Resurrected NixiSat GPS clock...

[Nick]

I first made this clock back in 2003 - It has 6 x RFT Z568M giant nixies from the 1960s - when I bought them, back in about 1998, they cost 25 euros each - they are now in the region of 400 each (if you can find them) - some on eBay at the moment BiN for USD 425 each - madness...

300 of these clocks were built - it was covered in a feature article in the IEEE Spectrum magazine in July 2003 - pretty much the whole NOS of the tubes was exhausted at that time - one unmodified (old/rubbish DNSS/Navstar unit still in place) clock sold recently on eBay for over USD 4,000...

The clock developed a problem with its Motorola OnCore GPS module in about 2007 and has been in the loft since then - as its a strictly GPS clock, i.e. atomic time accuracy, it is dead in the water without it...

So, the old OnCore unit, CR2032 holder & antennae BNC were removed, the original BNC hole was reamed out to 13mm and an in-line 6-pin mini-DIN female connector mounted into the cavity (its a tight fit), the space for the MAX232 & its 4 capacitors was populated and the PS2 connector wired in (Vcc, GND, RXD, TXD) - a new Haicom HI-204III 20-channel high sensitivity GPS puck plugs into that - the anode resistors were changed to a slightly lower value, the current limit on the HV SMPS was upped by 30%, the PIC was replaced with one with new firmware (more features and support for the new GPS unit), plus a few other minor electronic & cosmetic changes etc. The base is made of satin-lacquered American Cherry and the cover is polycarbonate.

Glad to have it back...

[Radio Fixer]

Its very pretty and a clever piece of design, a nice useful conversation piece that doesn't take up too much room.

Whats the life of the Nixies? If finite then maybe at the almost irreplaceable cost you shouldnt run it 24/7 ?

Gary

[Nick]

Whats the life of the Nixies? If finite then maybe at the almost irreplaceable cost you shouldn't run it 24/7 ?

Later nixies with mercury doping have a life of about 200,000 hours (nearly 23 years continuous) if driven correctly - overdriving a nixie exponentially shortens its life... without Hg, tubes typically last about 5,000 hours.

The concept of "life" with respect to nixies is a complex one - the generally accepted "end-of-life" is when one of the following occurs:

• Emitted light falls to 50% of its peak value (caused by silvering on the inside of the envelope)
  
• "Cathode poisoning" results in significant sections of digits no longer illuminating
  
• Erosion of cathode material resulting in incomplete digits
  
• Mechanical failure causes the device to cease functioning normally
  

The first item is largely dealt with by the use of Hg doping - that also helps the second issue.
The second issue can be reversed by driving the digit at several times its normal current for an hour or so to restore the surface of the cathode.
The second & third issues can be avoided by cycling the digits in a tube on a regular basis (typically at night) with a higher-than-usual current. In addition, physically/mechanically rotating the tubes from right to left every once in a while so that those digits which are over-used, e.g. the tens of hours "1" & "2" and digits "0" through "5" generally, are more evenly used.
The last point is covered by just being careful!

The Hg doping has a side effect - a purple haze around the digits - the red filtering on some nixies removes the purple resulting in a clearer display. Clear nixies are exactly the same as those with the red coating but are designed to operate behind a flat red filter, e.g. in test equipment...

[Radio Fixer]

Thanks Nick, although I shall never build one what with the price of tubes.

A clock I made had a display failure: usual thing the voltage rectifier overheated the tracks. In repairing it one of the digits 'wen' ' and I thought that was it but found a lady in CA with 4 NOS so bought 2. Happy as we like the clock.

   

   

Gary

[Yorkie]

Not all nixies are expensive, any more than all valves are. The demise of their use was quite sudden and the world is awash with millions - especially the Eastern Bloc, albeit it's true that some are rare and consequently highly sought after.

