Wednesday, February 17, 2016

Pengertian Kapasitor



Kapasitor


Sebutan populer dari kapasitor adalah kondensator, sebenarnya kata kapasitor berasal dari 
bahasa Inggris dan kondensator berasal dari bahasa Belanda. Untuk selanjutnya kita akan
menyebut kapasitor. Pada dasarnya kapasitor adalah dua keping logam yang saling berpisah
seperti pada gambar berikut ini.





















Lempeng A & B dipisahkan oleh udara atau bahan elektrik untuk mengatur nilai
kapasitansi kapasitor tersebut. Selain bahan diantara lempeng, luas penampang
dan jarak antar plat juga menentukan nilai kapasitansi kapasitor tersebut.

Pada dasarnya semua kondensator sama, yaitu terdiri dari dua logam yang terisolasi dan saling berhadapan. Diantara kedua logam diisi dengan bahan yang bermacam-macam. Nilai kapasitansi diberi nama Farad, diambil dari nama orang yang berjasa dalam pembuatan kapasitor.


Faktor-faktor yang menentukan nilai kapasitor adalah :

C = A ∈ / D

Dimana :

A => Luas penampang plat.
∈ => Bahan diantara lapisan.
D => Jarak antara kedua plat kapasitor.


Jenis-jenis kapasitor yang umum digunakan adalah :


  • mika  
  • milar  
  • kertas  
  • polyester
  • tantalum
  • keramik
  • elektrolit
  • dll

Fungsi Kapasitor

Sifat dasar kapasitor adalah untuk menyimpan muatan listrik, tentang dalam
penggunaan kapasitor digunakan untuk berbagai keperluan yaitu :

  • menahan arus dc
  • melewatkan arus dc
  • filter
  • penalaan (tuning)
  • penghubung antar tingkat (kopling)
  • penentu frekwensi
  • menghindar/meredam bunga api listrik pada saat saklar dikontrakkan

Seri dan Paralel

Untuk mendapatkan nilai kapasitor seperti yang diperlukan, maka kapasitor
dapat dihubungkan secara seri dan paralel.






Nilai total kapasitor yang dihubungkan seri akan selalu lebih kecil dari pada nilai kapasitansi
kapasitor yang paling kecil. Nilai kapasitor yang dihubungkan paralel akan selalu lebih besar
dari nilai salah satu kapasitor yang paling besar.

Cara membaca nilai kapasitansi kapasitor mirip dengan cara membaca nilai resistor, Misalnya
jika kapasitor tertulis 104 maka cara membaca nilainya adalah sbb :

Dua digit pertama adalah bilangan dan digit ketiga adalah jumlah nol dibelakang kedua digit
pertama dan satuannya adalah pikofarad.


1->  angka 1
0->  angka 0
4->  angka 0000

sehingga sama dengan 100000 pf = 100nf = 0.1 f

1 nf-100 µf
1 nf-1000 µf


Untuk jenis kapasitor yang berukuran besar seperti kapasitor elektrolit, nilainya dituliskan langsung
pada kapasitor tersebut biasanya mulai 1 f. Selain nilai kapasitansi kapasitor tersebut juga dituliskan
nilai tegangan kerja dari kapasitor, misalnya 10 V.

Jadi nilai kapasitor dibaca sebagai 1f 10V. Ini kapasitor tersebut tidak dapat dipakai pada tegangan
yang lebih tinggi dari 10 volt, jika dipakai pada tegangan kerja lebih tinggi dari 10 volt maka kapa-
sitor tersebut akan rusak. Pada umumnya kapasitor yang bernilai besar dipakai pada bagian power
supply.

Jika suatu sinyal dengan frekwensi tertentu dilewatkan melalui suatu kapasitor maka kapasitor
akan bertindak seperti suatu resistor dengan nilai hambatan sbb :

Xc = 1/(2 *F*C)

Dimana Xc disebut sebagai reaktansi kapasitif dari suatu kapasitor yang dilewati suatu sinyal, dan
F adalah frekwensi dari sinyal yang melewatkannya, serta C adalah kapasitansi kapasitor.


Sekian saya bisa menjelaskan dalam artikelnya, 
dan terima kasih telah meluangkan waktunya.

Friday, January 1, 2016

TROUBLESHOOTING D-LINK DWR-112



SETUP AND CONFIGURATION PROBLEMS










  • HOW DO I CONFIGURE MY DWR-112 3G WI-FI ROUTER WITHOUT THE INSTALLATION CD, OR CHECK MY WIRELESS NETWORK NAME (SSID) AND WIRLESS ENCRYPTION KEY ?

