We will now use the ISD1820 IC to build a voice recorder. The ISD1820 is a dedicated voice recorder IC and we will be using the reference circuit contained in the datasheet.
The ISD1820 works at a maximum of 3.3V, so make sure you connect the right voltage output before powering it ON. An electret microphone is used to capture audio and the output from this is passed to the IC. We have 3 switches that are used for recording and playback along with a status LED.
Resistor R2 is used to set the recording duration and sample rate. A higher sample rate produces a much better recording but this sacrifices the recording time.
The IC starts recording audio the moment the REC button is pressed and the RED LED is used to indicate this. Pressing the PLAYE button will cause the audio to play till the end, while pressing the PLAYL button will cause the audio to play, as long as the button is pressed. The PCB also contains holes for a header pin which can be used to interface the IC to a microcontroller. This will allow you to trigger the recording and playback remotely.