A bicore together
with a L293 can be used to control turning and reversing of a
phototropic tank as follows:

A single phototropic bicore is connected to the inputs of two of the
quad L293 motor drivers (the bicore drivers). The two bicore outputs
have complementary waveforms that controls the duticycle or ON time
of each L293 driver . The inputs of the other two L293 drivers can be
connected to the outputs of two obstacle sensors (sensor driver).

The outputs of the L293 bicore driver are connected to the left and
right track motors while the other side of each motor is connected to
a sensors drivers.

Normally the light on the photodiodes controls the dutycyle of the
bicore outputs. This adjusts the forward dutycycle of the motor
currents that control the speed of the left and right motors to make
the tank follow light.

When an obstacle is detected with a tactile sensor and delay (Nu
neuron), the sensors driver that controls that side motor goes high
and reverses that motor rotation so that the tank will rotate away
from the obstacle.