On Feb 28, 12:14 am, Sixsmith <[email protected]> wrote: > Hi, > We're experimenting with making our own nixie tubes in our shop. I was > planning on making the cathode out of stainless steel, but was > wondering if anyone had any advice about the best material to use. > Would it be better to try to find something rare-earth coated, or > isn't it necessary?
Weston (pp334) says that nickel is ideal but not strong enough, and recommends nickel-iron alloys or stainless steel. He recommends a h:w ration of 2:1 for side-view tubes where the cathodes are close together and 1:1.6 (is that a misprint - does he mean 1.6:1 ?) for end- view tubes where the cathodes can be further apart. Note that sputtering increases markedly with decreasing pressure, so you need the highest pressure you can in your Penning mixture such that you get reliable striking. If you introduce Hg to reduce the sputtering, use only a tiny amount as too much will deposit on the inside of the tube and reduce visibility. In the various books I;ve read, life of non-Hg doped tubes is generally rated at between 1000 & 1500 hours - with Hg doping this can be many 10s of 1000s of hours and indeed over 100,000 (allegedly!) in some cases. With only 0.2W dissipation, the actual cathode temperature can be a few hundred degrees C, so the cathodes mustn't be stacked too close as they can distort in use. The recommended minimum spacing is 0.6mm which allows a stack depth of 0.7mm per layer, i.e. using 0.1mm sheet metal. Glyphs are either stamped or etched from the sheet. Design of glyphs is quite cute - many tubes rely on the width of the stroke changing to try to ensure that each digit has approximately the same surface area so with a given anode current they have similar brightness. The anode is non critical as long as its pretty evenly spaced - the front mesh is as transparent as possible, and the back plate is coated matt black to reduce reflections. Note that some tubes have no anode! They rely on making unused cathodes into anodes - a neat trick gaining great aesthetics & visibility at the expense of requiring extra electronics. I would get an assortment of dead tubes and have the metal analysed - watch out for the mercury in long-life tubes. Also look closely at the exact dimensions of each glyph - many larger tubes actually specify different anode currents for different glyphs (or segments, e.g. in the B7971). Cheers Nick -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/neonixie-l?hl=en-GB.
