IFD:Printing Acoustic Interfaces/acoustic sensing circuits: Difference between revisions
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[[File:receiving_circuit.png| thumb| left| receiving circuit]] | [[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). | 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). | ||
[[File:sender.png| thumb| left| triangle wave generator]] | |||
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 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. | ||
Revision as of 19:45, 27 June 2019
Printed Transformer Type Microphone
In the first part of the course we explored the possibility of a transformer based microphone, involving printed coil structures on paper. Unfortunately the printed structures have shown a large resistance, making them unsuitable for inducing magnetic field. This is because the strength of the magnetic field is proportional to the amount of current flowing through the coil, which, in turn, is limited by the resistance of the coil. It was found, that by using our printed inkjet techniques, the resistance of coils was too large by approximately two orders of magnitude. Goal: 4-20 Ohms, Actual circuits: 500-1000 Ohms. You can find the explored circuits below
transformer microphone and 555 timer oscillator (outdated circuits)
Printed Capacitive (Condenser) Microphone
However, the circuits where still capable of sensing vibrations, because of another effect that was not anticipated, but stronger in the actual circuit: The capacitive effect of the two opposing coils. This capacitive effect can be made larger by providing a bigger overlapping area of the two conductors that form the microphonic surface. That simplified our print designs a little, because we were not forced to print coils as two port devices, but could use two rectangular shapes with a single port each. Leading to lesser connections and no jumper wires on our paper printed microphones.
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.
