what value) in series with the anode to avoid damage.

a 12Kohm should do fine :) Its what's suggested in the documentation
I've read (Burroughs mostly)

--
Morgan gangwere

“The future’s already arrived. It’s just not evenly distributed yet.”
William Gibson

"cagamba" <cagamba@...> wrote:

I wonder if I should be using some resistor (and, if so, what value) in series with the anode to avoid damage.

Hello Marco,

Yes, you should. Look at the datasheet(s) for your nixie(s) to see what the recommended current should be, then calculate the anode resistor size. Sometimes the datasheets will even make suggestions as to the appropriate value(s) for certain supply voltage(s).

Regards,
Vince

At 6:18 AM +0000 12/25/09, cagamba wrote:

Hello everyone.
Through eBay, I've bought a few switching power supply units for nixies. They seem to be based on the Desmith design. For now, I just intent to use them to light up and test nixies.

It works perfectly, puts out exactly 180 volts. I noticed that the nixies shine quite bright, so I wonder if I should be using some resistor (and, if so, what value) in series with the anode to avoid damage.

Thanks

Marco

Marco,

Yes, a series resistor is mandatory. You wouldn't run an LED without one, and a nixie tube works just like an LED as far as its voltage/current relation is concerned.

The value depends on the current you want to push through the tube and the voltage across the nixie tube when lit. This is usually 140 volts. If the power supply puts out 180 volts, then the resistor will have 40 volts across it, being the difference between the 180v supply and the 140 volt tube.

The tube current depends on the tube size. For a typical 15mm digit height, use about 3 milliamperes. Use 2 mA for a 10mm digit, and 5 mA for a 30mm digit.

Ohm's law says that 40 V / 3 mA = 17K ohms. Round it up to 18K or 22K whatever you have handy.

Using that resistor as a first guess, connect it and measure the actual voltage across the resistor. Adjust the formula to match, and you will have the correct value.
--

--David Forbes, Tucson, AZ

Yes, as everyone else has already said, it's absolutely
required that a nixie tube has a series resistor!

This is usually put in series with the anode (positive)
lead.

They will be wrecked in very short (pardon the pun) order
without such a resistor.

On one of my 175 volt DC power supplies, I have a 20 position
barrier strip to which are screwed several resistors ranging
from around 10k up to 47k or so.

The tiny little tubes such as NL5853 will glow fairly well
using the 47k or maybe 33k.

More standard sized tubes such as NL941 glow nicely with
around 20k to 15k.

Some of the larger tubes need down around 10k or so.

But, do go by what David Forbes says about current.
You will find that my ballpark resistance values do tend
to agree with David's specified currents.

Chuck

[Shine quite bright...the understatement of the year 2009...]
:P

nixies shine quite bright, so I wonder if I should be using some
resistor (and, if so, what value) in series with the anode to avoid

$4.95/mo. National Dialup, Anti-Spam, Anti-Virus, 5mb personal web space. 5x faster dialup for only $9.95/mo. No contracts, No fees, No Kidding! See for more details!

--- In NEONIXIE-L@..., "chuck richards" <chuckrr@...> wrote:

[Shine quite bright...the understatement of the year 2009...]
:P

LOL! "should, mandatory, absolutely required..."
I see my sin. Would it be overkill to build a variable resistance "box" (using decade switches) to accomodate the requirements for all the tubes I have? Or maybe just use a sliding variable resistor ('potenciometer')? Maybe it's more practical to use just individual resistors, I know.

Here's one for sale on someone's webpage, perhaps it might be of interest to someone here. Item 233. Price of $75 is seemingly attractive, considering it's all metal ("built like a tank", he says) and you'd take home a matching variable capacitance box too. Guy calls himself a packrat, and I agree. A few other interesting items for sale there too - nothing nixie though.

At 4:33 PM +0000 12/26/09, cagamba wrote:

--- In NEONIXIE-L@..., "chuck richards" <chuckrr@...> wrote:

[Shine quite bright...the understatement of the year 2009...]
:P

LOL! "should, mandatory, absolutely required..."
I see my sin. Would it be overkill to build a variable resistance "box" (using decade switches) to accomodate the requirements for all the tubes I have? Or maybe just use a sliding variable resistor ('potenciometer')? Maybe it's more practical to use just individual resistors, I know.

A 4.7K resistor in series with a 50K pot would be just fine. Be sure to use a plastic knob with a recessed set screw, as there may be high voltage on it.

--

--David Forbes, Tucson, AZ

On Saturday 26 December 2009 09:33:19 am cagamba wrote:

LOL! "should, mandatory, absolutely required..."

its like, in the Nixie User's Bible somewhere :)

I see my sin. Would it be overkill to build a variable resistance "box"
(using decade switches) to accomodate the requirements for all the tubes I
have? Or maybe just use a sliding variable resistor ('potenciometer')?
Maybe it's more practical to use just individual resistors, I know.

Not really -- but there's a better way. have on hand a dip-12 socket? Some
assorted resistors? Cool!

