I’ve been putting nixie tubes in projects for a while now, following Nick de Smiths’s design found here. A really great write-up and explanation of how to make your own DC-DC converter for nixie tubes. The most important thing I’ve learned is that LAYOUT IS CRUCIAL. He emphasizes that in his write-up and you should really listen. (I tried otherwise once and failed miserably.) So the following is some results I got that I think would be useful to anyone considering building one into a project.
One reason I wanted to do this was that I noticed a while ago that with Nick’s design, the input voltage could be as low as around 5V and you could still get 180V out. However, once you put a load on it that may not be the case, so I wanted to see at a few voltages what kind of load could be supported, and what the efficiency was. Another thing to not was that I use slightly different parts than Nick, which I thought might improve my results. However, I was somewhat surprised that I couldn’t get as good of results as Nick did, although my layout was slightly different which I think may be responsible.
The graph below shows the efficiency of the converter vs. load current, for 12V, 9V, and 6V input. The excel file of all the data is at the end if your interested.
Originally I had planned on making these measurements at work using a setup that’s already there with an electronic load. That allows for taking hundreds more data points as well as varying the input voltage more. Unfortunately, the electronic load was only rated to 60V, and rather than risking the obvious, I figured I could just do it all by hand at home with a decade box. The decade box is pretty old but still functions fine, except for the 1 ohm knob seems to be dead. Originally I had set this up using a 25k pot I had lying around. However, if you put 180V across that, the pot has to absorb ~ 1.3 watts, and that’s at 7mA. When you get to about 25mA, you’re at 4.5 watts and so on…. problem is, most 25k, 10k pots are really only rated around 1/4 to 1/2 watts. So, it melted. On to the decade box, here’s some more pictures of the setup and the decade box.