Power Supply; Additional Sensors; The Robot Models; The Basic Model - fischertechnik Mobile Robots II Manual De Instrucciones

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power is generated, which results in displacement of the conductor in the
magnetic field. The rotor moves. The simple conductor loop is designed as a
coil for practical applications (with or without iron core for amplifying the
The construction kit contains two different motor types: the mini motor and
the power motor. The small, compact mini motor with worm is designed for
auxiliary drive or special purposes with small power requirements. It always
requires gears for reducing rotational speed.
The power motor provides much larger torque. It has fixed, flanged gears
with a reduction ratio of 50:1. Consequently, it is ideal for the drive
requirements for our robot. But it also exists in a variant with a reduction
ratio of 8:1 (not contained in this construction kit). But the rotational speed
would be too great on the drive shaft for the robot drive.

3.5 Power Supply

Mobile systems require an autonomous power supply. All energy users
Accumulators are preferable to normal batteries, because they can be
recharged many times. The fischertechnik Accu Set provides a good
compromise between energy supply and size. The Accu Set is not a
component of this construction kit. It can be purchased together with a
special charger as an "Accu Set" with article number 34969. The switching
symbol and the accumulator are displayed in the drawing. In a normal
case, the polarity is not shown in a switching symbol. You can remember
more easily which connection is plus using this simple example: "You can cut
through the long line and make it a plus."
It is very important to pay attention to correct polarity when you connect
voltage sources.
20
magnetic field). Very many direct current motors
generate the required magnetic field using permanent
magnets, which are stuck into the metal coating of the
stator. Current is fed to a rotating rotor using sliding
contacts. These contacts provide the current direction
reversal in the conductor loop at the same time, which
is necessary for uninterrupted rotational movement.
The rotational speed of normal motors is in the range of
a few thousand revolutions per minute. Gears provide
for lower rotational speeds with large torque.
are supplied from this energy source. The power
supply requirements differ. While drive motors are
content with destabilized voltages, many sensors
require stable voltages to provide precise results.
For economic reasons, the use of batteries or accumu-
lators is the only meaningful way to supply robots
with current. Solar cells or fuel cells are unfortunately
not sufficiently powerful to provide practical results
with a reasonable amount of expense.

3.6 Additional Sensors

The fischertechnik system can be expanded relatively easily with additional
sensors. In the simplest case, we can use sensors from other kits, e.g., the
thermal sensor or the magnetic sensor from the "Profi Sensoric" construction
kit, article no. 30491.
But we can also use completely different sensors. Very different kits and
components are for sale in specialized stores. Even exotic sensors such as
gas detectors or radar sensors can be used. But because we do not want to
destroy the Intelligent Interface with high input voltages or incorrect loads,
only experienced do-it-yourselfers should create their own solutions. The
most reliable way to connect additional sensors is to separate sensor and
interface galvanically. A number of sensors have a relay, which is well suited
for this. The switching contacts of the relay are connected like a customary
fischertechnik switch and then signal the occurrence of new environmental
stimuli. Tip: Such expanded experiments are published by enthusiastic
"fischer technicians" in the Internet.
4 Robot Models
A few variants of mobile, autonomous robots are presented in the following
construction suggestions. We'll start with a simple model. Based on that,
you can use your imagination and try using different sensors. Here is it a
question of linking both the internal states of the robot, e.g., distance
measurement by impetus wheels, and the external environmental signals
such as light or searching for lanes. Then specific tasks are set for each
model. They are designed to stimulate your imagination and make you
familiar with the material. The LLWin programs for the individual tasks are
on the CD-ROM, which is included in the construction kit. But try to think up
your own tasks for the models. The simplest model is the basic model. The
drive motors are assembled with the interface to create a compact unit with
it. Two motors provide the drive power of the robot. They are arranged
opposite each other, so that each motor runs a drive wheel. A support
wheel provides stability, so that this robot does not tip over. Such an
arrangement of the motors is called differential drive. It provides the highest
degree of mobility with the minimally required movement space. Turning in
place is even possible. But the center point of both motors is the center of
rotation around which the robot moves. In this way, it is able to navigate in
the most difficult situations with little computing work.
The motors can drive the wheels via two different gear reductions (slow
100:1 or fast 50:1). For the slower variant, the drive is reduced additionally
at a ratio of 2:1 using fischertechnik toothed gears. Which gear reduction is
used is indicated for the models.

4.1 The Basic Model

Let's build the basic model (gear reduction 100:1) first in accordance with
the construction instructions. Because this model serves as a basis for many
experiments, proceed very carefully when assembling it. After all mechanical
components have been assembled, check the soft running of the motors.
Each motor is connected directly with the accumulator without the interface
for this.