Direct drive or multiplexing - I would vote for direct drive. It is just simpler to control, as you need to set the GPIOs only once a second. As far as I 've heard, controlling GPIO of a RPI is problematic, so you could use shift registers or I2C I/O expanders. With those you aren't really limited when it comes to amount of pins used. The main advantage of multiplexing is less pins needed to control the tubes. With 6 tubes you need at least 60 outputs for direct drive and only 16 for multiplexing. Also, I do not know if RPI has timers working in same way as they work on standard microcontrollers, and executing the multiplexing routine is critical for non-flickering display. Both displays can achieve same brightness. In real designs, multiplexed displays used higher current per tube to achieve an average current similar to direct driven tube. Most hobbyists tend to use lower currents in hope of increasing lifespan of a tube, however I'd advise to stay over the minimum current, if it is provided in the datasheet.
Power supply - the problems with IN-18 and infamous blue spots do not come from the power supply voltage itself. 180V is perfectly fine as long as you use decend high voltage cathode switchers (Supertex HV shift registers, MMBTA42s or other 200+V transistors). *Stay away from 74141 *or their soviet counterpart. These devices are poorly constructed, consume alot of power compared to modern ICs and are old - no one guarantees that they will work after so many years. Poor transistor technology from these years is the reason why people are having troubles with blue spots. I do not know how the voltage can decrease life of the tube - you still need a current limiting resistor. Tubes die faster from incorrect current (peak and average). RPI doesn't have its own analog to digital converter. This means you cannot directly check the voltage at the output without an external ADC. I suggest using a standalone power supply unit, preferably with an Enable pin, so you could make some power saving routines. Other big nixies - within similar price range, Z566M/Z5660M. Very beauftiful, with thin and sharp digits. Durable, with long life time. Still avaible on the market in reasonable amounts, so getting a spare tube shouldn't be a big problem*. Datasheet has clear information about minimum average current, maximum average current and peak current per cathode. It also uses a more popular socket. *of course, no tube will be ever as avaible as russian tubes - Soviets produced alot more than needed ;) BTW. I've started my journey with ESP8266 very recently and I'm a newbie to the NTP topic. How often can I check the time at a server to be not considered a spammer? Is once per hour okay? -- 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/8767f505-e669-4ad7-8202-0cbb289ff547%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