Here's how I do it:
(make sure you view things in fixed width :) )

power in Dip12 socket
vcc o-----------[ ~~ ]-.
.-[ ~~ ]-'
`-[ ~~ ]-.
.-[ ~~ ]-'
`-[ ~~ ]-.
.-[ ~~ ]-'
`-[ ~~ ]-.
.-[ ~~ ]-'
`-[ ~~ ]-.
.-[ ~~ ]-'
`-[ ~~ ]-.
-[ ~~ ]-'

Simply shove the appropriate resistors into it (You dont /have/ to use a
DIP12, a DIP8 or some such works fine too) and use the next down hole. $1 in
parts.

As well, a potentiometer would be fine too -- something like a 30k +/- 40%
would do the trick:
12K Resistor
vcc o--~~~--.
==[]---+------o vout
`--/

(a little better is to use the grounding line from the pot down to your ground
like so)
12K resistor
vcc o----~~~-.
[]-----o nixie HV
gnd o--------+------o nixie ground

If you look hard enough he also has some assorted and sundry computer stuff
(including some old FPSs) Neat stuff.

Morgan Gangwere
"The future is here, its just not evenly distributed yet!"
-- William Gibson
"When in doubt, walk up to the offending machine and state Ohms
law: 'v=ir..v=ir'. then hit it. hard. they can smell fear."
(Unknown, presumed from The devil's DP dictionary)

--- In NEONIXIE-L@..., David Forbes <dforbes@...> wrote:

A 4.7K resistor in series with a 50K pot would be just fine.

Thanks everyone who chipped in, I'll try not to fry any tubes. ;)

So... under this arrangement (resistor+pot) I should start with the lower current and, measuring the voltage across the lit nixie, bring it up to the specified voltage? Is that it?

Another question, what's the difference between supply and maintaining voltage, present in nixies' specs? And which one should I use...?

At 4:48 AM +0000 1/4/10, cagamba wrote:

--- In NEONIXIE-L@..., David Forbes <dforbes@...> wrote:

A 4.7K resistor in series with a 50K pot would be just fine.

Thanks everyone who chipped in, I'll try not to fry any tubes. ;)

So... under this arrangement (resistor+pot) I should start with the lower current and, measuring the voltage across the lit nixie, bring it up to the specified voltage? Is that it?

Another question, what's the difference between supply and maintaining voltage, present in nixies' specs? And which one should I use...?

The striking voltage is what starts the current flowing. It's often rated at 170V, but will increase in the dark, or in the cold, or with age of the tube. Not much current flows at this voltage, since the tube drops to the maintaining voltage as soon as it strikes. you design the power supply to provide more than this voltage.

I usually use 190V. 180V is a minimum for reliable operation. The higher your power supply voltage, the more power you waste in the resistor, but the longer the tubes will operate in years.

The maintaining voltage (~140V) is what keeps the gas ionized once it's already ionized. This is what you design the anode resistor to drop the voltage to at the rated current.
--

--David Forbes, Tucson, AZ

So, in this resistor-pot arrangement, do I need to keep an eye on the current flowing through the circuit or the voltage across the resistor? Or would just Ohm's Law take care of the other once one is monitored?

The reason why I ask is because both current and voltage are specified for each type of tube, and I want to build a permanent arrangement for lighting up nixies, using a beat-up multimeter I have to monitor things up - but I don't know wheter to place it in paralel with the resistor to measure voltage or in series with it to measure current.

One other thing, is there a way to measure current without interrupting the circuit?

Sorry for the many basic questions!

I would put the meter reading voltage across the resistor, remember ohms law V=IR
you know R and you can measure I so can work out I.

that way you do not break the circuit to measure. also if the resistor begins to smoke is another way :)

Dean

--- In NEONIXIE-L@..., "cagamba" <cagamba@...> wrote:

So, in this resistor-pot arrangement, do I need to keep an eye on the current flowing through the circuit or the voltage across the resistor? Or would just Ohm's Law take care of the other once one is monitored?

Yes, Ohms law will take care of the other measurement. So measuring the voltage across a known resistance will give the current using the formula I = V / R. So for example if 40V is measured across a 10Kohm anode resistor the current flowing through the resistor (and therefore through the nixie tube) would be 40 / 10,000 or 0.004A (4mA).

The only thing to watch out for is the tolerance of the resistor used and the accuracy of the meter. However, nixie tubes are usually fine as long as the current within a certain range.

The reason why I ask is because both current and voltage are specified for each type of tube

The specified tube voltages are used for working out the power supply voltage required and for calculating the anode resistor value required to give a particular current. The specified firing/ignition voltage determines the absolute minimum supply voltage that can be used to ensure the tube will light up (Typically using a little more than this is recommended as it provides better current regulation). The sustain/maintaining voltage can be used work out the voltage drop across the anode resistor. For example, if the power supply voltage is 180V and the maintaining voltage is 140V the anode resistor will drop 40V (180V - 140V). If the desired tube current is 3mA then the correct anode resistor can be calculated (again using Ohms law) as 40V / 0.003A or 13,333 ohms. No one makes a resistor with that exact value but it only has to be close such as 12K ohm.

