High Voltage Power Supply for Nixie and Valve Tubes

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Introduction: High Voltage Power Supply for Nixie and Valve Tubes

About: I'm an Italian freelance structural engineer, graphic designer and photographer, now I'm teaching physics in Waldorf high-schools. I always investigate electronics, robotics and science in general, I'm a passi…

Since in last years nixies displays attracted my attention so much that I bought many of them, I finally managed to design a good power supply and my nixie clock is on the way... [UPDATE: done! read instructable here)
With this circuit you can test a nixie display, or power a multiplexed nixie clock. The potentiometer lets you change the output voltage to fit different types of displays (you can obtain from 100V to 300V DC). My prototype has been built on a breadboard, but I also made a pcb from the schematic so you can etch your own board and solder the components.

WARNING: this circuit raises the voltage to deadly 300V so you must avoid to touch contacts while working, I'm not kidding, please BE CAREFUL!

Step 1: The Schematic

To understand the way a circuit can raise voltage from 9V to about 180V I had to make some research in the web, because I'm not so skilled in electronics to design my own circuit. Anyway I merged some information from the most exhaustive sources, and my circuit tries to be simple and efficient, but most of you readers can probably add some revision or advice.
The two best sources, which are must-see, have been arduinix.com (device assembling instructable here) and Threeneuron's Pile o'Poo, and both their circuits are a bit different from mine, since from Arduinix I've taken the NE555 application, and from Threeneuron's the use of a pull-down transistor to improve the efficiency and reduce the mosfet heat. You can also read ian's instructable to better understand working principle and components details. Another source was this document from www.ledsales.com.au.

On Threeneuron's website you also can find informations about the calculations to find the right R36 anode resistance value to limit the current for each type of nixie display. Let's say that 15 Kohm will probably work for 90% of the displays.
Look the notes on the image for more informations about the circuit. 

I also report the explanation of circuit functioning as -max- wrote in his comment:
An inductor is used to create high voltage kickback. This configuration is often found in boost converters, called that because the boost voltage. It works because one can not change the current flowing through an inductor spontaneously, inductors resist change in current. This means when the MOSFET turns on and passes a current through your inductor, the current flowing though it will steadily rise, "charging" it. It will eventually reach saturation where the magnetic flux can no longer increase and the inductor acts like a short. This is sort of like stretching a rubber band or spring. There is a point where you can no longer pull it tighter (otherwise it will break). Once this point is reached (or often just before it), the transistor turns off, and the inductor is allowed to "snap" back. Remember, the current absolutly cannot change instantaneously. so what happens is when the current is removed, the magnetic field in the inductor created collapses and induces a potential across the inductor. This voltage will slam up to infinity until a current flows between the 2 terminals.
However, in the real world, there is stray capacitance within the inductor as well as outside it, especially if a capacitor is connected. This creates a tank circuit, so the output will actually "ring," it is the equivalent to a bell, tuning fork, spring on a string instrument like guitar, etc. This can be seen on an oscilloscope with the probes connected across the inductor. You will see the ringing and even the initial voltage spike, known as a "transient voltage spike." The diode simply rectifiers this spike and transient so the voltage is DC, although quite a dirty one. (The voltage is all over the place as the inductor oscillates) the capacitor smoothes this out, offering a clean DC high voltage to the nixie tube.

Step 2: The Components

Some detail regard the components.
L1 is a fixed inductor 100 uH 1A, threeneuron's lists some similar models of it, and they could be a little different in dimensions, so my pcb has space for long and short components.
R17 and R18 should be 1% accuracy metal film resistors, to achieve a better voltage stability.
D1 has to be a ultra-fast 400V diode, as BAV21, UF4004, UF4007, MUR140, or MUR160 (thanks threeneuron's again).

Step 3: The Pcb

The pcb has been obtained in DipTrace from my schematic. Maybe you can design a better arrangement for components, I didn't etched this board because I'll incorporate the supply circuit in my nixie clock board. There is space for a big heatsink, also if probably you don't need it. In alternative you can lay down the mosfet. On the left you can see the long shape of the inductance alternative. On the lower right you find the Anode and Cathode contacts, where connect the display.
Attached to this step there are schematics, board and the ready-to-print pdf for toner transfer method.

Step 4: The Breadboard Prototype

Otherwise you obviously can insert components on a breadboard and test the circuit.
To build your breadboard prototype follow the schematic (not the board) and start adding the IC (the NE555 in this case), connect one pin at time, adding components when they're needed, then connect other components between them and to Vin and ground. Double check everything before connecting the circuit. Also check that resistors pins don't touch anything else.

