Variobot varikabi User Manual

Safety Instructions for Parents and Children

Attention! Please keep away
from children under 3 years.
Danger of suffocation by
swallowing small parts.
Risk of injury due to sharp tips and edges of
individual components. We reserve the right
to make technical changes.
Please note: Only suitable for children over 8
years. Use under the supervision of adults
recommended. Please read the instructions
before use, follow them and keep them at
hand for reference. Please keep the
packaging.
Battery: The kit requires a 9 V battery, which
is not included in the package due to limited
storability.

A short-circuit of the battery must be
avoided, because it can cause overheating
of the cables and an explosion of the
battery. After use, the battery clip must be
removed of the battery. Non-rechargeable
batteries must not be charged. There is a
risk of explosion.
Deformations of the batteries must be
avoided. Used batteries must be disposed of
according to environmental regulations.
Please note: The LEDs, sensors and
transistors must be inserted with the correct
polarity for the circuits to work. The two
transistors have a different designation and
must not be confused. The motors must be
connected correctly.

General Information

All circuits presented in this manual have
been developed, checked and tested with
the utmost possible care. Nevertheless,
mistakes cannot be completely excluded.
The author is liable in cases of intent or
gross negligence in accordance with the
statutory provisions. For the rest, the author
shall only be liable in accordance with the
Product Liability Act for injury to life, body or
health or for culpable breach of essential
contractual obligations. The claim for
damages for the violation of essential
contractual obligations is limited to the
contract-typical, foreseeable damage, unless
there is a case of mandatory liability
according to the Product Liability Act.

The product has been manufactured in
accordance with the applicable European
directives and therefore bears the CE mark.

The intended use is described in this
manual. In the event of any other use or
modification of the product, you are the only
responsible for compliance with the
applicable rules. Therefore, assemble the
circuits exactly as described in the
instructions.

The crossed-out dustbin symbol means that
this product must be recycled separately
from household waste as electrical and
electronic waste. Your local authority will
tell you where to find the nearest free
collection point.

Introduction

We are pleased you have chosen this
versatile robot assembly kit. varikabi offers
you an exciting and playful approach to
electronics. You will certainly have fun and
variety with varikabi for a long time.

Varikabi's "muscles" are two motors, his
"brain cells" two transistors. The simple
control circuits are placed on a small
breadboard and are therefore easily

modifiable.
With the help of a clever combination of

three brightness sensors varikabi perceives
the smallest contrasts in its environment and
reacts to them in many different ways.
Thanks to a selector switch and by aligning
and switching the sensors, you'll explore
twelve different functions and amazing
behaviors.

varikabi can do a lot:

- Overcome obstacle courses

- Follow dark or light lines

- Track or move objects

- Search, track or circle light

- Trace or circle shadows

- Circle on light or dark areas

Content

1) Assembly
varikabi is available in the seven colors red,

blue, green, neon green, yellow, pink and
black. Regardless of the color variant, there
are seven different animal models to
choose from. Numerous illustrations show
you step by step how to assemble them.

S. 9 varikabi as a Dog
S. 17 varikabi as a Sea Lion
S. 23 varikabi as a Frog
S. 29 varikabi as a Bird
S. 35 varikabi as a Giraffe
S. 43 varikabi as a Mouse
S. 51 varikabi as a Beetle
S. 60 varikabi - Fischertechnik

2) Functions
The experimentation manual explains the

twelve functions of varikabi. It will show
you how to build the appropriate circuits,
connect the motors and set the three
sensors. Finally, find a fault diagnosis in
case something does not work as expected.

3) Operating Principle
You will learn how the different control

circuits and components of the kit work. You
will learn varikabis behaviors and
understand how they are caused.

This part of the manual is still under
construction and will be updated
continuously.

1) Assembly

What you need

• 9 V block battery or 9 V battery

• pliers and side cutters

• black duct tape (for varikabi FT)

• about one hour time

The seven varikabi models

The components

varikabi as a Dog

1)

2)

3)

4)

5)

6)

7)

varikabi as a Sea Lion

1)

2)

3)

4)

5)

varikabi as a Frog

1)

2)

3)

4)

5)

varikabi as a Bird

1)

2)

3)

4)

5)

varikabi as a Giraffe

1)

2)

3)

4)

5)

6)

7)

varikabi as a Mouse

1)

2)

3)

4)

5)

6)

7)

varikabi as a Beetle

1)

2)

3)

4)

5)

6)

7)

8)

varikabi - Fischertechnik

The components

1)

2)

3)

4)

2) Circuits and Functions

The different circuit variants allow varikabi twelve functions. The circuits and features of the
functions are described below in detail.

varikabi stands still

varikabi drives slowly varikabi drives fast

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.

