This is a short tutorial from a series of small
tutorials on basic electronics for robotics.
Basically it covers the basics you need to know to start learning
robotics. I am not covering topics usually covered in the usual beginner
textbooks for example the atom, charge, electric fields, electrostatics etc

To have a basic electronic circuit we need to
have a power source usually a battery, a path i.e. the wires and a load i.e. a
motor, bulb etc.

For mobile robots and mains power for
stationary such as industrial robots. Imagine the power source as the beginning
of the electricity and the end of its journey.
The electricity starts its journey from the positive of the battery
passes through a path do it’s job for example light a bulb, or turn a motor and
return to the negative of the battery. I
recommend to read the admin tutorial on batteries because it is very
informative.

This is bit theoretic but assume that
electricity needs a force in order to flow from the positive to negative. This force is called voltage and is measured
in volts (V). I suppose you have heard of 9 volts batteries and 115/230 volt
main electricity. By nature voltage
creates a force when applied to a load through a path it forces the particles
of that path to move or flow, this flow of particles of better the electrons is
called the current which is measured in amps (A). The more the voltage the more the current,
and this fact is known as ohms law which states that current passing through a
path (conductor) is directly proportional to the voltage applied. Which mean
that doubling the voltage will double the current and reducing the voltage will
reduce the current. Skipping mathematics we know that voltage is directly
proportional to current, to form an equation we need a constant and this
constant is called resistance which Is measured in Ohms , this is the
opposition to current thus we can conclude that voltage is equal to current x
resistance or V=IR.

Another rule called Kirchhoff’s voltage law
tells us that all voltage must be distributed among the load thus if we have
two identical loads and applied a 10 V voltage we except to have a 5V on each
load.

Kirchhoff also told use that if the circuit has
one path the current is the same everywhere in the circuit

An example we have a 9 volt battery and
connected to it is a heating element (which is basically a resistance) of 9
ohms we can re arrange the formula to find the current. So Current = V/R = 9/9 = 1 Amp

Another useful example is to calculate the
resistor that is needed for an L.E.D. We
know that L.E.Ds for some reason do not obey ohms law and usually have a
voltage drop of around 2V and can sustain a current of 0.02 A or 20mA.. We now these facts, that all the voltage must
be dropped thus if the L.E.D drops 2 volts and we applied 9v we know that the
resistor has 7 volts applied on it, we also know that in a series circuit the
current is equal everywhere in the circuit thus if we want a current of 20mA to flow in
the circuit. We know that resistor obey
ohms law thus the current flowing through it is (9-2)/0.02 = 350 ohms. Thus if
we connect a 350 ohm resistor to an LED with a 9v battery we know that the
current flowing through the LED is 20mA which is a safe current for an LED to
operate.

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To start this topic we should know the basic definition of a
sensor, a sensor is a device that converts real world quantities such as
temperature and light into electrical signals, these signals can be either
analog or digital. A signal is an electrical quantity such as voltage that
changes over time.

Just for teaching purpose we can assume we are using 5 volt
supply, this is just an arbitrary value and nothing special about it, so the
voltage cannot get higher than 5. An
analog signal can take any value between 0 and 5 so 0.00000002, 4.998, 3.51,
1.56, 0.5 are all valid values, assuming we are reading temperature, the
temperature is no just 32 C/F but in reality it is 32.something. So analog
signal are precise but unfortunately computers cannot process any value but
only discreet values call digital signals

A graph of analog (black) versus digital (yellow) is found attached

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analog vs digital.png | 37.2 KB |