Clap activated switch. With optional latching.

402

04:52:26

The input represents a mic , powered by 9v , modulating the signal by 20mv.
This is amplified 100 times by the op amp. ( LM324)  giving out 1v ( only amplifying the + side )Switch on and off the oscilloscope ( the eye button ) to see the signals.

The amplified clap is fed into a comparator ( use ref to set level of back ground noise)  this turned on an LED  .( could use an optometrist coupler to drive a camera Flash).

The loop back from the output of the comparator to the input , should latch the output , but in the simulation this does not happen!

published 9 years ago

FitFat

9 years ago

Please think about the case of the output of 1st op-amp is 0V (GRD), and of 2nd one (comparator) is 9V. What does the voltage of blue point become? Then the output will not be latched. Please see http://everycircuit.com/circuit/5838201014452224 .

FitFat

9 years ago

So, 1st op-amp works as pulling down the voltage too, not only pulling up it.

scuba_2

9 years ago

The first op amp amplifies the 20vm clap detected by a mic ( normally there would be a mic and resistor feeding the capacitor) this is amplified for use on the comparator .

FitFat

9 years ago

Yes, I know. I mean if the output of the first op-amp becomes 0V, the blue point voltage will be pulled down as same level, either the output of the 2nd comparator is any voltage. Therefore, that will not be latched.

FitFat

9 years ago

To latch the outout, you have to keep the bluepoint voltage higher than the (-) input of the comparator. But if the bule point voltage moves higher by external causes, it is going to be feedbacked to the first op-amp, then it will be turn back to the original lower voltage.

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