I've built the 'beginners' lightning detector from techlib -
http://techlib.com/electronics/lightningnew.htm (first schematic shown), without any changes, using the sensitivity pot in place of the fixed resistor.
It works well, so far, (without any lightning for real testing), it reacts to a spark from a gasmatch, and my Jaycar jacobs ladder, and even if you pull a polarfleece jumper off within a couple of metres.....
I've strapped an arduino off the rear that watches for the low pulses, counts them and puts it on a webserver for monitoring - I don't have time to sit and watch for flashes!
The issue is - I have this outside in my observatory (away from home wiring/switches) and it is all quiet until the day warms up - then it starts to fire off fairly rhythmically, where I end up with 50-80 pulses every 5 minutes. On any given day, the number per 5 min seems quite stable as the temp plateaus, then as the afternoon cools off, settles back down again....
Winding back the sensitivity does help at a given temperature.
I'm keen to get to the bottom of this, even if only to advance my knowledge.....
Does anyone have any pearls as to where the issue might be? in the LC tank, transistors? I've read up on capacitors changing capacitance with temperature, so I've ordered some C0G ceramics in the hope this might help.
The circuit author recognises the circuit is temperamental in the heat at higher sensitivity, but didn't suggest why, and I've asked him so many questions lately, I thought I'd try this forum......
Thanks for any suggestions.....
Lee