Make a Single Chip Programmable Voice/Audio Recorder

The article explains a single chip circuit which can be used for recording short voice clips or any audio clip ranging from 20 to 60 seconds.

About the IC APR9600

The incorporated IC APR9600 is a programmable voice recorder chip which facilitates infinite number of recording/erase of audio files in it as per user preference.

The recording or storage of the audio can be done through an integrated electret mic or via any line out or RCA port of an audio reproducing device.

However since the IC is a low bit device does not support Hi-Fi recording rather low quality music.

The sampling rate or the frequency response is limited to just 8 kHz max that's pretty ordinary if we compare it with the specs of modern Hi-Fi equipment.

Nevertheless, the IC is a stand alone device which does not depend on any external circuits, just plug it in, and it starts recording whatever voice data is fed across its input pins. Moreover since the data can be erased and refreshed any number of times, the unit becomes completely programmable and a pretty useful gadget.

Image courtesy:  https://www.datasheetcatalog.org/datasheet/aplus/APR9600.pdf

Simulation and Working

The proposed circuit of a programmable single chip voice recorder/player utilizes the IC APR9600 as the main processor of the circuit.

It's a 28 pin IC which can be very easily and quickly configured for getting the required results by adding a handful of common passive electronic components.

All the pin outs of the IC are specified by their individual functions, and the components are accordingly attached with the respective pinouts.

For example pin#28 and pin#27 are assigned as the trigger inputs for initiating playback and recording functions.

Sliding the connected switch toward right initiates the playback action while toggling it  toward left puts the IC in the recording mode.

The IC also has appropriate visual indication options which provide the user with instant information regarding the position of the circuit.

The LED at pin#8 indicates the end of a playback file session.

The LED at pin#10 stays illuminated for so long the audio is being played, indicating circuit "busy"

The LED at pin#22 indicates through rapid flashes regarding the playback or recording modes of the IC.

The input data is normally picked from the mic which is appropriately connected across the pins 17 and 18 of the IC.

When the slider switch is pushed toward the recording mode, any audio entering the mic gets stored inside the IC until the specified time elapses.

The sampling rate of the IC can be set as per the user preference. Lower sampling rates will provide longer recording/playback periods and vice versa.

Longer periods would also mean lower voice quality while shorter periods of recording spec will produce relatively better sound processing and storing.

The entire circuit operates with a 5 volt supply which can be acquire through a standard 7805 IC after rectification from a standard transformer bridge capacitor network.

The audio output may be derived across pin#14 and ground which must be terminated to an audio amplifier so that the data can be heard with proper volume.

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