I dont recommend the IN-1; it's a low-quality tube. See my other postings about it.
You should think of nixie tubes as current-controlled devices; it requires a certain amount of current to produce the desired brightness. As with any device, you dont want to exceed the maximum recommended current, otherwise the device's lifetime will reduce. That said, it takes a certain voltage to initiate the glow (discharge), which is the ionization voltage. Before the onset of ionization, the current is very low. As the tube ionizes, the number of ionized gas atoms increases exponentially, and so does the current. If you were to allow the current to continue unabated, it would get very large and rapidly destroy the tube. An extreme example is a lightning-strike. By adding a properly sized series-resistor, as the current through the tube increases (a direct result of ionization), the voltage-drop across the resistor will increase, and the voltage across the tube will decrease (this assumes a constant supply voltage), which tends to reduce the current. An equilibrium is reached where the voltage across the tube is sufficient to keep it illuminated. Be aware the voltage-drop across the nixie tube while it's illuminated will vary from tube-to-tube, and also during it's lifetime. Also be aware that a small change in voltage will result in a large change in current, therefore you really cant rely on a constant-voltage across the tube. Now, you can take the design of a nixie-tube driver one step further, and make a constant-current driver, which is what I did on my big clock. I wont go into details here. The easiest way to create the roughly 170 volts to ionize a nixie is to rectify+filter the 120V AC line. However, as the tube ages it's ionization voltage might increase above this and your tube will no longer illuminate. So, you can run at a higher voltage; on my first nixie clock I used a voltage-doubler to create +340VDC, then used a larger series-resistor. In this case, I used an 82K resistor to drive a Burroughs 5092 nixie at the optimum 2.2mA. The IN-1 runs about 3mA so you would use a lower resistor around 70K. Running at 340V does not harm the tube, but it does waste more energy in the form of heat dissipated by the series resistor. Another option is to use a "boost" transformer; I did this on my big clock to produce +210V. This gives me plenty of margin for the ionization voltage without wasting as much energy as a 340V supply. With 15 tubes, there is a noticeable savings in energy running at 210V vs 340V. -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/9f661ba9-2757-4ffe-868e-cc52df995bd0%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
