I built Mr. Forbes clock and it is still working!
~ *mcvei...@gmail.com <mcvei...@gmail.com>* On Thu, May 20, 2021 at 9:45 PM Paul Andrews <judge2...@gmail.com> wrote: > It might work if you use two for the anodes with Vpp set to 170V, and one > for the cathodes with Vpp set to 75V. > > The need to force things to a specific voltage is to make sure the > transitions are fast to prevent ghosting or to prevent the off digits from > glowing. When you move the power from the first anode to the next you will > have to add a delay before you set the cathode states in order for the > anode current in the first tube to drop to zero below the sustain voltage, > otherwise the same cathode will light up in both tubes. Forcing the anode > to ground means that delay can be smaller. Conversely, if the off cathodes > aren’t clamped, it will take more time for them to rise from zero, which > would cause the next tube to display the same digit as the first tube when > you apply power to the anode. > > At least, that has been my experience. > > On May 20, 2021, at 11:45 PM, Richard Scales <rich...@scalesweb.co.uk> > 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 > > > On Thursday, 20 May 2021 at 19:37:57 UTC+1 Paul Andrews wrote: > >> I used a HV5523 to drive both - it is open drain. It worked fine, but I >> needed to clamp the cathodes to around 75V. The thing about a push-pull >> driver is that the push part is to clamp the cathodes, so whatever you are >> driving it will switch them between 0v and the voltage you want to clamp >> the cathodes at (e.g. 75V), so you couldn't use the same chip to directly >> clamp the cathodes and the control the anodes. At best you could use it >> control the PNP high side transistor. >> >> On Thursday, May 20, 2021 at 11:55:26 AM UTC-4 Richard Scales wrote: >> >>> Thank you for that - I was looking at the HV513 which is push-pull and >>> is rated for the higher voltage levels. >>> >>> Being push pull - can I use those for the High side AND the low side? >>> >>> - Richard >>> >>> >>> On Thursday, 20 May 2021 at 16:02:47 UTC+1 Paul Andrews wrote: >>> >>>> The HV5622 has open drain outputs, so the cathodes will be left to >>>> gradually float to whatever value they feel like. They probably won't do >>>> this fast enough to prevent ghosting and you don't really want them to >>>> float in a multiplexed clock anyway. I would suggest a push-pull chip for >>>> the cathodes, like the HV9808. >>>> >>>> On Thursday, May 20, 2021 at 1:06:54 AM UTC-4 gregebert wrote: >>>> >>>>> For my current clock project, I have a 9-segment / 13-character >>>>> display that must be multiplexed, so I use a 4:16 decoder to drive PMOS >>>>> anode-transistors on the high-side. The 4 bits into the DeMUX are piped >>>>> thru digital isolators (SI8710), and driven from the FPGA. I use an >>>>> isolated DCDC converter to provide a negative 12V supply relative to the >>>>> anode supply (about 200V, because it's unregulated). >>>>> >>>>> The low-side for the cathodes are just NPN current-limiters, also >>>>> driven by the FPGA. >>>>> >>>>> >>>>> [image: ScreenHunter_32 May. 19 22.00.jpg] >>>>> On Wednesday, May 19, 2021 at 9:21:49 PM UTC-7 Richard Scales wrote: >>>>> >>>>>> I am trying to learn about multiplexed displays (I thought it was >>>>>> about time I had a go at this) and I believe that I understand the >>>>>> basics >>>>>> - in as much as it requires the switching of the required anode as well >>>>>> as >>>>>> the required cathode (all of which are wired in parallel). >>>>>> >>>>>> I understand that I can use something as simple as a single >>>>>> transistor for the cathode (low side) and a couple of transistors for the >>>>>> anode (high side). >>>>>> >>>>>> Again, for the low side driver I could use any of the 'standard' >>>>>> shift register type drivers that we use in clocks such as an HV5622 (I >>>>>> appreciate that's way too many bits and I'm sure that there will be a >>>>>> smaller equivalent part available. >>>>>> >>>>>> Specifically - is there such a part that I could use for the high >>>>>> side, ie switching the HV to the relevant anode? >>>>>> >>>>>> I know that I could use a simple shift register (74595 for example) >>>>>> plus the transistors for a high side switch, I just wonder if there is a >>>>>> part which does all that in one package? >>>>>> >>>>>> All pointers gleefully received. >>>>>> >>>>>> - Richard >>>>>> >>>>>> >>>>>> -- > You received this message because you are subscribed to a topic in the > Google Groups "neonixie-l" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/neonixie-l/XWjWh-epHQc/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > neonixie-l+unsubscr...@googlegroups.com. > To view this discussion on the web, visit > https://groups.google.com/d/msgid/neonixie-l/edd2d9c8-bf41-43cf-af3b-546041d3fb0cn%40googlegroups.com > <https://groups.google.com/d/msgid/neonixie-l/edd2d9c8-bf41-43cf-af3b-546041d3fb0cn%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > -- > 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 neonixie-l+unsubscr...@googlegroups.com. > To view this discussion on the web, visit > https://groups.google.com/d/msgid/neonixie-l/7DEFE1A4-8DD8-460F-A023-4773641B6815%40gmail.com > <https://groups.google.com/d/msgid/neonixie-l/7DEFE1A4-8DD8-460F-A023-4773641B6815%40gmail.com?utm_medium=email&utm_source=footer> > . > -- 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 neonixie-l+unsubscr...@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/CAKYv7NTg2T8kyenuUFjeinuZSsxzDMM%2BhzYP6GFG5MLk8OAfCw%40mail.gmail.com.
