I acquired a bunch of Itron FG2013A1 VFD displays. These are 16 segments (plus DP/comma) 20 character displays.
I wanted to use them as a reason to try and grasp the nettle of multiplexing (which has eluded me for some time). I hooked the filament up to 4.5V and applied 12V to a grid and 12V to some segments - all good so far. I had a bunch of HV5812 to hand and tried driving the display with these to turn on grids and segments - still good. I made up a board with 2 x HV5812 drivers cascaded to give me a total of 18 segment drives and 20 grid drives. All I had to do then was to crack the multiplexing thing. After some time and with assistance I got an interrupt routine firing every 1mS which would set the segments and grid I wanted to turn on and an SPI.transfer later - the display showed what I wanted. 1mS x 20 characters gives a refresh of 50Hz (if my math is right) which looks just fine. .. however, when I want to show all 20 characters (in my test case 0-9 twice) I see some 'interesting' results. The A/C filament drive is connected at the left hand end of filament, the other end to GND. I am using 12V for VPP to the HV5812 drivers so I expect this to be what is going to each grid and segment that I want to activate. The ISR just sets the segments for the current grid and turns them on in one hit (the SPI.Transfer is sending 40 bits - 20 for the grids, 18 for the segments and two are wasted) Everything checks out using a logic analyser and there is plenty of time left to do other stuff - I am using an ESP-32 from AZ_Delivery for the testing and am using a CD40109 to convert the 3V3 logic to 5V. I can see that it really is showing the right segments on each digit - it's just that there is a whole bunch more illumination of other unwanted segments which is far worse at the A/C supply end of the filament and completely gone ant the GND end. I call upon those more experienced in these things to see if anyone can point me in the right direction? I plan to try a DC filament drive next just to rule that out. - Richard -- 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 view this discussion, visit https://groups.google.com/d/msgid/neonixie-l/2cbe9562-52ab-4bdf-833e-2d5343d05228n%40googlegroups.com.
