Hi,

One my friend asked me to write a program which controls some input signals provided with piezo sensors. He uses self-made piezo sensors extracted from a cigarette lighter.
The problem I have stuck up, is that my program hangs/resets time to time when input signal comes.

I think that this is because these piezo generate very high voltage. Am I right? But I cannot understand how they influence on MCU: via signal line or through power/ground. And I doubt that internal watchdog of MCU may help me somehow because it seems that oscillations stop completely due MCU hangs (as for now I use AT89S53).

Here is the input schematic. Maybe somebody has ideas/improvement how to keep stability of work?



Thanks,
Oleg