RCX/NXT Geiger Counter (Ongoing)

[HaWe]

ah, ok - that makes me feel reassured

[circuitmage]

Ok, so now moving this onto the NXT. A few things to note;

1) I had NO problems with the RCX set-up as described above. Obvious limitations on the RCX (display, memory) had me move onto NXT now.

2) I modified the Electronics Goldmine kit (even the newer one has the same circuit as this link) per the following information;
http://www.eetimes.com/document.asp?doc_id=1278798 using the HV cap off the diode, the current limiting R on the LED. I tried the other changes but did not notice any affect on my board. Also, on my board, I cut the EG board size almost in half to get rid of abunch of wasted space.

While getting these changes up and running, noticed some things you want to be careful of;
* Using HV scope probe, I blew two boards transistors to the speaker. I suspect the probe caps got charged and discharged while probing. Replacing the transistors and the speakers work again. BE VERY CAREFUL when probing HV...not just for yourself, but for your circuit.
* Had an issue with a PS while connecting board. Suspect the HV noise on the GC board caused this. Which leads me to my 3rd point...

3) I suggest either filtering out well, or isolating the GC board power (ie GND line) completely from the controller you are using. I see lots of HV noise on the GC ground line, and do not want to risk damaging my NXT. Again, the RCX had no problem sharing a single supply.

4) I switched tubes and am getting very good results, but have one issue with a declining pulse output. After this issue is solved I will be good to go with the NXT.

Pictures and more details coming soon.