WARNING (again): this circuit raises the voltage to deadly 300V so you must avoid to touch contacts while working, I'm not kidding, please BE CAREFUL!

I used a bigger pot to ease the voltage setting, and I left my circuit working with a nixie for some time (maybe half an hour) to test the heat dissipation, and neither mosfet or inductor were warm at all... so I didn't add the heatsink.

Step 5: The Glow in the Dark

Here you can see some different nixie displays, the red glow is very fascinating.
IN-1 are unpopular between hobbyists because they have a shorter life and they're not transparent on the side, but I like them, and once solved the life duration problem they will be great in a nixie clock. Ampoule displays as IN-16 or the very expensive IN-18 are nice, but I love more the top-view nixies as IN-4 and IN-12 (russian tubes had been produced further than american ones, so they're cheaper and easier to find). If you want a exhaustive description about many nixies see here.

Step 6: This Is Only the Beginning

So this is my contribution to anyone wants to build his own nixie clock, or needs a high-voltage power source to light his plasma devices (as in this impressive instructable, or also this other one) or some valve tubes.
Please comment this instructable and help me to improve the design. I'm waiting for some components to finish my clock, so that you will be able to see it very soon, anyway I know that some improvement is certainly needed and V2 of the power supply can born now... 
[UPDATE: my clock is completed and published: https://www.instructables.com/id/simple-user-adjustable-DIY-Nixie-Clock/]

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104 Comments

0
faxl5774
faxl5774

1 year ago

Thanks for this great instructable! I was really glad finding it.

For my purpose I changed some things and iIf you do not mind, I would make some proposals. Perhaps you are interested...

Proposal 1:
I suggest to use a value for C1 for at least 4.7uF otherwise the initial voltage peak will reach up to 350v DC and this might damage your nixies if you switch on and off too often...
Proposal 2:
I would also increase the value of the snubber C4 up to 470pF to reduce more noise from the MOSFET.
Proposal 3:
Last but not least I would reduce resistor value R18 down to 200 Ohm. Otherwise it is likely to get into trouble adjusting your Nixie voltage to the desired value when the value of R17 differs too much from 220k

Simulation also shows, that the inductor sees a current up to 1.6A. Of course for a very short time (round about 10 microseconds), but I prefer to be on the safe side so I use an inductor that can at least handle 2A current...

If you are interested, see the attached screenshot from the simulation!

Regards,
Axel

Simulation.png
0
andrea biffi
andrea biffi

Reply 1 year ago

Thanks for your contribute Axel!

0
rocketmachine.1
rocketmachine.1

Question 1 year ago

How can I convert 3v from a lion cell to power 4 small nixies ? Thanks in advance !!

0
faxl5774
faxl5774

Answer 1 year ago

As you can see in the simulation attached this is fairly easy... Just exchange C3 with a new value of 22nF...

BUT this increases the current throu the inductor up to 3A!!! So you have to change this too.

Last but not least, I would not do this... You will be exchanging batteries all day long... Let´s assume your 4 Nixies need 6mA each at 180V. That makes according to P = U*I 4,32Watts. Meaning that your Cells have to deliver 4,32Watts assuming no loss anywhere else (quite unrealistic). So they have to deliver a current round about 1,4A.

Simulation.png
0
adjie813281
adjie813281

1 year ago

Does it work if using 12 Vdc as input voltage ?

0
andrea biffi
andrea biffi

Reply 1 year ago

Just add an LM7809 voltage regulator, which will drop your voltage to 9V from any source between 12 and 35V. I think that the circuit doesn't work directly with 12V...

0
faxl5774
faxl5774

Reply 1 year ago

You dont need to do this! Your NE555 accepts up to 18V so you can use 12V (which is in my opinion better) directly. Using an LM7809 is waste of energy without any need, except you need some heater. Of course you have to adjust the value of the potentiometer...

Truely spoken, this is exact the modification I made.

I attached a screenshot from the simulation for you.

Simulation.png
0
EdChamberlain
EdChamberlain

Question 1 year ago

Hi! I built this supply several years ago and am looking to use it again for a new project (since its so great!) Im looking to use SMD parts to make it a bit smaller but am concerned about the voltage rating for some of the resistors. It seems that both R15 and R36 will both need to be rated for high voltages - will a 200 V rating be sufficient?

0
andrea biffi
andrea biffi

Answer 1 year ago

Un not sure, but in my opinion you can give a try. Actually it's pulsing current, maybe it will work..

Hello...! I wanted to be the first one to congratulate, and thank you for another great Instructable... ;)

0
andrea biffi
andrea biffi

Reply 2 years ago

Hello Kjetil, I just realized it's you the first guy which congratulated with me about my first at all nixie project! 😀 Wow 6 years ago... That's great!

