All good comments.
I am going abit slow here, which is probably a good thing. I do not own a scope, and this is one of the few projects that I have needed one, so I am able to use my work scope for short checks. But it is slowing me down abit.
Assuming I will get the RCX/NXT interface done, I have been doing some thinking about my SW.
I agree on the Xstr addition. Been thinking I need to work on my charge/discharge time more though. I was going to try a R1 at 50 Ohms and R2 at 8 or 10K . Then I will add the Xstr and check output.
I am familiar with the "powered" sensor bridge and have spent some time on an IR sensor that is working well (now in Kickstarter!!); https://sourceforge.net/apps/phpbb/mindboards/viewtopic.php?f=2&t=1754
I am hoping to use this sensor as a passive (ie. touch sensor) instead of a powered sensor. So, after the pulse out xstr, I will have a 400Ohm (as measured on my old legacy touch switch) pull down. That should work, eh?
I still need to wire my 9V from my geiger kit to my RCX, and add in a 5V regulator for this circuit. But I was also thinking I could use an RCX output instead of a 5V reg, but the RCX outputs are at about 9V, right? SO, still not sure about the final interface. Will glance at the other sensors again, but looking at those before did not see any that get 5V from the RCX.