| Well, I was thinking that a capacitor between the nixie's | anode and ground (especially a big one like 33uf) is going | to make that waveform more DC-like.
Er, NO ! The purpose of multiplexing is NOT (like in NO) to meter out the power. Its ALL (like in everything) about TIMING (like everything at EXACTLY the right time) ! The whole point about putting a switch on the anode is so that, and only that, tube is ON when the data is presented to its cathode(s). REMEMBER, ALL CATHODES, of ALL TUBES, are bussed together, in multiplexing. All the K0's are tied together, all the K1's are tied together. Only ONE (1xN multiplexing example) tube can be ON at any one time. If you put a cap in the anode circuit, then it will several tubes will be ON when the cathodes are switched to present another tubes data. Ghosting will be a CERTAINTY. In fact, that's why there is a resistor across the base and emitter of the high side PNP (MPSA92). AND we tell (INSIST) on people not trying to "Muntz" it out (wiki it). Its needed to make the transistor switch OFF faster. To make sure you don't have ghosting: (1) Add or keep a 4.7K to 22K resistor across the base-emitter junction, of the anode switch (PNP, MPSA92). If its missing, the transistor (due to charge across the BE junction; not linear) will be enough so it will still be ON (for a short while) when the next tubes cathode data is presented (at the cathode). (2) Add blanking intervals between digits. Nominally, ~2X-5X the tube's normal response time. Nixies take ~50uS to turn ON, so a blanking interval between 100 to 250uS, is recommended. During blanking, turn ALL anodes OFF. This is better than turning all cathodes OFF. Why ? If you are using a 74141 (or similar) to drive the cathodes, if all are off, the voltage at the cathodes, WILL exceed the zener clamps, and current WILL flow. It will show on several cathodes, and will look like an orange blur. Always keep at least ONE cathode ON. Somewhere during that blanking interval, switch the ON cathode from the value of the last digit, to the next one. I've experienced all of the above first hand. All of it has been confirmed by further scope images. As always, Don't believe me. Try it out for yourself, both ways. <mini-RANT>The essence of modern science, is not the body of knowledge that it has acquired, but HOW that knowledge was acquired. By experiment - TRY IT OUT - DO</mini-RANT> -- 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.