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.

If varikabi is supposed to follow or avoid a
structure on the ground, make sure that the
ground does not reflect light.

Notes on Lighting

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.

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.

Breadboard Resistor

With a breadboard simple electronic circuits
can be set up and changed very quickly.

Our small breadboard has eleven rows of
five pins each connected internally. The
outer two rows are used for the power
supply (+/-). The rest are labeled with the
numbers 1 to 9.

The fifth row in the middle is concealed at
varikabi with the black cable tie and is not
needed.

The resistor limits the current of the two
LEDs. The colored rings indicate the value of
the ohmic resistance, which in our case is
150 Ω (ohms).

Bend the connecting wires of the resistor at
a distance of 10 mm and shorten them to a
length of approx. 15 mm. Then put the
resistor in the center of the breadboard.

Transistors

Since varikabi's drive motors require a much higher current than the
sensors can supply, amplifiers are needed. A transistor is a simple
three-terminal electronic amplifier.

To make sure that the gain is sufficiently high, so-called Darlington
transistors are used, which already contain two series-connected
transistors.

The right and left motors require equivalent transistors, a so-called
PNP and an NPN transistor. They can be distinguished by their
imprint BC516 (PNP) or BC517 (NPN).

Bend the outer two legs slightly apart so that the transistors fit well
into the breadboard. Then insert them into the breadboard according
to the illustration on the left and right of the resistor.

Caution:

The two transistors BC516 and BC517 must not be mixed-up and
must be inserted turned differently.

Sensors

varikabi compares the brightness at its three sensors. Depending on how the so-called
phototransistors are aligned, varikabi perceives impressions of the ground, in front or above
itself. A phototransistor (FT) can be imagined essentially as a variable resistor whose
resistance decreases as the brightness increases.

Caution:

The phototransistors must be installed correctly
polarized. The + side has a shorter leg and a
flattening on the protruding collar of the case.

However, you must pay attention to the correct polarity of
the phototransistor. The sensors are connected to the
breadboard in all 12 circuits in the rows +, 4, 6 and -.
Therefore, bend the connections slightly apart according
to the illustration.

The following pages describe how to install the three
sensors for each function. Select a desired function and
align the sensors accordingly.

1) Following Dark Lines

• Searches for a dark line
(e.g. black tape)

• Drives along the line

• Accelerates on straight

stretches and brakes in curves

Circuit: Shadow Follower / Acceleration Mode

With the distance between the outer two sensors you
can adjust the accuracy with which varikabi is
supposed to drive on the line. Ideally, they are a little
off the line. If they are too close to the line, varikabi
will permanently adjust the direction and drive
serpentines.

In addition, it will not be able to activate its turbo,
because for this more light must fall on the outer
sensors than on the one in the center.

2) Following Light Lines

• Drives along a bright line
(e.g. white tape on a dark
background)

• Stops at the end of the line

Circuit: Light Follower / Braking Mode

If you do not have white adhesive tape, you can place
white sheets of paper on a dark floor, for example.

With the distance between the outer two sensors you
can adjust the accuracy with which varikabi is
supposed to drive on the line.

To make varikabi stop at the end of a line (on a dark
background), direct the center sensor further down
than the two lateral sensors.

• Traces a light on the ground
or a lamp in front of him

• Stops in front of the light

• Stops when a shadow

appears over him

Circuit: Light Follower / Braking Mode

The ambient light should not be too strong for this
function, so that the contrast is strong enough.

Align the side sensors in parallel or just slightly to the
side so they can simultaneously keep a frontal light in
sight.

The more light hits the outer and the less the center
sensor, the sooner varikabi will come to a standstill.
This ratio can also be adjusted with the inclination of
the center sensor.

3) Tracking Light

• Moves towards dark objects
in front of him

• Keeps distance and stops in
front of them or tracks
moving objects

Circuit: Shadow Follower / Braking Mode

Adjust the distance of the lateral sensors to the size of
the object to be tracked. The further forward they are
directed, the more exactly varikabi will follow the
object. However, if they are both directed to the
object, varikabi will not be able to stop in front of it.

