#### ddaann11

Joined May 6, 2011
2
Hello all,
This year for my introductory Electronics course, we have been assigned to create a clapper circuit that turns on an LED after one clap, and Turns the LED off after two claps. So far I have the microphone wired to an omp-amp, and then after that I am really very lost on where to go next.
I was talking to the instructor and he hinted that a monostable 555 timer would be a nice place to go after the op-amp. I understand the capabilities of a monostable 555 timer, just not why it would be useful after the op-amp(which is inverted by the way). Then there is the logic which has to recognize the number of claps (within a certain time limit, aka where the 555 timer comes in again), which I am confused on.
The last main question I have so far, is how a logic gate of any type could recognize two successive signals coming from the wire and turn it into memory.
Any Help would be appreciated, thank you.
Daniel

#### JDT

Joined Feb 12, 2009
657
I have attached a simplified sketch of what your circuit has to do.

First, amplify to audio signal from the microphone.
Next, rectify the amplified signal to produce a DC level proportional to the loudness of the sound.
Then, detect a threshold DC level and use this to switch your LED.

So that it switches on at the first clap and off at the second, I suggest using a "toggle" flip-flop as shown.

The threshold detector has to produce a sharp edge as the slowly changing DC level goes above and below the threshold. I have drawn a "schmitt trigger" for this. This can be part of a logic IC such as the 4093 or you could make it with an op-amp or comparator and feedback resistors. For the flip-flop you could use an IC like the 4013.

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#### ddaann11

Joined May 6, 2011
2
Thanks JDT, I appreciate the post,
I showed this to my TA which started us on a discussion that helped to answer a lot more questions that I had in the back of my head. I appreciate it

#### Audioguru

Joined Dec 20, 2007
11,249
You must think about the difference between two hand claps and two barks from a dog.
Maybe a highpass filter will pass the hand claps and reject the low frequencies of a dog barking. Maybe your circuit will work when you shout, "OPEN NOW" or "BEEP BOOP" but will not work when you shout a single word.