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|Giant nixie clock|
|Written by Hans Summers|
|Saturday, 28 March 2009 08:49|
At the beginning of 2001 I had never heard of nixie tubes. Then I came across Mike's Electric Stuff and saw his Nixie Clock. Almost instantly I fell in love with nixies... then I had the idea of building a nixie clock and this project was the result.
Z568M Nixie Tubes
After some searching on the web I found the nixie tube I wanted. The tube is a type Z568M, that had been manufactured in East Germany. I purchased a set of six from Jan Wuestens. The "New Old Stock" tubes arrived in England in their original cardboard boxes, and plenty of padding and packaging to keep them safe during the journey (well done Jan).
I used a very similar circuit to Mike's nixie clock. Mine is a 6-digit clock, i.e. has an extra pair of nixies for the seconds. I made a few very minor modifications to Mike's circuit. I moved the seconds hold switch to earlier in the counter chain, because I found that otherwise a full second did not elapse between letting go of the switch and the seconds being incremented. Since my clock display seconds, I also connected the colon nixies to be on continuously. I omitted any form of mains isolation, in the interests of living dangerously (do this at your own risk!). I found a series resistance of 22K to be about right for the Z568M, but they overheated so I replaced them with two 47K resistors in parallel (23.5K). The total cost of the electronic parts for this circuit (excluding the nixies) was under UK £10. Of course, the nixies are very expensive, and the materials for the cabinet.
I did not use a printed circuit board (PCB), instead I used my favourite method of construction, which is plain matrix board and wire connections. The circuit is built on three circuit boards. The first holds the rectifier, divide by 50 circuit, seconds counters and seconds driver transistors. The second and third boards hold the counters and drivers for the minutes and hours digit pairs.
If you have java enabled on your browser, you will have seen a working simulation of this nixie clock at the top of this page. This uses an excellent java applet called DJClock by Naeem Malik, of Xanasoft. Note: A mouse click on the clock suspends the time, another mouse click will restart it. The digits template for this clock is shown below. This picture was obtained by laboriously photographing the clock from the same position, with different displayed times until I had all the digits 0 to 9. Cut and pasting in an image editor resulted in the template. The embedded comments line is 11:0:84:169:254:339:424:509:594:679:764:849:885
This image is used as the background:
Mike Hungerford did a great job of cleaning up both the digits and background images and kindly sent me his improved files, which you now see here. Thanks Mike! Feel free to take these digits and use them on your own java clock, subject to Naeem's copyright and conditions of course.
The following articles about Nixie clocks appeared in the January and March editions of Radcom, the journal of the Radio Society of Great Britain (RSGB). The March article mentions and pictures my giant Nixie clock. The images are black and white which keeps the download time down but means the photographs aren't reproduced very well.
A 12-inch (30 cm) ruler is shown in front of one of the photos so that you can see this is quite a sizeable clock. In that photo, the seconds digit increased from 3 to 4 during the exposure of the camera, which is why you see a 3 and 4 superimposed. The glass front panel is bevelled. Glass panels were cut to specification from a local glass shop and glued together with a silicone adhesive/sealer intended for aquarium applications. The small "pills" fixed to the backplate anode of the nixies are "getters", containing a small amount of a material such as barium, which sucks up any residual oxygen in the tube. The feet of the clock base are made from shaped pine strips, with a picture-frame type profile. Red felt is fixed to the bottom of the feet and two self-tapping screws store a bar magnet in place for setting the time.
The seconds nixies were unscrewed for this photograph which shows the soldered connections to the nixie pins. The resistors are 22K, but you can see they are blackened due to overheating. I later replaced each 22K resistor with 2 47K resistors in parallel. The pair of nixies on their board are screwed to the pine base using 4 self-tapping brass screws.
Left: View along the nixies, taken from the seconds end. This shows the depth effect of the different nixie digits, due to their different depth placing in the digit stack.
Middle: A close-up photograph of one of the rightermost nixie showing the number 5. Note the dust on the nixie! This picture shows the internal structure of the Z568M quite well.
Right: Nixie Close-up from above, again showing off the internal structures of the Z568M Nixie.
FAME at last!
Nixie clock by Jonathan Kelly MW3KGQ
|Last Updated on Sunday, 17 April 2011 02:41|