Heruncula,2007

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Comissioned by the Palouse Discovery Science Center as part of an eduational project centered on the wonder of the brain. It was renamed "Sarah Bellum". It awakes to sound by opening its eyes and responding to the motion and sounds of a visitor producing a dance of light in an impressionistic interpretation of neural stimuli.



The ear circuits consist of an amplified electrect michrophone, driving a charge pump, and supplying the output voltage as an average proportional sound level to the MCU through pins 2 and 3. There are two of these, -one for each ear. The voltage is converted to a digital number, processed and the output is sent to the HCT164 shift register that runs the sequence of yellow leds that indicate a stimulus.At a pre-set level, the ear "nerves" are also triggered.

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Eyes are a pair of standard three terminal passive infrared detectors. Their output is a pulse delivered when motion is sensed. The pulses drive pins 40 and 39 of the MCU, and also control an orange led in each lens.



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The eyelid mechanism is controlled by an h-bridge circuit that switches an electromagnet on and off at two polarities. The mechanism is bistable, that is, it will remain in it's last set position without requiring a holding current. A pulse of one polarity will open the lids, and a pulse will close them. The pulse widths and timing are controlled by the MCU.

The medulla shift register is located just below and behind the MCU, and is similar to the ear shift circuit. Note that the MCU pin 23 controls the brightness of both this circuit's led and the three lobes.



Three identical circuits provide the switching for the three lobes' led's. These circuits are located in the plane that divides the hemispheres. They are constructed in three different configurations, but are electrically identical. Patterns of switching (dances) are calculated by the MCU, which modulates the dances dependent on stimuli from the eye and ear circuitry.
The Master Dimmer, Pin 23 of the MCU provides a pulse-width-modulated stream that determines the brightness of the lobes and the medulla register.



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