Use the tilt angle of the center sensor to adjust the
distance to the object being tracked. The more you
point it down, the closer varikabi will approach the
object.

4) Tracking Objects

• Stands still when no dark
object is in sight

• Starts moving when an object
is in front and follows it

• pushes small things forward

5) Pushing Objects

Circuit: Shadow Follower / Braking Mode

Adjust the distance of the lateral sensors to the size of
the object to be tracked. Both sensors should have the
object in view at the same time.

Adjust the angle of inclination of the middle sensor so
that it is only slightly over the object. If the middle
sensor points too steeply upwards, varikabi remains
constantly in motion and can only be stopped by a
shadow from above.

• Stops in case of dark obstacles,
navigates between them and
then accelerates again

• Overcomes an obstacle course

6) Avoiding Obstacles

Circuit: Light Follower/ Acceleration Mode

In order for varikabi to reliably avoid obstacles, these
must be darker than the ground.

Align the lateral sensors about 45° to the side and slightly
to the ground. The further the sensors are directed
downwards, the closer varikabi will approach obstacles
before swerving.

Adjust the tilt angle of the center sensor in the way that it
is only slightly directed above the obstacles so that
varikabi will be able to accelerate on free track.

• Stays on a bright surface (e.g.
illuminated table in the dark)

• Avoids dark obstacles

• Accelerates and escapes shadows

appearing over it

7) Avoiding Dark

Circuit: Light Follower/ Acceleration Mode

The bright area can be e.g. your room floor or a clear table
illuminated from above. You can also place white sheets
of paper on a dark background. Avoid lateral light
incidence from windows. For varikabi to recognize the
edge of the table well, the optimum angle of inclination
of the two lateral sensors must be found.

Caution: If you hold your hand above varikabi, it will only
drive straight ahead without paying attention to its
surrounding.

8) Avoiding Light

• Stands still on a light surface

• Drives steadily on a dark ground

• Turns away from light or stops in

front of it

Circuit: Shadow Follower / Braking Mode

For the dark background, for example, you can cut black
paper and place it on a light floor. The surface should be
round and have a diameter of at least 30 cm.

Adjust the inclination of the two lateral sensors in the way
that varikabi will turn at the edge in time.

Adjust the tilt angle of the middle sensor in the way that
varikabi will always keep moving on the dark surface but
stops on a light surface.

9) Following Shadows

• Avoids light and seeks shade

• Drives towards a shadow

• Stops in the shadow

• Tracks the shadow as it moves

Circuit: Shadow Follower / Braking Mode

Choose a place outdoor or underneath a light source,
which is placed at least one meter high. Your hand is the
best shadow. However, be careful not to wear clothes
with dark sleeves, otherwise varikabi would prefer to
follow the shadow of your arm.

When you hold your hand over varikabi, it stops. Then
slowly move your hand forwards or sideways so that
varikabi can follow it.

10) Search Light

• Searches for a light above him
and drives towards it

• Stops under the light

• Turns away of shadow and drives

back into the light

Circuit: Light Follower / Braking Mode

For this experiment you need a dark room and a lamp
about 30 to 100 cm above varikabi. Ideally, you can also
move the lamp. However, a flashlight is not very suitable
because of its focus.

The more you direct the center sensor upwards, the
further varikabi will move towards the center of the lit
area before it stops. If you hold your hand between
varikabi and the lamp, varikabi will try to return into the
light.

11) Circling Around Light

• Looks for a light and drives fast
towards it

• Then below the light it moves on
slowly in circles

• Accelerates when shadow is above

Circuit: Light Follower/ Acceleration Mode

For this experiment you need a dark environment and a
lamp about 30 to 100 cm above varikabi. A flashlight is not
suitable because of its strong focus.

If you place varikabi on the ground in some distance from
the lamp, it will quickly approach the light.

Below the lamp, it will slow down and keep turning in
order not to move away from the lamp. With the inclination
of the sensors you choose at which distance varikabi will
make the turn.

