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| Nixie Tube Multiplex Frequency and Blanking |
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| NivagSwerdna:
According to the multiplex section of... https://threeneurons.wordpress.com/nixie-power-supply/ ... When multiplexing there should be a blanking period between 100us and 300us between lighting elements and an on time somewhere between 1 and 4ms I have a nixie driver for six tubes that is driven as two sets of three tubes (via 2x HV5812) Currently I have a simple 100Hz interrupt which alternately lights one or the other set.... i.e. effective frame-rate of 50Hz. (I don't currently have any blanking period). This just meets the max frame time of 20ms criteria described in the linked page. It seems to work... I don't see artifacts as far as I am aware. I'm about to revamp my software to introduce some fade and scroll effects and thought I should revisit blanking. 100us to 300us would need my interrupt frequency to be somewhere between 3.33kHz and 10kHz. (At that sort of frequency I will have to pay closer attention to the timing of the Interrupt routine) My current ON time is 10ms for each set... I could make it 9.8ms blank for 0.2ms ... 9.8ms blank for 0.2s repeat or perhaps... 4.8ms blank for 0.2, 4.8ms blank for 0.2,... Or.. 9.9ms blank for 0.1,.... or 4.9ms blank for 0,1,... or 1.9ms blank for 0.1,.... Any comments? Are there any frequencies I should try and avoid that might cause audible artifacts/resonances? |
| NivagSwerdna:
FWIW... I think I am going to aim for a 6.4kHz Interrupt... If I have 1 period blanking and 19 period MuxA, then 1 period blanking and 19 period MuxB repeat... I get... 156us blanking, 3ms ON time. For an overall frame rate of 160 frames per second (i.e. 6.25ms frame rate) If I further divide that into 32 divisions of 5 frames I can have 32 divisions supporting PWM of 0, 20, 40, 60, 80, 100% Now to work out how to do the software! (Incidentally I do notice a bit of a buzz from the tubes even at 100Hz.... but is only audible when I am very close) |
| NivagSwerdna:
It seems I'm on my own with this one... :( I guess most people don't write multiplexing routines for nixie tubes anymore. With an interrupt rate of 6.4kHz.... I have 156us blank, 2.97ms Pattern A, 156us blank, 2.97ms Pattern B which I call a 'frame' Grouping into groups of five frames I change Pattern A and Pattern B to be ON for 0,1,2,3,4 or 5 frames to give a form of dimming. When fading up/down i.e. changing ON frames from 0/5, 1/5, 2/5, 3/5, 4/5 and 5/5 with a fade increment every 30 frames... I seem to get about the right effect, the flicker is quite noticeable when dimming up one cathode at the same time as dimming down another, when I dim up one and then fade out the other it seems better. I have a few effects coded now... scroll, slot machine, fade digits, scroll-back (when displaying '0' after '9', instead display 9876543210 in rapid succession). Does 6.4kHz sound reasonable for a 2-way multiplex? |
| niekproductions:
Hi, sorry for reviving your old topic. Did you ever get the nixies working at your 6.4kHz pattern? |
| NivagSwerdna:
--- Quote from: niekproductions on May 02, 2019, 05:20:47 pm ---Hi, sorry for reviving your old topic. Did you ever get the nixies working at your 6.4kHz pattern? --- End quote --- I got something working... and working very nicely... let me dig out what I did in the end...! |
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