Variobot varikabi Manual page 67

Notes on Lighting
Unlike many other robots, varikabi does not
need to emit infrared light to detect lines or
objects in front of it. This simplifies the
circuit and reduces power consumption.
Since varikabi reacts on brightness
differences in the environment, it is
essential to use a suitable light source.
Note:
The light of LED lamps or fluorescent
lamps has a low red component and
is not well perceptible for varikabi's
sensors.
When using these light sources, a
sufficiently strong illumination must
therefore be provided.
To avoid that varikabi's sensors are not
blinded by the light source, attention must
also be paid to a suitable position in relation
to lamps or windows.
Note:
Most functions can be performed best
under a sufficiently distant lamp or
under a window on the floor.
In the case of lateral light incidence
varikabi would follow this light or its
own shadow instead of driving to the
desired target.
If varikabi is supposed to follow or avoid a
structure on the ground, make sure that the
ground does not reflect light.