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Junior Lab

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on 30 April 2010

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Transcript of Junior Lab

The Clap Switch

Introduction Experiment Conclusion Kristan Armstrong
Takako Hirokawa Theory For our experiment we decided to construct a clap switch through basic circuit components. This circuit enabled us to be able to turn an LED light on and off by simply clapping our hands. In order to contruct this circuit we had to use our knowledge of basic circuit elements as well as common theory through research and analysis. Components Condenser Microphone:

Low RF voltage
Low-Noise Oscillator


Low-Noise Transistors
Low-Voltage Transistors

555 Timer:

Monostable mode
Time: 2.2 seconds
- Resistor One:
Reduces the voltage across the electret microphone
-Resistor Two/Capacitor One:
Blocks DC background caused by condenser microphone
Blocks low frequencies
-Common Emitter Amplifier:
Amplifies the microphone signal -555 Timer (first):
Acts as a monostable switch
Signal input from amplifer into
the trigger pin (below).
Turns on LED for 2.2 seconds
~ T= 1.1* R7*C3
C3 controls the discharge time
R7 minimizes the Vcc voltage

Theory Junior Laboratory Presentation Explanation of the diagram above:

-Electret Condenser Microphone
Compact/ low power
Ferroelectric capacitor allows for non-polarized
voltage source
Sound waves generate change in capacitance
Voltage outputted from change
If we were to continue... Questions? Theory Stage One (Up to LED 1):

- Measured all resistors, capacitors
- Set up first part of the diagram
- To test this, we measured:
Voltage gain:
Theoretically ~ 13
Experimentally ~ 11
Measured Voltage into 555 timer:
Experimentally ~ 8.1 V

It was very exciting to see how and why the
clap lights work, and we look forward to possibly
finishing the circuit. In addition, it was beneficial
to understand how the condenser electret micro-
phone operates.
The seond stage of the experiment would be
assembled and tested.
Full transcript