THE INFORMATION YOU WILL FIND HERE COULD BE INCOMPLETE OR INACCURATE. THE WEBMASTER, PROJECT COORDINATOR, PROJECT CONTRIBUTORS AND WEB SPACE PROVIDER EXPRESSLY DISCLAIM ALL LIABILITY FOR INJURY OR PROPERTY DAMAGE RESULTING FROM THIS INFORMATION.

High voltages will not just shock you, they will kill you.
Use extreme caution while building, working on and testing.
Always THINK SAFETY! Only YOU can prevent accidents.

If you are in any way unfamiliar with high voltage circuits or are uncomfortable working around high voltages, PLEASE DO NOT RISK YOUR LIFE BY BUILDING THEM. Seek help from a competent technician before building any unfamiliar electronics circuit.

USE AT YOUR OWN RISK: THE WEBMASTER, PROJECT COORDINATOR, PROJECT CONTRIBUTORS AND WEB SPACE PROVIDER EXPRESSLY DISCLAIM ALL LIABILITY FOR INJURY OR PROPERTY DAMAGE RESULTING FROM THIS INFORMATION! ALL INFORMATION IS PROVIDED 'AS-IS' AND WITHOUT WARRANTY OF ANY KIND.

Wear rubber soled shoes to help keep any accidental shocks from passing through your body. Make sure the unit is unplugged and the capacitors are completely discharged before your body or tools come in contact with the equipment you are working on. (Electrocution - A widely misused term, it refers to death by electrical shock. People often say that they have been electrocuted; that is just not possible, they would be dead. You can only be electrocuted once....)

Capacitors can vent (commonly know as exploding). Wear safety glasses when working with electronics, especially when working with capacitors. Wear two pairs the first time voltage is applied to a capacitor after soldering. If you care about what your face looks like, wear a complete face shield. If possible, put a nonflammable plastic box over your work the first time you apply power.

Wear long cotton pants. Solder drips burn through polyester and hurt for weeks. Don't wear pants that cost too much to be ruined with a burn mark.

If possible, work with a friend who knows CPR and knows how to pull the plug from the wall if you forgot to do that first. Do not work on a system, under any circumstances, while it is plugged in. Don't just turn it off and think that's enough. Others have done this and fried things (or themselves!) by accidentally turning the system on while working. You could end up in the hospital or in a wooden box with just the slip of a screwdriver.

Work with a full fire extinguisher in view. Do not put the fires extinguisher where you would have to reach across equipment to get to it.

The case of a capacitor can have voltage on it. Check it with a working voltmeter on both AC and DC before attempting to touch it.

Make sure you can pull the plug from the wall without having to reach over either the equipment you are testing or the test equipment.

Make sure you can exit the room rapidly without passing your equipment or tripping over piles of stuff on the floor should you need to run for it.

Make your own safety assessment. Your design and craftsmanship must be safe for both you and those who enter your house. Do you have any friends, relatives or acquaintances who insist on touching things when they say "what does this do?"

Both old and new parts can be defective. Test them before installing them.

Make your own risk assessment. Read the application notes for the parts you are using.

Watch out for tantalum capacitors. When they vent, they can spew molten tantalum!

• Keep one hand behind your back. A very dangerous path for high voltage is from hand to hand, with your heart in between. It doesn't take all that much to stop your heart at these voltages.
• Use proper probes. About the only thing you should be doing to a live circuit is checking voltages or signals. Get clamping tips for your probes. Clamp the ground clip to ground. With the hand that is not behind your back, use the proper insulating probe tip on your voltmeter or scope. Be sure your voltmeter or scope is rated for at least 500 volts for this project.
• Disconnect the power and DISCHARGE THE CAPACITORS before doing anything to the wiring.

If you use the information in this site to kill yourself, your friends, family members, acquaintances, total strangers, pets, electronic devices or burn down your house, it is not my problem.

I will nominate you for a Darwin Award.

Proceed at your own risk.

Everything started surfing the Internet looking for a cheap LCD display...

I am always been fascinated by computer history (being myself a relatively 'old' programmer), and I have been once more intrigued by some sites that referred to nixies as 'gas displays'. I remembered the old days where pinball machines (and big computers, but I never seen those) used this kind of numerical displays... so I took a look on Ebay... and discovered that there is a growing interest in selling (and buying) Nixies. As it happens for tubes, some are highly overpriced, but outstanding quality and performance can be obtained at a low cost looking at the East Europe sellers. 'Made in USSR' Nixies are cheap, and beautiful...

In a hurry, I bought a whole bunch of them (and dekatrons too)! Till now I used only one... but they do not have an expiry date (almost... more on this later).

After a reasonable wait (be patient... shipping from Estonia or Lituania is not fast as in the USA or central Europe...) a complete IN-xx Nixie set was in my hands. I had to decide which model was best suited for my first project...

The choice has been done looking for a suitable container for my clock. I found a nice wooden box commonly available (it is the box of a commercial perfume!), and I started measuring... and trying to imagine how compact and / or messy the perfboard will be.

At the end I managed to keep the boards clean, compact and not (too) chaotic... separating the HV power supply from the logic, and assembling the whole as a 'sandwich'.

Giving the box dimensions, the Nixie I used has been the IN-14 one.

I took a look over the Internet to find some ideas to obtain a 135V DC from a wall-wart... with a couple of minor modifications to an existing step-up project (I don't remember the site where I found it, so I cannot add any credit...) I came up with this solution, based on the Motorola 34063 DC-DC converter:

The other components I used, except diodes, capacitors, resistors, 15V AC transformer and inductors are:

• the RS405L silicon bridge rectifier instead of a basic 4-diodes bridge (it requires a bit of drilling, because the leads are thicker than the perfboard holes ...)

• the ubiquitous 7812 and 7805 voltage regulators

• an IRF720 400V mosfet transistor

• a BYV27 / 400 silicon diode rated 400V / 2A

This is the result, compact and clean although on a perfboard instead of a PCB:

As usual I choose a 4 Mhz Microchip PIC (16F873) as the heart of the system...

BUT, how about the other components?

Having an old junk PC motherboard, I extracted a DS1287 real-time clock to avoid errors caused by clock divisions on the PIC itself; then I foresaw a 4-Nixie (or more) application, and decided to use a PCF8574 I²C remote I/O expander.

To avoid a myriad of transistors, I bought on Ebay a set of original K155ID1 Nixie drivers (DM7441A compatible; only one used here...)

Then I considered adding a light sensing device, and PWM support to make the nixie brighter during the day, and softer during the night... an OPT101 monolithic photodiode and a couple of 13007 high voltage-fast switching transistors. This feature has NOT been added on the final clock due to the lack of space in the wooden box, but has been extensively tested on a prototype board.

A couple of buttons to set the time and implement a 'test mode'... a LOT of software... and here is my first clock! :

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