Content originally posted in LPCWare by KaraMuraT on Thu Jul 15 11:18:37 MST 2010
I think this pull-up would not be sufficient, because I know that spikes and they won't go until you filter them.
It's because the spikes are so strong, affects your VCC down below the limits and for a long time. Maybe a couple of milliseconds.
I think the rooms lamp is an old style fluorescent, spikes are caused because of the starter. Choose a big capacitor according to your circuits power consumption like 2200 uF or so, solder it to the input (VCC to GND). And take a 1uF cap, solder it to RESET input.
I hope this can help you. The caps are life savers :)