Talking Fish Hack
These items were sold nationally several years ago. The fish would sing, open its mouth, turn its head, and flap its tail.
After removing the back panel, all of the existing electronics were removed leaving only the 3 servo motors, speaker and photocell.
The reworked insides are shown here. Wires from each of the motors and from the photocell were soldered to a terminal strip (made of copper stripes on a circuit board).
The controller board (lower left) connects using a 20-pin
dual row header that mates with a ribbon cable connector.
The closeup of the board shows the PIC16F819, 3 NPN darlington power transistors, a 24LC512 eeprom, an MCP41010 (used for D/A) and an LM386 speaker driver.
The movements in this device are all controlled by small motors driven in one direction only. Spring mechanisms accomplish the reverse directions. That makes the control device much simpler - it only has to power the motors in one direction.
The photocell is recessed about half an inch making it responsive mostly to motion directly in front of the device. When a light level drop is sensed, one of several phrases is selected at random and a code sequence is executed. The phrases are stored as separate words so that the mouth mechanism can be activated for each of them. See the source listing for details.
For detailed information on constructing you own sound eeprom go here.