12) Circling Around Shadow

• Turns away from light

• Accelerates when shadow is

above

• Tries to stay in the shade and
turns again and again

Circuit: Shadow Follower / Acceleration Mode

Choose a place outdoors, but not in the sun, or a room
with uniform ceiling lighting. If you hold your hand or a
larger object over varikabi, it will accelerate briefly and
then turn steadily in order not to move out of the shadow.

With the inclination of the sensors you set when varikabi
will turn back each time. The two side sensors must
always be directed slightly further backwards than the
center sensor.

Cable Bridges

The blue cables connect the sensors (FT2,
FT3, FT1) with the transistors (T2,T1).

Depending on whether you connect them
directly or crossed, varikabi will respond
differently to a shadowing of the sensor FT3:

FT

2

FT

3

FT

1

FT

2

FT

3

FT

1

The description of the 12 functions indicates
whether you need to select the acceleration
mode or the braking mode for each circuit.

Plug the blue wires into rows 1, 4, 6 and 9
according to the illustration.

 Acceleration mode: cables parallel

 Braking mode: cables crossed

LEDs

Unlike incandescent bulbs, LEDs must be
properly polarized for them to light up. The
shorter leg and the flattening on the
housing mark the negative connection (–) of
an LED.

Depending on the color you have two red,
blue or green LEDs in your assembly kit.
Depending on whether you have selected
the braking mode or the acceleration mode,
the LEDs must be bent and plugged-in in a
different way.

Finally, put the two white silicone sheaths
on the LEDs.

Note:

varikabi's eye-LEDs will only light up at
high speed or at standstill. This means
always when the center sensor FT3 is
shaded.

T

2

T

1

varikabi gets faster

T

2

T

1

varikabi slows down

Acceleration Mode Breaking Mode

Connection of the Motors

varikabi moves with the help of two
particularly slow and quiet DC motors. With
the black rubber caps varikabi therefore
requires neither a gear nor wheels.

The speed of the motors is set by the level
of the applied voltage. This voltage is
controlled with the help of the transistors or
the sensors respectively.

Depending on which transistor (T2, T1) drives
which one of the motors (M2, M1), the
following behaviors arise:

The following diagram shows how the
cables are to be mounted in the rows + 2 8
–. Depending on the selected function,
connect the motor cables as light or shadow
follower.

 Light Follower: red cables are inside

 Shadow Follower: red cables are outside

The rotation direction of the motors depends
on the polarity of the applied voltage. In
order for varikabi's engines to spin forward,
make sure that the red connections always
cross and the black ones run parallel.

Note:

By connecting the motors differently,
you determine whether varikabi will be
driving toward the dark or the light.

T

2

M

2

T

1

M

1

Light Follower

T

2

M

2

T

1

M

1

Shadow Follower

Light Follower Shadow Follower

Caution:

The red cables

are crossed

connected!

Power Supply

In order to put varikabi into operation, the
outer two rows of the breadboard now
have to be supplied with power.

To do this, lead the battery cable with the
two plug-in connections from underneath
through the gap between the bracket and
the battery.

Then insert the contacts of the battery cable
to the positions on the breadboard indicated
below. To avoid a short circuit between the
plugs, leave them in the breadboard and
use the clip connector on the battery to turn
varikabi on and off. For a battery change,
you can pull out the battery sideways.

Fault Diagnosis

Problem Possible Reasons

varikabi does not move at all. • The left and right sensors are connected with the

wrong polarity.

• A battery cable is not inserted correctly in the
breadboard or the battery clip is not on the 9V
battery.

• The battery is empty or defective.

• The rubber caps are too far on the motor shafts.

Only one of the motors is running. • The left or the right sensor is connected to the

breadboard with the wrong polarity.

• A transistor is connected to the breadboard with
the wrong polarity.

• A connection cable of the motor is not inserted
correctly in the breadboard.

• A rubber cap is pushed too far on the motor shaft.

A motor turns backwards. • This motor is connected with the wrong polarity.

Problem Possible Reasons

varikabi only drives straight
ahead.

• The center sensor is connected incorrectly.

The two LEDs do not light up. • One or both LEDs are inserted with the wrong

polarity.

varikabi gets stuck on the ground. • varikabi is not placed well or too uneven on the

cable ties.

• The surface is too bumpy for varikabi.

