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DIY sound triggered switch

Updated on November 7, 2012

With this sound activated trigger, everyone is able to manage many different appliances. Fro example, in your household you can activate any appliance by clapping your hands or when the door closes or knocks, and the light bulb in the hall turns on in just a few seconds. Hmmm, pretty interesting, I know. That is why I want to share it with you.

It wont cost much to build this project, but it will definitely be very handy in every household. The point is actually that in the circuit we must use voltage in range from 0-100 mV. I used 10 kΩ variable resistor, 5kΩ resistor and +15V voltage source, in order to generate the desired voltage level of approximately 0 to 10 V. The voltage divider 100:1 is used for this purpose, which actually lowers the voltage range to a 0 to 100 mV range. The Ei souce signal represents the signal from the microphone, and on the output the device is connected to the alarm.

Any noise that will occur will cause AC voltage on the microphone. The first positive oscilation from Ei greater than Vref brings Vo to +Vsat. In this case through the diode flows current of 1 mA to the gate of SCR (Silicon-Controled Rectifier). In initial conditions, the anode and cathode of the SCR act as open breaker. Once the SCR is activated, the circuit works until the anode and cathode are opened again. The schematics is provided below. I hope that you enjoyed in this article.

Sound triggered switch schematics
Sound triggered switch schematics
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