The Motor Mouth Talking Head

Takes in audio from a tape recorder or computer sound card and operates a jaw using a small 3 to 6 volt motor in time with the audio signal. Uses two IC's a 741 op-amp (U1) and a 7812 postive voltage regulator 12 volts (U2). Very little of the audio signal is used and it does not need to be amplified. Audio input can be any suitable source with an impedance of 4 to 16 ohms, the speaker shown in the schematic is 8 ohms. The SCR (silicon controlled rectifier) is 200 volts, 6 amp. The SCR when powered "on" rectifies the alternating current supplied by the transformer to pulses of direct current to run the motor. The use of alternating current (AC) to the SCR prevents the SCR from locking in the "on" mode (which would happen if DC were used in the SCR/motor circuit) Info from the original article "Fred-the-Head" by Richard L. Pearson, 1989 Popular Electronics Hobbyists Handbook, pages 23-27. The circuit is reproduced below.

Fred-the-Head circuit by Richard L. Pearson

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