Saturday, February 26, 2011

Kit review – ogi lumen Nixie Tube system

Hello readers

This month we start off with a fascinating kit review  - the ogi lumen nixie tube system. The younger readers amongst us may be thinking “what is a nixie tube?” Here is an example of four in a row:

If you cast your mind back to past the time of LCDs, and past LEDs… nixie tubes were used to display data in various forms on electrical devices, from test equipment, scales, elevator indicators, possible doomsday machines, clocks – anything that required visual output would be a candidate. Although nixie tubes are now totally out of date, as with many things there is a growing trend to use them again, for cool retro-style, nostalgia and those people who enjoy living in the past.

How nixie tubes work is quite simple, an element is within a vacuum tube full of gas, such as neon. When a high-voltage (~190 volts DC) current flows through the element, it glows. For more information, here is a great explanation. You will note that they are similar to in look but different in design to the vacuum-fluorescent displays, as used in the ice tube clock reviewed a few months ago.

The tubes used in this kit are the Soviet model IN-12A:

The IN-12A tube can display the digits zero to nine, with a nice orange glow.  For the uninitiated, sourcing and making nixie tubes can be quite difficult. Apart from procuring the tubes themselves, you need a suitable power supply and logic ICs that can handle the higher voltage to control the tubes. Thankfully Ogi Lumen have put together a system of kits to make using these nixie tubes simple and interesting.

There are three components to the system, the first being the power supply:

Note that the power supply is preassembled. This supply can generate the necessary 150 to 220 volts DC to energise our nixie tubes. Yes – up to 220 volts! For example:

However the current required is quite small – one power supply can handle up to twenty-four IN12A nixie tubes. For those of you assembling these kits, please be careful. It can be easy to physically move the kit about whilst in operation, and touching the live HV pads will hurt a lot. After bumping the HV line on the PCB, my whole left arm went into a spasm and hurt for the time it took to see my doctor. So be careful.

The second item required is the driver kit. This is a board that takes care of the shift-registers and power for two of the nixie tubes. Driver kits can be slotted together to form a row of nixie tubes. The third and final item is the nixie duo kit. This contains two IN-12A tubes, matching sockets and a PCB to muont them. This PCB then slots into the driver kit PCB. You can buy the driver and duo kit as a set for adiscount.

From a hardware perspective, assembling the kits is relatively simple. There isn’t any tricky soldering or SMD to worry about, however you will need a lot of solder. The contents of the duo and driver kits are as follows:

Before you start soldering, please download and take note of the instructional .pdf files available for the duo and driver board kits. Assembling the driver kit (on the right) is very straight forward. However – please read the instructions! An interesting part of note is the K155ИД1IC:

This is the Russian equivalent of the 74141. This is a BCD-decimal decoder IC that can handle the high voltages required for nixie tubes. When soldering the resistors, take care with R2 – it will need to be positioned horizontally so as to not rub against the duo board:

When it is time to assemble the duo board, you will need time and patience. At a first glance, one would imagine that the sockets drop into the PCB, and the nixie tubes will happily be seated into the sockets. This is not so, don’t solder in the sockets first! The pins on the bottom of the socket also form part of the socket for the tube legs – which can alter the positioning of the socket legs. Make sure you have the socket with pin 1 at the top of the PCB. After some trial and error, the best way to insert the tubes is to first partially place the sockets into the PCB:

… then fully insert the tubes into their sockets. Make sure the tube is the right way up – check that the digit 3 in the tube is the right way up. Then push the whole lot into the PCB. At this point you should check to make sure the sockets are in line with each other:

(Notice how thick the PCB is…) At which point you can solder them in, followed by the row of connector pins:

By this stage you will need some fresh air from all that soldering. The PCB holes for the socket pins really take a lot. Now you can connect the power supply to the driver board and give the tubes a test-toast:

All the tubes should have their elements glowing. This is a good start. The next step is to connect the appropriate microcontroller and start displaying. As noted in the instructions, the 74141 BCD-decimal ICs are controlled by standard 74HC595 shift-register ICs, so your microcontroller needs to send out a data, clock and latch line. My following examples have been created using the Ardiuno system and acompatible board.

The first example is a method of displaying integers. It uses the Nixie library which you can download here. Download the example .pde fromhere.

/* Nixie tube demonstration code - function to display an integer
http://tronixstuff.com - John Boxall. February 2011.
Modifed sketch originally created by Lionel Haims, July 25, 2008. Released into the public domain. */
// include the library
#include <Nixie.h>
// note the digital pins of the arduino that are connected to the nixie driver
#define dataPin 2  // data line or SER
#define clockPin 3 // clock pin or SCK
#define latchPin 4 // latch pin or RCK
// note the number of digits (nixie tubes) you have (buy more, you need more!)
#define numDigits 4
int narray[numDigits]; // holds the digits to display
int z=0;
// Create the Nixie object
// pass in the pin numbers in the correct order
Nixie nixie(dataPin, clockPin, latchPin);
void setup()
{
nixie.clear(numDigits); // clear display
}
void nixNum(int z)
// displays integer 'z' on 4-digit nixie display
// keeps leading zero, as blank still flickers somewhat
{
narray[0]=int(z/1000); // thousands value
z=z-(narray[0]*1000);
narray[1]=int(z/100); // hundreds value
z=z-(narray[1]*100);
narray[2]=int(z/10); // tens value
narray[3]=z-(narray[2]*10); // ones value
nixie.writeArray( narray, numDigits);
}
void loop()
{
nixNum(1234);
delay(2000);
for (int q=1234; q<10000; q++)
{
nixNum(q);
delay(100);
}
}

That was just an arbitrary demonstration to get some numbers displayed. Here is a short video clip of it in action:

Now for another, more useful example. By using a DS1307 real-time clock IC with the Arduino, we can make a nice clock that displays the time and date. For more information on using the DS1307 with Arduino, please visit this tutorial. You can download the example nixie clock .pde file from here. And finally, here is the clock in action:

The problem with these tubes is that you will never have enough. Already I have thought of a few things to make that require a lot more tubes, so in the next month or so stay tuned to tronixstuff.com as there will be more projects with these kits.

In conclusion, this was a great kit and anyone looking to use some numerical nixie tubes will do very well with the Ogi Lumen products. Furthermore the designs are released under Creative Commons by-sa-nc, and the files are available to download from the product pages. And finally, it is a lot of fun – people will generally ask you about the tubes as they may have never seen them before.

Remember, if you have any questions about these modules please contact Ogi Lumen via their website.

Higher resolution images available on flickr.

Otherwise, have fun, stay safe, be good to each other – and make something! :)

[Note - the kit assembled in this article was received from Ogi Lumen for review purposes]

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