I'm glad your tube is working. It's unfortunate your driver got fried, but that is a risk when using a supply-voltage significantly higher than the max-rated voltage of the driver. The reasoning behind using the lower-rated driver is that the nixie tube will provide a voltage drop around 130-150 volts, so a 170V supply *should* only result in 40 volts at the driver. That's only true under ideal conditions. In reality, hot-swapping a nixie tube will momentarily expose the driver to the entire HV supply voltage while the nixie tube's parasitic capacitance charges-up (I've measured a few tubes around 10pF). I'm sure there are other scenarios that expose the driver to unsafe voltages.
If you cant change your driver, you may consider placing a bleeder resistor from each cathode (ie, driver output), to GND to shunt any pre-ionization current. You will want to use the *smallest* resistance that doesn't cause any cathode-glowing, which means it will be several megohms. This wont eliminate the risk of zapping, but it should reduce it. The only way to eliminate the risk is to clamp the driver pins to the maximum-allowable voltage of the K155. That would require a diode+resistor on every driver pin to a clamp voltage, which could be a shared zener diode. At that point, for size and cost reasons you would use a different driver. BTW, even a higher-voltage driver such as the HV5530 has some risks because there probably isn't full ESD protection on the output pins, therefore you have to rely on the offchip circuitry (which likely includes the nixie tube) for protection. As long as the driver is rated higher than the maximum possible voltage on your HV supply, there aren't any operational risks even if you swap tubes while your clock is running. -- 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/a3584b91-ffd7-4ed8-97b0-1c9aac4628c4%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
