This is my first Numitron clock, and frankly I'm entirely taken by the elegance and clean lines of the digits presented by Numitron tubes. Probably the whole of the rest of the world already knows about Numitrons, and I'm the last person on earth to discover them, but all the same I'm happy it happened late rather then never.
Numitrons are the seven segment technology from before the time that LEDs became ubiquitous. LEDs were so cheap and robust, and made so few demands on the driving circuitry that they killed everything that came before. This stopped the production of tubes like Numitrons, and nowadays they are becoming increasingly rare and difficult to find. Even rarer are the tubes used in the "NumiQueen", the IV-13 tube, the so called queen of Numitrons. Nixies seem to be still fairly easy to come by in comparison, but Numitrons are the much exotic (and some say more beautiful) cousin. The IV-13's used in the NumiQueen are the largest and most beautiful examples of the already beautiful Numitron.
The technology itself is fairly simple: A filament s driven until it glows red hot in a vacuum, much like an under powered light bulb. Modern filament lamps with a retro look are based on the same idea: A filament glowing warm orange in a vacuum will last for a long time, provided that you run them in the correct way. If you drive them too hard, they can age quickly, and drive them too softly, and they will not glow correctly.
This is the innovation that the NumiQueen brings: The filaments are driven using a regulated constant current driver, meaning that manufacturing tolerances of each filament are rendered insignificant. The problem with driving tube filaments with an unregulated, or even regulated constant voltage driver is that the circuit will place some filaments under stress because they have a lower resistance, leading to a higher current in that filament and shorter overall tube life. The NumiQueen manages the drive current (not the voltage), and therefore adapts the drive voltage to provide the correct current.
Back in the days of tungsten filament light bulbs, you may remember that they usually broke when the light was first turned on, and this is due to the inrush current at the moment of turning the light on while the filament is cold: tungsten filaments have a positive temperature coefficient, and the initial current drawn when the light turns on is higher than during normal usage, because the filament has not reached operating temperate and its resistance is low. After a few milliseconds, the filament heats up and the current falls. However, the inrush current at the moment of turning on is stressful for the filament. Constant current sources don't have this problem: The current reaches the limit level and the filament has time to heat up without being stressed.
Additionally to the current limiting circuitry, the NumiQueen has another trick up it's sleeve: The filaments are pre-heated with a low current before turning them on fully. This further reduces the stress on the tubes.
The NumiQueen does everything possible to preserve the life of these valuable and rare Numitrons. Just because so much emphasis has been given to this doesn't mean that you should worry too much about the life of the tubes: They have a rated life of 50,000 hours, which is about 6 years in constant use. The NumiQueen is clearly trying to extend this already long life by treating them as gently as possible.
I bought the tubes for about $30 dollars each, as the kit came without tubes (there is a kit option including tubes, but I preferred to source them myself), but had to look around to find someone able to sell me the tubes. If this is too much trouble for you, Jürgen at NixieKits can supply the kit with tubes, which means that you'll have an easier time of it.
Brian used to do a size comparison with a standard "Diet Coke" can, but for two reasons that standard device is going to have to be changed. First of all, I don't drink that crap, and secondly the cans where I live are a different size and shape to the ones that used to be used. Perhaps Brian can ship me the standard can that he's been using. I promise I'll only use it for the size comparison and I promise won't drink it. (That was not hard to promise). In the mean time, we'll just have to find another size comparison object.
Here we see the clock built from the parts I received in the kit. As I said, I sourced my own IV-13 tubes. You can see the tiny filigree filaments that there are inside, arranged as a standard seven segment display. There is also a decimal point which you can see on the last digit. Each clock also has a serial number, which you can see on the bottom
The acrylic case is a nice touch as well. It allows you to finish the clock to be something that you can proudly show to others, without having to wait for a case or build one yourself. You can easily build this clock in an evening, right up to and including the case.
There is also a power supply in the kit package, with a plug suited to your country available by selecting the appropriate option on the NixieKits site. I chose the back lights that randomly change colour, so you can see that it looks a bit like a circus, but there are other, more sober options also available when you order.
Another feature that you can just make out in this light is the filament pre-heating. You can see the faint glow of the filaments which are not lit up. This is the controller making sure that they are ready to go without the risk of giving them a thermal shock. This is a great feature and really shows the attention to detail.
There is a separate article about the process of constructing the kit. However it suffices to say that the construction is not particularly difficult, and no special tools are required. Construction time is about 3 hours if you are moderately experienced.
The kit comes complete with a power adapter and a neat and tidy acrylic case, which is a nice touch, meaning that you will have a presentable clock right away at the at the end of the build, which is highly satisfying.
The NumiQueen offers a fairly standard set of features for a tube clock, and if you have previous experience of either a PV Electronics or a NixieKits clock, you will find no surprises here. The NumiQueen is a totally faithful translation of Nixie clock features into a Numitron clock. Normally the features of this firmware doesn't really excite me very much, but along with the Numitrons, it works very well. The Numitrons themselves become the talking point of this clock, not the stunts that the firmware can do.
There are all the normal features you would expect:
The clock has 4 buttons on it, meaning that setting is quite straight forward and logical. One of the buttons is used for turning DST on and off, another is used for managing the alarm, and the last two are used for setting the clock up.
I set up the clock to use an NWTS, and this was really quite easy. Set option 12 to "4" (GPS module) and option 13 to "1" (9600 baud) and that was it. The unit acquired the time right away. I did have to play with the DST settings for a few minutes to make them right, with option 14 set to "0" no hours difference and option 16 set to "1" (add the hours).
I was impressed by the brightness and elegance of the Numitron tubes. It's the first time I have seen them in real life, and it is a learning experience with them. They fit tightly into the sockets on the board, and putting them in for the first time was quite stressful: The new sockets are tight, and the tubes look so fragile. By a process of "wiggling" them in, they fit snugly against the case and all work perfectly. The sockets are really nice, high quality items, but you need to spend some time getting them aligned on the board so that the tubes stand up straight.
In use, they emit some heat: This was worrying at first to someone more used to Nixie tubes, which tend to stay more or less cold, even after hours of use. However, this is normal, and they didn't get so warm that it really worried me. It wasn't clar how much of the heat came from the tubes themselves, and how much came from the driver circuitry.
The time keeping of the clock is of course excellent, especially with the addition of the nwts which is already in my collection, and which seems to work with pretty much everything. The time seems to be consistently up to 1 second out, but the time drift does not get worse over time when using the nwts unit.
Changing from and to DST is easy to do because there is a button and an indicator for it, but there must be a better way to achieve this in 2017. It seems somehow a bit perverse that a high tech time keeping device needs a human to intervene to tell it the time. Admittedly, it's definitely a first world sort of problem, but really? DST rules are being largely simplified, and we're not dealing with a space shot, so a second here or there is not going to kill anyone, but there must be a better way than this.
The NumiQueen is a great product. It is well presented, not that hard to build, gives a really professional looking result, right down to the case. The Numitrons are a bit hard to find, and moderately expensive (but not as expensive as large tubes), but any troubles finding them, and Jürgen can supply the tubes with the kit.
Do I like the NumiQueen? Well I guess that this is already clear: It is my favourite clock of the moment.
Would I recommend to buy it? Yes, if you are looking for something a bit different from the more of less run of the mill Nixie experience, then the NumiQueen is a great answer to that. It's a bit expensive, but it gives a result that is out of the ordinary.