adequate pull-down resistor value

[r0nd0m]

Hi there guys Im new here... Im from Brazil so Im sorry if you guys cant understand my poor english :P

I did some guessing job when finding the components value in this circuit, and I was already expectating some issues.. but Im really noob with electronics and I cant find a way for solving this. Heres my circuit in PDF format:



Its very simple.. you can see 8 lamps that will blink in a frequency given by the PIC. My big problem is when they are NOT blinking... When I turn of my circuit using that switch but keep it connected to the power source (an ATX PC power source) some of the lamps blinks weakly from time to time... its really annoying :P So I realised that transistors were receiving so much ESD for being darlington ones, that made me add that resistor (R12) wich one should grant 0V at the transistors bases..

Sadly there still one lamp that keep blinking..
My question is: How to find the resistor value that I shall use on R12?!! I think that a bigger value would make all the lamps to light again when source turned off, cause there will be no more "grounding" enough to "ground" the transistor base. And I think a lower value would reduce the lamps lighting when source turned off, cause there will be a easier way for the current flow... So whats the corret value?!?!


Its a shame cause its a very simple circuit.. Can you guys please help me solving it??

Plz! Thank you.




*EDIT: Guys, I noticed that my circuit generates some ESD that my television can feel... how can I solve it? I think those ISO especifications will be my next class topic... but can you guys teach me anything about preventing from being a source or a victim of ESD?! Thanks again!