If none of these causes apply to your problem, check carefully that all components are
installed as described in the construction plan.
If you need help, please contact us with a detailed error description and preferably a
photo of your robot:

[email protected]

3) Operating Principle

Depending on how the sensors are connected to the transistors and which motor is driven by
which transistor, there are four basic control and circuit variants, which are shown on the
following pages.

• Acceleration mode / Shadow Follower

• Acceleration mode / Light Follower

• Braking mode / Shadow Follower

• Braking mode / Light Follower

All other features of the 12 functions are set by aligning the sensors.

The obliquely drawn connections represent the blue cable bridges between the sensors and the
transistors.

The two LEDs are connected in series with the resistor and arranged between the transistors. In
Acceleration mode they light up when the current flows through both transistors. In Braking
mode they light up when the current flows through the motors in the other direction, as long
as they stand still.

Circuit: Acceleration Mode/ Shadow Follower

FT

2

FT

3

FT

1

T

2

T

1

L

2

L

1

M

2

M

1

R

Bat+9 V

Circuit: Acceleration Mode/ Light Follower

FT

2

FT

3

FT

1

T

2

T

1

L

2

L

1

R

Bat+9 V

M

2

M

1

Circuit: Braking Mode/ Shadow Follower

FT

2

FT

3

FT

1

T

2

T

1

L

2

L

1

M

2

M

1

R

Bat+9 V

Circuit: Braking Mode/ Light Follower

FT

2

FT

3

FT

1

T

2

T

1

L

2

L

1

M

2

M

1

R

Bat+9 V

The Transistors

A transistor is a simple electronic amplifier with three connections:
base (B), emitter (E) and collector (C).

At a sufficiently high voltage of about UBE= 0.7 V (V = Volt) between
base and emitter, the transistor reduces the resistance between
collector and emitter and - it is said - it switches through. The
collector current IC for ordinary transistors can be about 100 to 800
times larger than the base current IB.

varikabi uses Darlington transistors with a very high current amplification of
30 000. To supply the motor and LEDs with a current of 0.03 A (amps) = 30
mA (milliamperes), a base current of only 1 μA (microampere) is required:

30 mA / 30.000 = 0.001 mA = 1 µA
A Darlington transistor consists of two transistors connected in series and

requires about U

BE

=1.4 V instead of 0.7 V to switch through. To ensure that
the motors react to the sensor signals in opposite directions, varikabi uses a
complementary pair of transistors:

one PNP transistor for T1 (BC516) and one NPN transistor for T2(BC517)

I

C

I

B

I

B

I

C

T

2

T

1

The adjacent figure shows a simple circuit with a battery, a
motor and an NPN transistor. Underneath, the corresponding
circuit is shown with a PNP transistor. The current flows in the
direction of the black arrow from plus to minus in both cases.

There are three different basic circuits with a transistor.
varikabi uses the so-called collector circuit.

It is called collector circuit because the collector (C) is
connected to a constant voltage (battery).

The red arrows symbolize the voltages. You can notice that
the voltage at the motor UEis lower by the base-emitter
voltage UBEthan the base-voltage UB.

UE= UB– UBE= UB– 1.4 V

U

BE

U

B

U

E

Note:

Because the voltage at the emitter (E) follows the
voltage at the base (B) except for the difference
of UBE, this circuit is also called emitter follower.

With the control voltage UBand a very low current IB, the
voltage UEand thus the speed of the motor can be controlled.

U

E

U

B

U

BE

The Sensors

varikabi's phototransistors (FT) are similar in design to a transistor. The
collector (C) is on the plus side and the emitter (E) is on the minus side.
Instead of a basic connection, however, they have a light-sensitive area.

The incidence of light determines the permeability between the collector and
the emitter.

The circuit diagram shows that the three phototransistors FT1, FT3and FT2are
all connected. They say they're in series. This series connection results in a so­called voltage divider, which divides the voltage of the 9 V battery depending
on the illumination of the sensors.

Examples:

• With exactly the same amount of light, the voltages at the sensors are

three volts each, regardless of the brightness: U2= U3= U1= 3 V

• If, for example, the middle sensor FT3were illuminated four times brighter

than FT2and FT1, a voltage four times lower would drop at FT3and the
supply voltage would be divided as follows: U2= 4 V, U3= 1 V, U1= 4 V

Note:

The two variable voltages between the three sensors control the speed of
the two motors.

FT

2

U

2

FT3U

3

FT

1 U1