EL TRATAMIENTO ACTUAL DEL PRINCIPIO DE CONFIANZA
1. Sólo puede confiar quien se ha comportado correctamente
The concept of an electronic dog color is using low dc voltage (3Vdc) to generate a high
controllable dc voltage (1000dc). There are many ways to do it.
Solution 1
3Vdc > Inverter > Multiplier > 1000Vdc
Solution 2
3Vdc > Inverter (using microcontroller) > Transformer > Multiplier > 1000Vdc
Solution 3
3Vdc > Inverter > Transformer > converter > 1000Vdc
Solution 4
3Vdc > Inverter >Transformer > Multiplier > 1000Vdc (Preferred)
In this project, transformer and multiplier (solution 4) are going to use. Before talking the idea
of electronic dog color, that is one important thing that have to mention which is the form of
64 4.1.1 Inverter
An inverter is an electrical or electro-mechanical device that converts direct current (DC) to
alternating current (AC); the resulting AC can be at any required voltage and frequency with the
use of appropriate transformers, switching, and control circuits. Static inverters have no moving
parts and are used in a wide range of applications, from small switching power supplies in
computers, to large electric utility high-voltage direct current applications that transport bulk
power. Inverters are commonly used to supply AC power from DC sources such as solar panels
or batteries. The electrical inverter is a high-power electronic oscillator. It is so named because
early mechanical AC to DC converters was made to work in reverse, and thus was "inverted", to
convert DC to AC. The inverter performs the opposite function of a rectifier.
Inverter is important component in this project; this is because any step-up or step-down
voltage component the input must in ac form, in example transformer and multiplier. There are
many type of inverter, in example like current-source inverters, variable dc-link inverter, boost
inverter and buck-boost inverter. In this project, transistor (BJT) is chosen as inverter
(oscillator) so that can activate transformer for step-up voltage purpose.
65 4.1.2 Transformer
A transformer is a device that transfers electrical energy from one circuit to another through
inductively coupled conductors — the transformer's coils or "windings". Except for air-core
transformers, the conductors are commonly wound around a single iron-rich core, or around
separate but magnetically-coupled cores. A varying current in the first or "primary" winding
creates a varying magnetic field in the core (or cores) of the transformer. This varying magnetic
field induces a varying electromotive force (EMF) or "voltage" in the "secondary" winding. This
effect is called mutual induction. If a load is connected to the secondary, an electric current will
flow in the secondary winding and electrical energy will flow from the primary circuit through
the transformer to the load. In an ideal transformer, the induced voltage in the secondary
winding (VS) is in proportion to the primary voltage (VP), and is given by the ratio of the number
of turns in the secondary to the number of turns in the primary as follows:
By appropriate selection of the ratio of turns, a transformer thus allows an alternating current
(AC) voltage to be "stepped up" by making NS greater than NP, or "stepped down" by making NS
less than NP. Transformers come in a range of sizes from a thumbnail-sized coupling
transformer hidden inside a stage microphone to huge units weighing hundreds of tons used to
interconnect portions of national power grids. All operate with the same basic principles,
although the range of designs is wide. While new technologies have eliminated the need for
transformers in some electronic circuits, transformers are still found in nearly all electronic
devices designed for household ("mains") voltage. Transformers are essential for high voltage
66 The transformer is based on two principles: firstly, that an electric current can produce a
magnetic field (electromagnetism) and secondly that a changing magnetic field within a coil of
wire induces a voltage across the ends of the coil (electromagnetic induction). Changing the
current in the primary coil changes the magnitude of the applied magnetic field. The changing
magnetic flux extends to the secondary coil where a voltage is induced across its ends.
Figure 4.2: An ideal step-down transformer showing magnetic flux in the core.
A simplified transformer design is shown above. A current passing through the primary coil
creates a magnetic field. The primary and secondary coils are wrapped around a core of very
high magnetic permeability, such as iron; this ensures that most of the magnetic field lines
produced by the primary current are within the iron and pass through the secondary coil as well
67 4.1.3 Induction law
The voltage induced across the secondary coil may be calculated from Faraday's law of
induction, which states that:
Where VS is the instantaneous voltage, NS is the number of turns in the secondary coil and Φ
equals the magnetic flux through one turn of the coil. If the turns of the coil are oriented
perpendicular to the magnetic field lines, the flux is the product of the magnetic field strength B
and the area A through which it cuts. The area is constant, being equal to the cross-sectional
area of the transformer core, whereas the magnetic field varies with time according to the
excitation of the primary. Since the same magnetic flux passes through both the primary and
secondary coils in an ideal transformer, the instantaneous voltage across the primary winding
equals
Taking the ratio of the two equations for VS and VP gives the basic equation for stepping up or
68 4.1.4 Ideal power equation
Figure 4.3: The ideal transformer as a circuit element
If the secondary coil is attached to a load that allows current to flow, electrical power is
transmitted from the primary circuit to the secondary circuit. Ideally, the transformer is
perfectly efficient; all the incoming energy is transformed from the primary circuit to the
magnetic field and into the secondary circuit. If this condition is met, the incoming electric
power must equal the outgoing power.
Pincoming = IPVP = Poutgoing = ISVS
Giving the ideal transformer equation
If the voltage is increased (stepped up) (VS > VP), then the current is decreased (stepped
down) (IS < IP) by the same factor. Transformers are efficient so this formula is a reasonable
69 The impedance in one circuit is transformed by the square of the turns ratio. For example, if an
impedance ZS is attached across the terminals of the secondary coil, it appears to the primary
circuit to have an impedance of . This relationship is reciprocal, so that the
impedance ZP of the primary circuit appears to the secondary to be .
4.1.5 Weakness of transformer in this project
Even though transformer can step-up voltage but the output are depend to the turn ratio,
which is fix by manufacture. This weakness cause the output dc voltage cannot be controllable
to reach desire voltage level. To overcome this problem voltage multiplier is selected.
From frequency view point, transformer cannot work in low frequency range this is because, if
the rate of cutting magnetic flux too slows (low frequency) transformer cannot be drive.
(Voltage is direct proportional to frequency)
4.1.6 Voltage multiplier
A voltage multiplier is an electrical circuit that converts AC electrical power from a lower voltage
to a higher DC voltage by means of capacitors and diodes combined into a network. Voltage
multipliers can be used to generate bias voltages of a few volts or tens of volts or millions of
volts for purposes such as high-energy physics experiments and lightning safety testing. The
most common type of voltage multiplier is the half-wave series multiplier, also called the Villard
70 Figure 4.4: Villard cascade voltage multiplier.
Voltage multiplier can multiply the input ac voltage to output dc voltage by any integer number
like 1, 2, 3, 4…..by changing the arrangement of diode-capacitor pair (Shown in Figure 1 to 4
below)
71 Figure 4.6: Output dc voltage is 2 times Vin (input ac voltage)
72 Figure 4.8: Output dc voltage is 4 times Vin (input ac voltage)
By changing the diode-capacitor pair, the level of output dc voltage can be step-up.
4.1.7 Weakness of voltage multiplier
Voltage multiplier only step-up voltage to any higher level voltage (controllable), but still cannot
get desire output dc voltage level unless using voltage divider method. From frequency view
point, voltage multiplier cannot work in high frequency range this is because charging time of
capacitor cannot too short (high frequency).
4.1.8 Overview of project (electronic dog collar)
Inverter = dc to ac
Transformer =ac to ac
73 Figure 4.9: Overview of Electronic dog collar