CollinK
Newbie level 1
I have a circuit that is essentially a shock alarm. It uses a piezo shock sensor. The main circuit is based around an LM555 chip such that the shock sensor triggers the LM555 which drives a transistor which drives a horn. The 555 chip is being used in the standard monostable configuration. The circuit works properly except that when it is first powered up the shock sensor will register a false shock and the alarm will go off. Thereafter it all works correctly. Every fresh power on presents this problem.
I'd like to somehow prevent the 555 from registering the false trigger pulse upon start up but everything I've tried has not worked. I've tried various schemes with capacitors and resistors to try to keep reset low or prevent the trigger from showing, but I'm just not hitting upon the right steps to do this. Admittedly I'm somewhat new to electronics. Does anyone have any tips as to how to prevent the initial start up weirdness from triggering the alarm? Thanks!
I'd like to somehow prevent the 555 from registering the false trigger pulse upon start up but everything I've tried has not worked. I've tried various schemes with capacitors and resistors to try to keep reset low or prevent the trigger from showing, but I'm just not hitting upon the right steps to do this. Admittedly I'm somewhat new to electronics. Does anyone have any tips as to how to prevent the initial start up weirdness from triggering the alarm? Thanks!
