This circuit consists of a microphone which can enable or disable a light attached to it, by the sound of applause,

when applause for the microphone is detected, the signal is transmitted to a preamplifier, which consists of a transistor and resistors

The output pulse of 555 activates the clock inputs of a JK-type counter, the integrated 7493.

The 7493 is configured to use one of the flip-flop internal which will keep the active signal, applause is needed for the output Q1 of the flip-flop through the high state and activate the Q1 transistor, which in turn activates the relay .

The transistor energizes relay coils allowing the bulb switch.

List of components

Breadboard
Transistors 2n 3904
Timer 555
Integrated counter 7493
Diode 1n 4004
Relay JQC-3F
Battery 9v
Capacitors & resistors
Wire UTP

Step 1: Preamplifier

In this step we build the preamplifier will be necessary for our microphone, as the voltage is very small, must be amplified.

The preamplifier is a 2N3904 transistor, configured feedback. The positive pin of the microphone is connected to Vi, and the other to ground. The amplified audio output is on pin Vo.

Step 2: Timer 555

The 555 timer aims to convert the analog audio signal coming from the preamplifier, an easy digital signal processing. Once again the input is Vi and output is Vo

The timer output is high (1), and then receives the audio signal entering the trigger pin, alternating output low (0).

This shift from high to low state, we will be useful to create a rising edge that was used in the Flip-Flop.

Step 3: Flip-Flop

This step is important, here the pulse will remain activated to allow the lamp, until next slap sound

The applause generates a high state, but is very short (it takes what it takes slap). The flip-flop does is hold, the high state generated by slap.

Was used for this project a counter 7493, which has 4 Flip-flop's internal. You can also use Flip-flop's common as 7476 or 7473.

Step 4: Power Stage

At this stage, the pulse remained at the output of flip-flop is taken and applied power stage.

We use a fixed bias transistor as a switch to energize the relay coil. The diode is used to protect the transistor.

We can feed the relay with a voltage of 9-12 v. In this way we can light bulbs work with 12 volts. There are relays which can be fed with more voltaje.

Step 5: Complete Circuit

The last step would bind all, as shown in the picture. It can be seen that input Vi is the microphone input and output Vo is the lamp.

In the picture you can see that the relay is powered by 12v, but you can also use 9v battery, and thus can be connected to relay any device that is powered with 9 volts.

The other components are fed 5v. You can get this voltage by applying a "dimmer" a 9V battery.