- HTH, Tristan

At 11:50 AM +0000 1/4/10, cagamba wrote:

So, in this resistor-pot arrangement, do I need to keep an eye on the current flowing through the circuit or the voltage across the resistor? Or would just Ohm's Law take care of the other once one is monitored?

The reason why I ask is because both current and voltage are specified for each type of tube, and I want to build a permanent arrangement for lighting up nixies, using a beat-up multimeter I have to monitor things up - but I don't know wheter to place it in paralel with the resistor to measure voltage or in series with it to measure current.

One other thing, is there a way to measure current without interrupting the circuit?

Sorry for the many basic questions!

You seem to be answering your own questions, which is a good sign that you know what you're doing but do not realize it yet.

As you suggest, Ohm's law says that the voltage across the resistor equals the current through it times its resistance, so monitoring either gets the same result.

A voltmeter is easier to connect, since you don't have to interrupt the circuit.


--

--David Forbes, Tucson, AZ

g7pkf wrote:

I would put the meter reading voltage across the resistor, remember ohms law V=IR
you know R and you can measure *V* so can work out I.

FTFY.
"Remember kids, its V/IR" "Huh?" "Like this":
V V=IR
I R I=V/R R=V/I

... always helped me. I keep it written on white boards when I work on such things, and there's a few versions written with a circle around it.

--
Morgan Gangwere

Morgan Gangwere wrote:

g7pkf wrote:

I would put the meter reading voltage across the resistor, remember ohms law V=IR
you know R and you can measure *V* so can work out I.

FTFY.
"Remember kids, its V/IR" "Huh?" "Like this":
V V=IR
I R I=V/R R=V/I
... always helped me. I keep it written on white boards when I work on such things, and there's a few versions written with a circle around it.

or course one of our local distributors must make it confusing...

although their logo is still in the cute catagory.


--
Charles MacDonald Stittsville Ontario
cmacd@... Just Beyond the Fringe

No Microsoft Products were used in sending this e-mail.

Charles MacDonald wrote:
[snip]

or course one of our local distributors must make it confusing...

although their logo is still in the cute catagory.

Dang this place treats customers right. Free resistors?!?! Dang :D

--
Morgan gangwere
"Approach with confidence; They can smell fear. Recite Ohms law: V=ir; V=ir;. Hit it, firmly and quickly."
(Excerpt from The Devil's DP dictionary)

snip

So, in this resistor-pot arrangement,

snip

I still say from my experience testing many different kinds
of nixie tubes, that the simplest, most direct, and nearly
the most foolproof way to do it is to bring your 170 volt dc
positive lead out to a long screw-terminal type of a barrier
strip.

The whole works, power supply and all can be mounted on a
pine board, with the barrier strip across the front. I used
a 20 terminal one.

On that, I have a variety of fixed resistors screwed down
on one end, with the other ends sticking out.
The back terminals of the barrier strip have a bare copper
wire threaded through them all to put them in parallel, and that
is connected to +170 VDC

When I want to test a nixie tube, I clip a black clip lead
to the negative side, and a red clip lead to the resistor
of choice. For average sized tubes like NL 841, I usually start by
selecting
the 20k resistor. For tiny tubes like NL 5853, I'll start at about
47k, and work down. Clip up the black (-) lead to the digit
being tested and clip the red clip lead with the selected resistor
in series to the tube's anode.

Clip it up, turn on the supply, and measure the voltage
across the resistor.

Make a table of all the digits, because they do vary.

The trouble I see coming with the potentiometer idea
is that you'll be lost as far as knowing what the resistance is.
You'll have to shut it off to measure the resistance.

My two cents worth is: get about a 1:1 isolation transformer,
and use a full wave rectifier. Then, filter that DC a little
bit with a cap. I used an old motor start cap. It's 12 uF
at 330 volts ac. That kind of a supply makes 170 volts DC.
It's rugged and simple to make.

I would also steer clear of any clock circuits that use
non-isolated high voltage power. That is asking for trouble.
That is begging for wrecked logic chips. Don't do it.
Avoid that like the plague. Use an isolation transformer.

Chuck


$4.95/mo. National Dialup, Anti-Spam, Anti-Virus, 5mb personal web space. 5x faster dialup for only $9.95/mo. No contracts, No fees, No Kidding! See for more details!

--- In NEONIXIE-L@..., "chuck richards" <chuckrr@...> wrote:

Clip it up, turn on the supply, and measure the voltage
across the resistor.

Is this done before or after the tube itself is connected?

--- In NEONIXIE-L@..., "cagamba" <cagamba@...> wrote:

Clip it up, turn on the supply, and measure the voltage
across the resistor.

Is this done before or after the tube itself is connected?

After. Before the tube is connected, there is no current flowing in
the resistor, so Ohm's law says you would see zero voltage across it.

I think you can feel free to experiment more with your tube.
So long as you have the resistor in series with the power supply, it
should not be easy to damage the tube no matter how you connect it.
One other thing you may want to look out for is, the resistor can
become very hot if both ends get connected directly to the power supply.

Ken