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IFD:Printing Acoustic Interfaces/acoustic sensing circuits (view source)
Revision as of 19:56, 27 June 2019
, 27 June 2019→Printed Capacitive (Condenser) Microphone
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The sending circuit is a very simple triangle wave generator using parasitic effects of the circuit board to reach high frequencies and at the same time provide minimal component counts. The output of the sending circuit is putting and removing charge to one plate of the printed capacitor in the shape of a high frequency triangle wave. | The sending circuit is a very simple triangle wave generator using parasitic effects of the circuit board to reach high frequencies and at the same time provide minimal component counts. The output of the sending circuit is putting and removing charge to one plate of the printed capacitor in the shape of a high frequency triangle wave. | ||
[[File:receiving_circuit.png| thumb| left| receiving circuit]] | [[File:receiving_circuit.png| thumb| left| receiving circuit]] | ||
The receiving capacitor plate's capacity is modulated by the high frequency triangle wave from the first plate, as well as the distance from this first plate. The distance modulation in audio range (0-20kHz) is what we are interested in detecting. First we pre-amplify the modulated signal from the receiving capacitor plate with a charge mode amplifier, than we detect the envelope of the high frequency wave with a half wave rectifier and a low pass filter and finally amplify and buffer the resulting envelope. This corresponds to the distance of the two capacitor plates in audio rate. | |||
[[File:microphone_amp_tl072_Steckplatine.png | thumb|left| TL072 Version ]] | [[File:microphone_amp_tl072_Steckplatine.png | thumb|left| TL072 Version ]] | ||