Sound_detector

[electrogap]

I am using a laser pointer for parking purposes in my garage. It is now activated by having the power in parallel with the opener lamp. However, I wanted it more smart and thought about using a sound detector to detect the noise from the engine. I was playing with an LM-324. I put up to three stages capacitive coupled with gains close to 100 each. The input is an electret microphone. I can have the saturated output I've intended if I speak or whistle from a couple of feet from the mic,however backgorund noise from the car is not detected. Even puting the mic almost touching the radiator there is only some 1 volt signal out.

I do not know if should I try adding more stages or use a more sensitive microphone or forget about sound and think about detecting the spark plug switching with an antenna and work around 1 to 2 MHZ as long as the broadcast do not afected it.

I will appreciate any feedback either with sound or RF option.

JGV.

 

[xray]

prodcuing a one bit adc out of the circuit you have seems like an option. placing a comparator on the end of your three stages at the correct level would give an on or off voltage to occur at a specific volume of noise. one volt of signal that you have seems like an addequate amount to give you some tolerance of volumes from the whistle to the idle of the engine.

Regards;

cy

 

[tdbeng]

I did something similar in my garage that flashes a green light when the car is close enough to the back wall (wife was always running into the trash cans!). I used a linear inductive proximity sensor to detect the distance to the metal grid on the front of the car. Would this be an option for you? Or possible an IR sensor?

The sound detection sounds complicated. If you're into DSP, I'm sure there are certain noise characteristics of a car engine that could be detected. Good Luck!