Variobot varikabo Instructions Manual page 44

6) The control circuit
Depending on how the sensors are connected to
the transistors via switch S
sensors FT and FT are arranged in parallel or
1 2
crossed over, the four basic control variants result.
•
Acceleration mode / Braking mode
•
Shadow follower / Light follower
In the circuit diagram, the lateral sensors FT
FT are arranged as shadow followers.
2
The selector switch S
2
position.
If less light falls on the middle sensor FT
transistors switch through more and the motors
become faster. If, on the other hand, switch S
were in the crossed position, the motors would
slow down accordingly.
If, for example, more light falls on sensor FT
voltage at both transistor inputs increases. The
motor M then speeds up and M
2
and whether the
2
1
is in the acceleration mode
, both
3
slows down.
1
As a result, varikabo turns away from the light.
If, on the other hand, the sensors were arranged
crosswise, varikabo would move towards the light.
The two two-color LEDs are connected in series
with the resistor and arranged between the
transistors. They light up red when the current
flows through both transistors and blue when the
and current flows in the other direction through the
motors, provided they are at a standstill.
FT
2
2
FT
3
, the
2
FT
1
M
T
2
2
L
2
R
S
2
L
1
T
M
1
1
+9 V
Bat
S
1