It sounds like you like to try something new rather than using the old MPSA transistors. Tell you what, why don't you use an opto triac? For example the FOD4208, for sure it can support the required LED current. The only thing that will be a (small) challenge is to switch it off as it won't do that for as long as the current flows to the triac, which means it will stay on until you pull the plug..... You will need to disable all segment drivers so that the current will become 0mA, and then the triac will turn off and you can then go to the next tube. You need a blanking time anyways, so it's not really a disadvantage to do it this way.
There's probably people who have tried this already, so you may ask them if that works fine, but I don't see any reason why it shouldn't work. Michel On Aug 23, 5:47 am, Matthew <[email protected]> wrote: > Finally getting back to this after more boring bits of life, and finishing > a couple of nixie clocks I was working on. Back to FLW = Back to asking > questions - this time about resistor values. > > * As before, I'm experimenting with cathode drivers - and came across this > blog > post<http://lucsmall.com/2011/07/19/using-the-sn75468-as-a-nixie-tube-driver/>which > explains it (via some help from this group). I also tried it with the > 50v ULN2003A and a 47v Zener diode and it works - this is good news since > they are cheaper and more readily available. I'm not quite sure how to > calculate the pullup resistor, but it doesn't seem too critical. > > * However, given that I know from the spec sheets what current should be > going through each cathode, I can't quite get my head around what voltage > differential I should be using to calculate the cathode resistors...? > > * Similarly, I just discovered that unlike LEDs, nixie circuits seem to use > an anode resistor as well as cathode resistors - why is this? The spec > sheets of the tubes show the anode current - but as above, I'm not sure > what voltage difference I should be using to calculate this. > > * Also been experimenting with anode drivers; I was going to use an > optoisolator, but I'm trying to make a design which will drive both the > nixies and LEDs (with appropriate changes in supply voltage and resistors), > and it turns out I can't get one to handle the current of the LEDs. So I'm > probably back to the common MPSA92/42 combination. I see lots of schematics > including these, but I'm not quite getting the logic of how the resistors > are calculated... > > As ever, any insight hugely appreciated... -- 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 https://groups.google.com/groups/opt_out.
