Nixie thermometer – smoke test

by luca
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The design and development of this project is described in ten blog posts: for the chronological list follow this link

After having sourced all the components needed to build my thermometer, the first thing to do is to perform a smoke test, that is a test to verify that all the components work as expected.

Specially if you’re working with power supplies, it’s indeed very important not to trust them: a mistake during the assembly, a component with a wrong value can cause your module to output a voltage ten times higher than the nominal value, destroying the precious components it should power!

I therefore powered with a regulated 12V the supply module and connected my multimeter to the HV (high voltage) output for measuring the real voltage. I also changed the value of the potentiometer that regulates the output voltage, checking that its range was what has been specified in the datasheet:

nixie-6 nixie-7

After having tested the power supply, I could test each nixie tube. A nixie tube has a PIN (anode) connected to the positive high voltage and different PINs (one for each digit/symbol that can be displayed) that must be connected to the ground to turn the digit on.

It’s very important to use a resistor (in my test with a value of 10Kohm) in series with the tube to limit the forward current:

nixie-8 nixie-13

All the nixies worked, so I soldered them to the sockets. IN-14 nixies have two digital dots (one on the right and one on the left), while the sockets have only 12 pads: it was necessary to remove a dot’s terminal (I didn’t plan to use it anyway).

nixie-9 nixie-10

In the end, I soldered the female strips to the sokets:

nixie-11 nixie-12


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