I mentioned in another thread on the forum some time back, which I can't find now, that I made two 4 tube nixie clocks on PCBs obtained from the States having spotted them on Mike Harrison's splendid 'Mike's Electric Stuff' website. (I'd been given a dozen GN6 nixie tubes and had search for a nixie clock design which wouldn't tax my brain too much!).

Details of the clock and PCB can be found here:

http://www.electricstuff.co.uk/nixclock.html

http://www.electricstuff.co.uk/nixclock.html#ready

I also bought a dozen XN3 clear glass nixie tubes for 50p each some time ago from I think J.N. Bull. (No idea what they cost these days). I then bought seven second-hand Mullard ZM1080 nixies at a radio rally for £1.00 the lot. I had in mind other projects such as nixie thermometers (one featured in Elektor), but often several components aren't easy to source so the projects got side-lined.

I built one nixie clock for myself in a plain grey ABS project box - nothing to look at, but a nice conversation piece! Later, I built one for my younger son in a rosewood box. A pic of the grey one is attached, together with a pic of my stock of nixies.

I've mentioned before that I've often fancied building a 'scope clock' which are also a nice conversation piece, if necessarily bulky. I have a 3BP 3" diam blue persistence scope tube, but it would take too much time that I don't have to build a clock, and wouldn't be cheap so it's another project destined never to materialise here at 'Bleak House'.

Mt first nixie tube project was in 1974 when I built a 200MHz frequency counter from a Radcom design. It's still going strong. I had to extend the 11 short leads on each of the five tubes, so that meant 110 soldered joints from the tubes to the veroboards on which they were mounted. A bit like sewing mailbags in prison! At the pic below the counter is displaying a 100mHz frequency from a Heathkit signal generator, alongside a pic of the nixie display boards inside the counter. The only mystery to me is how I found the time when I was so bust in mid career with a young family. Ah, that's it - mystery solved - no internet back then!

Hope that's of interest.

[pwdrive]

I remember the Dekatron.

Lawrence.

[Joe]

You have mentioned that clock before, David, so don't fear that you were having a 'Senior Moment.'

I must say I'm tempted as I've finally bought a new printer cartridge so can make PCBs.

Like you and the 'scope clock though, I don't need a clock and would have trouble finding somewhere to put it if I did make one.

- Joe

[Nick]

I have a couple of scope clocks built about 15 years ago - quite a lot of small crts in stock if anyone is after one for a clock. I'll get some photos out...

Some of the Russian nixes are only a few dollars each - the general rule is that the bigger the digits the rarer and more expensive the tube.

The biggest of the Russian nixies, the IN18s, are about USD 40 each now.

East German CD47s/GR114s are not only extremely rare and absolutely enormous, they now cost well over USD 1000 each.

Dekatrons predate nixies - they were quite slow - the fastest only counted at maybe 200khz and were hydrogen filled which invariably leaked resulting in most of the remaining fast tubes not working any more. I supplied a load of my dekatron stock to the Bletchley WITCH rebuild project.

Nixies basically died when LEDs appeared -LEDs didn't need HV and were easy to drive...

[pwdrive]

We had a Dekatron counter at tech when I was doing my C&G at tech, in the same room was a Heathkit analogue computer, can't remember the make of the Dekatron, it was back in the 60's.

Lawrence.

[Nick]

Details of the clock and PCB can be found here:

http://www.electricstuff.co.uk/nixclock.xxxx

I would most strongly recommend that no-one builds from that design. I know Mike Harrison - he's a good engineer - and even he says that its a dangerous design - he's gone to the length of adding all sorts of warnings to the page.

There are many far better and safer designs out there - if you just can't help yourself and must build the above design, use back-to-back transformers (mains:12VAC->12VAC:mains) to fully isolate the design.

Try something like Mike Moorrees design at http://threeneurons.wordpress.com/nixie-...-pendulum/ instead... (his whole site is a bundle of fun and full of good, solid, tried-and-tested, information & designs...)