0
andrea biffi
andrea biffi

Reply 8 years ago on Introduction

Thanks Kjetil! It's really useful in my opinion, high voltage from 9V DC lets you make a bunch of awesome projects, with others also power cathode tubes and geiger counters (also if with higher voltage than my circuit)

0
UKDradge
UKDradge

2 years ago

R5 (the 33K resistor) is superfluous. There's a 5K resistor inside the 555 from pin 5 to Vcc so all you're doing is creating a collector load of about 4,300 ohms. The circuit works fine without it.

0
owen86
owen86

2 years ago

Does anyone know if the 555 has a pin that can enable/disable the PSU output depending if the pin is high or low.
I am designing an Arduino nixie clock and I want the nixie PSU to power up gracefully after the setup code has been initialised. Another added benefit would be a user set schedule to turn on/off the PSU at certain times of the day or night to save nixie tube life.

0
jmood
jmood

8 years ago on Introduction

The founder of the American Radio Relay League was working on a high voltage circuit within an RF amplifier one day. He had BOTH hands within the enclosure, and he touched the wrong thing with one hand, and he other hand provided a direct path to ground. It stopped hi heart and killed him. His name was Hiram Percy Maxim, the inventor of the Maxim gun, an early form of machine gun (similar in some respects to the Gatling gun.). He was also a skilled electronics and radio man. Perhaps he had a moment of distraction. It only takes a microsecond.

High voltage is extremely dangerous, and if you must work with this stuff, keep one hand in a pocket and do not allow a path to ground through your body. Insulated shoes, gloves, tools, and great caution are the order of the day! Don't work on live circuits either.

0
Professor Solderflux
Professor Solderflux

Reply 3 years ago

Oh brother! Just found this old post looking at Nixie clocks, and had to set the record straight. YES, working with high voltage/current is dangerous. NO, H.P. Maxim did not die by electrocution. He died at age 66. falling ill after a trip to California to visit the Lick Observatory in 1936. No, he did not invent the Maxim machine gun. That was Hiram Stevens Maxim in 1883. He did invent the "Maxim Silencer" for firearms in 1908, but HP is most remembered as an American radio pioneer and co-founder of our American Radio Relay League; the ARRL.

Google is your friend...

0
Bindox
Bindox

Reply 8 years ago on Introduction

High voltage is not dangerous. The danger comes when you add any significant amount of current. Doesn't anyone read any of Tesla's experiments and recreate them anymore?

0
jmood
jmood

Reply 8 years ago on Introduction

Tell that to the family of Hiram P. Maxim. Or the hundreds of people who die by accidental electrocution each year.

High voltages can lower the resistance of human skin, and perspiration even more so. "The NIOSH states "Under dry conditions, the resistance offered by the human body may be as high as 100,000 Ohms. Wet or broken skin may drop the body's resistance to 1,000 Ohms," adding that "high-voltage electrical energy quickly breaks down human skin, reducing the human body's resistance to 500 Ohms." - from the page referenced below.

One volt at one amp can kill. 300v at a few milliamperes can kill you.

Tesla worked with high voltage, and had the right equipment, and the brilliant mind that it took to avoid being electrocuted.

I can only say 'bindox' that your assumption is incorrect and NOT supported by scientific and anecdotal evidence. If you choose to do these high voltage projects, I suggested utmost caution. Recklessness in almost any field can kill, electricity can kill quicker.

And of course if you shuffle across an ungrounded carpet and touch a ground, you'll likely experience a 'shock', and it will be extremely low amperage (on the order of about 0.0000001 amps.. It takes only 100mA to stop your heart. If your skin is wet, 120V could be enough to kill you.

All I urge is caution. If you don't use it, expect a possibly foreshortened life.

I suggest you read:
http://www.ask.com/wiki/Electric_shock
and look at the section on lethality of electricity.

0
haas
haas

Reply 8 years ago on Introduction

Without questioning the potential danger of electricity in general I still think that your contempt for 'bindox' comment is not justified.

Bindox statement is absolutely correct and very well supported by scientific and anecdotal evidence. If you rub a balloon on a sweater to make it stick to the ceiling you have a perfect, non lethal real life exampe for very high voltage (several 1000 volts) at almost no current. Alos if your statement was scientifically proven, nobody would be allowed to legally sell AA batteries. They can deliver up to 5 Amps at 1.5 V

0
andrea biffi
andrea biffi

Reply 8 years ago on Introduction

Yeah, but as you noted very high voltage has to have almost no current to not be lethal, so I will be very cautious in declaring that voltage doesn't kill...