IFD:Printing Acoustic Interfaces/acoustic sensing circuits: Difference between revisions

[[File:receiving_circuit.png| thumb| left| receiving circuit]]

Our actual designs are sender-receiver type circuits, utilizing the radio frequency signal transmission as a means to get rid of mains hum and other interferences. At the same time, this provides the flexibility to detect different frequencies with a single receiving circuit. We will use a high frequency changing voltage (approx. 300Khz) on the sending capacitor plate, that we will receive on the other capacitor plate. When we change the distance between the plate, the capacitance changes and with it, the actual amplitude (volume) of this high frequency tone increases or decreases. To get the actual volume information of this high frequency tone, we use the half wave rectifier. This circuit is commonly used in radio signal receivers, where the amplitude of the frequency of a radio station is changing with the actual transmitted sound wave. This is called Amplitude Modulation (AM Radio).

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.