What is a voice pad you might ask, well the answer is simple, just think of notepad, yes this is a voice recorder. This way you don’t need to carry paper and pen around to get your ideas, to-do’s noted, just record it and play it back.
The gadget described was made by the author for the 2006 Stellaris contest, it uses the LM3S811 microcontroller by Stellaris, SD card for storing the messages, and earpiece for the audio output, OLED display, it even has a buzzer to play ring tones, all hardware used is part of the Stellaris development board.
The messages are played back via the earphone piece, which is powered by PWM, so the audio output stage is a D class amplifier, the volume is controlled by a potentiometer.
The author states that the device can store up to 100 10-30s messages, I say that is plenty of room for personal use, and with the OLED display and menu it is a handy device.
The microcontroller used in this project can be hard to find, but the available source code makes it possible to port the application to another device.