Interesting. Anodes and cathodes are biased to 80V. Also, note that the segment drivers use current-limiting (emitter resistors).
On Tuesday, May 25, 2021 at 8:48:50 PM UTC-7 Richard Scales wrote: > OK, I think I'm homing in on a solution. > > Assuming that I go with HV513 for high and low sides with the VPP's set > accordingly there is then the whole series resistor thing to work out as I > believe that peak currents can be higher in a multiplexed situation (did I > read that right?). The circuit that I have seen for the Bally Pinball > displays appear to be using a total of 1k5+1k2=2k7 though I have no > knowledge of the specification of the displays that they were using. > > For the ZM1500 displays I have here - the specification suggests anode > current between 0.4mA and 1.0mA with a maintaining voltage of 125V > (assuming that I translated that correctly). > > Assuming a current of 0.5mA and a supply of 170V that suggests a series > resistor of (170-125)/0.5 K = 90K, a world apart from the values that > Bally are suggesting but I don't know their displays characteristics. > > Is there a suggestion that, depending on the 'on' time of the segment, the > actual current could be set higher? > > The same specification also lists an anode peak current of 10mA. > > For now I'll plan to use something like 90K on each cathode to see how > that goes - unless anyone can suggest that is hideously wrong? > > - Richard > > [image: Bally.JPG][image: ZM1500.JPG] > > On Tuesday, 25 May 2021 at 20:11:18 UTC+1 Paul Andrews wrote: > >> The HV513 is push/pull. You can use it for the anodes and the cathodes. >> You set Vpp to 170V for the HV513 you are using to control the anodes. You >> set Vpp to 80V for the HV513 you are using to control the cathodes. Each >> pin can source or sink 20mA. You could even chain them all together, as far >> as the SPI interface is concerned. >> >> You could use a resistor divider for the 80V, or you could use a zener >> voltage clamp. There should be next to no current flowing when the cathodes >> are at 80V (otherwise they would be lit). >> >> On Tuesday, May 25, 2021 at 1:25:44 AM UTC-4 Richard Scales wrote: >> >>> I think I am getting a little closer to understanding this all a little >>> bit more. I have almost grasped the concept of clamping the cathodes at an >>> intermediate voltage to aid switching them on and off in a timely manner in >>> an effort to minimise ghosting. >>> >>> Now it's all down to driver choice and chip count. >>> >>> How about HV5812's? i have seen these used in multiplexing circuits - >>> especially those where a group of say 6 nixies are split into two groups >>> then the 20 bits from the driver are split into two groups of 10 bits, >>> each group for one set of three nixies. that works just fine for nixies, >>> not so good for a 16 digit device with cathodes common to all! >>> >>> Regardless, it would be slightly more efficient than using a 32 bit >>> device though ultimately an 8 bit device would suffice. Using the HV5812 I >>> can see that I can just connect Vpp to 80V, job done. If I wanted to use >>> HV513 (on the grounds that I only need 8 bits) would I then just clamp each >>> cathode to 80V via a suitable resistor? >>> >>> I guess I could simply not worry about it and waste the bits, I'm only >>> ever going to do this once or twice and one of my design goals is to make >>> this thing as small as possible. >>> >>> For the high side i definitely need to switch 16 anodes so I need to >>> employ a push/pull device - HV5523 will do that or I could perhaps use a >>> couple of HV513's - again, the easiest thing to do would be to use a single >>> HV5523 and waste half of the bits. >>> >>> In an effort to home in on a solution - a single HV5523 for the 16 >>> anodes and a single HV5812 for the cathodes (clamped to 80V) - have I >>> missed anything crucial here? >>> >>> I just feel that I should get a handle on this multiplexing thing. I now >>> have a couple of different multi digit panaplex displays coming so I need >>> to come up with a plan. >>> >>> I have some ZM1500 (12 digits) on hand and some IGP-17 (16 digits) on >>> their way. >>> >>> ... and I've not even started to think about the timing of all the >>> various switching operations yet! >>> >>> Thank you all for helping me with my education >>> >>> - Richard >>> >>> On Friday, 21 May 2021 at 19:13:35 UTC+1 nixiebunny wrote: >>> >>>> Richard, >>>> A single push-pull HV driver chip will not be able to drive a >>>> multiplexed display. >>>> >>>> The reason is that it only connects each tube element to either 0V or >>>> 180V. It is not capable of leaving an element disconnected. >>>> >>>> >>>> On Thu, May 20, 2021, 8:45 PM Richard Scales <[email protected]> >>>> wrote: >>>> >>>>> Sorry, I mean using the same type of device to control the anodes AND >>>>> the cathodes but but the actual same piece. >>>>> So, using an HV5523 (or perhaps multiple HV513, multiple because there >>>>> are probably 8 cathodes (seven segment panaplex displays) and 16 Anodes >>>>> (16 >>>>> digits)) could be a way forward then. >>>>> Please could you let me know more about the need to clamp the cathodes >>>>> to a certain voltage? (Exposing my real lack of understanding here!) >>>>> - 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]. 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