User Manual IN16-4-V1 Nixie Clock 
Power for your Nixie Clock 
The clock does not include a wall adapter. You should get a universal adapter yourself, these 
are not very expensive. The preferred voltage is 12VDC, but often 9VDC – 15VDC will do 
nicely too. The middle pin of the plug is the positive. Universal adapters often come with a set 
of various plugs, choose one that fits. If none them fits, you can use the dc-plug is included 
with the clock. If the clock does not work, you may have gotten the polarity wrong. Change 
the polarity and try again. 
Setting the Nixie Clock 
Turn on the clock by plugging in the wall adapter. The time will start at 12:00 and blinks. 
Press and hold the set button, for about 5-6 seconds until the first tube will turn on its decimal 
point. Release the button. 
Now, with each short press of the button, you can advance the first digit. The format is 24 
hours, so the first tube only changes from 0-1-2 etcetera. After the digit is set correct, press 
the button again for 2 seconds, and see that the second tube will turn on its decimal point. Set 
all the other tubes in the same way. 
Once you have set all digits, press and hold the button for 5-6 seconds, and the clock will 
resume normal operation. Note that the internal timpekeeping of seconds will be reset to zero. 
To set your clock as accurately as possible, press and hold the button exactly when your 
reference clock changes to the next minute. The 5-6 seconds you need to hold don’t affect 
this, the software compensates for that. 
At first, this may seem a bit of a hassle, but after a while you will notice that it is remarkably 
easy to set the clock. 
Calibrating the Nixie Clock 
The clock comes calibrated. There’s a label on the bottom with the correct calibration value 
for use at normal room temperature. If you use the clock in extreme cold or warm places, you 
may want to recalibrate it. Press and hold the set button, for about 7-8 seconds. While you 
hold it, you will first see that the first tube turns on its decimal point, and then the second tube 
will turn on its decimal point. Now release the button. There should be 4 digits displayed now. 
Here you can set a new calibration value for the timing of the clock. First set this value at 
5000. After setting this value, press and hold the button for 5-6 seconds, to return to normal 
mode. This value will be stored inside the microcontroller. Turn off the clock, and turn it on 
again. 
Now set the clock, using a reliable time reference. Set the clock as described earlier, and wait 
until your time reference matches the time you have set. Now press and hold the set button for 
5-6 seconds, and notice that the clock now runs synchronous with your reference, both 
displaying the same time. 
Using the standard calibration value of 5000, the clock should run with a better accuracy than 
+/- 10 seconds per day. Let the clock run for a couple of days, and note the time difference