Assalamualaikum..
Have a nice day..
This week, I have to study some of the components that I have bought last week.
After doing the researched about all the components,
this is all the information that I've got.
This is the circuit that is flexible enough to cater for many different applications.
Application for basic circuit includes switching on a porch lamp at dusk,
briefly sounding the buzzer when someone’s shadow falls on the sensor.
With the addition of second circuit board,
there is an optional extra stage to this project, called Differentiator.
This changes the response of the trigger with the differentiator incorporated into the circuit.
It is unaffected if light levels change slowly
but shows a sharp change in output when the level change rapidly.
MEL 12 PHOTOTRANSISTOR
This is very sensitive device incorporating an amplifying circuit in the form of a Darlington pair.
However we do not make connection to the base in this trigger circuit
because the light energy falling on the phototransistor generates the equivalent of a small base current.
This is amplified within the device
to produce a collector emitter current in the region of 3mA in bright light.
Although ordinary transistors exhibit the photosensitive effects if they are exposed to light,
the structure of the phototransistor is specifically optimized for photo applications.
The phototransistor has much larger base and collector areas than would be used for a normal transistor. These devices were generally made using diffusion or ion implantation.
Early phototransistors used germanium or silicon throughout the device giving a homo-junction structure.
The more modern phototransistors use type III-V materials such as gallium arsenide.
Hetero structures that use different materials either side of the p-n junction are also popular
because they provide a high conversion efficiency.
These are generally fabricated using epitaxial growth of materials that have matching lattice structures.
These photo transistors generally use a mesa structure.
Sometimes a Schottky (metal semiconductor) junction can be used
for the collector within a phototransistor,
although this practice is less common these days
because other structures offer better levels of performance.
RESISTOR
A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element.
The current through a resistor is in direct proportion to the voltage across the resistor's terminals.
This relationship is represented by Ohm's law.
The electrical functionality of a resistor is specified by its resistance:
common commercial resistors are manufactured
over a range of more than nine orders of magnitude.
When specifying that resistance in an electronic design,
the required precision of the resistance may require attention
to the manufacturing tolerance of the chosen resistor, according to its specific application.
The temperature coefficient of the resistance may also be of concern in some precision applications.
POTENTIOMETER
Potentiometers comprise a resistive element,
a sliding contact (wiper) that moves along the element,
making good electrical contact with one part of it,
electrical terminals at each end of the element,
a mechanism that moves the wiper from one end to the other,
and a housing containing the element and wiper.
Many inexpensive potentiometers are constructed
with a resistive element formed into an arc of a circle
usually a little less than a full turn, and a wiper rotating around the arc and contacting it.
The resistive element, with a terminal at each end, is flat or angled.
The wiper is connected to a third terminal, usually between the other two.
On panel potentiometers, the wiper is usually the center terminal of three.
For single-turn potentiometers,
this wiper typically travels just under one revolution around the contact.
The only point of ingress for contamination is the narrow space
between the shaft and the housing it rotates in.
Another type is the linear slider potentiometer,
which has a wiper which slides along a linear element instead of rotating.
Contamination can potentially enter anywhere along the slot the slider moves in,
making effective sealing more difficult and compromising long-term reliability.
An advantage of the slider potentiometer is that the slider position gives a visual indication of its setting.
While the setting of a rotary potentiometer can be seen by the position of a marking on the knob,
an array of sliders can give a visual impression of.
VN10KM n-channel Mosfet
A mosfet is used for intensifying or swapping electronic signals since it a semiconductor gadget.
It has three terminals, the collector, the emitter, and the base.
In which current in the base terminal
is used to control the flow of current between the emitter and the collector.
It is by far the most common transistor in both digital and analog circuits.
Enhancement-mode MOSFET operates using a positive input voltage
and has an extremely high input resistance (almost infinite)
making it possible to interface with nearly any logic gate or driver capable
of producing a positive output.
Also, due to this very high input (Gate) resistance
we can parallel together many different MOSFETs
until we achieve the current handling limit required.
While connecting together various MOSFETs may enable us to switch high currents or high voltage loads, doing so becomes expensive and impractical in both components and circuit board space.
To overcome this problem Power Field Effect Transistors or Power FET's were developed.
MOSFETs are voltage-controlled power devices.
If no positive voltage is applied between gate and source
the MOSFET is always non-conducting.
If we apply a positive voltage UGS to the gate
we'll set up an electrostatic field between it and the rest of the transistor.
The positive gate voltage will push away the 'holes' inside the p-type substrate and attracts the moveable electrons in the n-type regions under the source and drain electrodes.
This produces a layer just under the gate's insulator through which electrons can get into and move along from source to drain.
The positive gate voltage therefore 'creates' a channel
in the top layer of material between oxide and p-Si.
Increasing the value of the positive gate voltage pushes
the p-type holes further away and enlarges the thickness of the created channel.
As a result we find that the size of the channel
we've made increases with the size of the gate voltage and enhances
or increases the amount of current which can go from source to drain-
this is why this kind of transistor is called an enhancement mode device.
So, from the research,
I've been able to explaining and knowing detailed about components that will be used in project.
Tomorrow, I'll continue with another components overview and informations.
With this informations, I can gain my knowledge in exploring all the electronics components advantages me in present and future.
Wassalam.
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