The below attachments show a small project that someone might be interested in building.
The amplifier has the minimum number of components; the schematic came with that of the voice recorder, so I built it as well. There will be amplifiers around with better sound quality. Perhaps a larger 8 Ohm speaker would be beneficial as well.
I have some spare PCBs if anybody is interested.
Regards
Alex Henderson M0TOT
Voice Recorder and Amplifier
Typical Schematic:
If you want to change the record duration, an external resistor is necessary to select the record duration and sampling frequency, which can range from 8 to 20 seconds (4 - 12kHz sampling frequency). Currently, the record duration of this module is 10 seconds as this module by default comes with a 100k resistor ROSC. As per the datasheet, you can select any of these resistors to select a record duration of your choice.
Power Amplifier
If you want an external power amplifier circuit to power some speakers, you can use an LM386, D2283, D2322, TA7368 or MC34119 etc. amplifier IC. The below circuit utilises the LM386 chip.
Specifications:
- Power: 3 - 5V
- IC: USD1820
- Message record length: Up to 10 Seconds
- Speaker: 8 Ohm, 0.5W
- Push-button interface
- Automatic power-down mode
- Can be controlled by a micro-controller
- Sample rate and duration changeable by replacing a single resistor
- Dimensions: 37mm x 54mm
Pin Specifications:
- VCC: 3 - 5V
- GND: Ground
- FT: Feed Through (Feeds the input of the microphone directly to the speaker)
- P-L: Playback level activated. Message is played back when the pin is high
- P-E: Playback edge activated. Message will play when the pin goes high and will continue to play until the end of the message
- REC: Record activate. Will record a message when REC pin is high