  • Connect your PC to the DWR-112 using an Internet cable.
  • Open a web browser and enter the router address: http://192.168.0.1
  • The default username is admin. The default password is blank (leave this box empty).
  • If you have changed the password and cannot remember it, you will need to reset the router to   factory default in order to set the password back to blank.

  • HOW DO I RESET MY DWR-112 3G WI-FI ROUTER TO FACTORY DEFAULT SETTINGS?
  •  Ensure that the DWR-112 is plugged in and receiving power.
  •  Press and hold the reset button on the front of the device for 5 seconds.
  •  Note: Resetting the product to the factory default will erase the current configuration. To    reconfigure your setting, log into the DWR-112 as outlined in question 1, then run the Setup  Wizard.



  •  HOW DO I ADD A NEW WIRELESS CLIENT OR PC IF I HAVE FORGOTTEN MY WIRELESS NETWORK NAME (SSID) OR WIRELESS ENCRYPTION KEY?

  • For each PC that needs to connect to the DWR-112 wirelessly, you must ensure that the correct Wireless Network Name (SSID) and encryption key has been entered.
  • Use the web based user interface (as described in question 1 above) to verity or choose your wireless settings.
  • Make sure you write down these setting so that you can enter them into each wirelessly connected PC. You will find a dedicated area on the back of this document to write down this important information for future use.



  •   WHY AM I UNABLE TO ESTABLISH AN INTERNET CONNECTION ?

  •   If connecting using a 3G connection, make sure that you are within range of the mobile service  provider, and that the service has been correctly configured.
  •  If connecting using the WAN via ADSL / Cable service, make sure the modem has been  enabled/connected and is operational, and that the service is correctly configured.

Belajar Tentang Arus Listrik


RESISTOR





Untuk mengendalikan arus listrik dalam sebuah rangkaian listrik, digunakan komponen yang mempunyai hambatan. Dengan perkataan lain komponen tersebut berkemampuan yang membatasi arus listrik yang mengalir, komponen tersebut disebut dengan RESISTOR dan disimbolkan dengan R.


Arus listrik bergerak dari bagian yang bertegangan yaitu lebih tinggi menuju tegangan yang lebih
rendah. Atau sering juga dikatakan arus bergerak dari positif menuju negatif.
















Untuk mengatur besar kecilnya arus yang mengalir dalam suatu rangkaian listrik, kita akan menggunakan suatu komponen yang disebut dengan RESISTOR. Yaitu suatu komponen yang
mempunyai sifat-sifat menahan penggerakan arus listrik. Arus listrik diberikan dengan simbol
I dan besarnya arus disebut dengan Ampere atau amp dan sering hanya satu huruf A. Resistansi
suatu resistor disingkat dengan huruf R dan nilai hambatannya disebut dengan ohm atau Ω.
Tegangan listrik disebut Volt dan disingkat dengan huruf V.

Gabungan ketiga besaran listrik disebut dapat dilihat pada gambar dibawah ini :









Tegangan (Volt) = Arus(Ampere) x Hambatan Ω (Ohm)

V = I x R


Arus adalah gerakan muatan negatif (elektron) dan hanya dapat bergerak bebas pada bahan-bahan
logam. Arus dapat bergerak karena adanya beda tegangan pada dua titik pada penghantar. Arus
hanya dapat mengalir pada suatu rangkaian tertutup, artinya harus dihubungkan ke kutup positif
dan kutup negatif.

BIPOLAR TRANSISTORS




Transistors are three terminal active devices made from different semiconductor materials that can act as either an insulator or a conductor by the application of a small signal voltage. The transistor’s ability to change between these two states enables it to have two basic functions: “switching” (digital electronics) or “amplification” (analogue electronics). Then Bipolar Transistors have the ability to operate within three different regions:



  • • Active Region   –   the transistor operates as an amplifier and Ic = β.Ib
  • • Saturation   –   the transistor is “Fully-ON” operating as a switch and Ic = I(saturation)
  • • Cut-off   –   the transistor is “Fully-OFF” operating as a switch and Ic = 0

The word Transistor is an acronym, and is a combination of the wordsTransfer Varistor used to describe their mode of operation way back in their early days of development. There are two basic types of bipolar transistor construction, PNP and NPN, which basically describes the physical arrangement of the P-type and N-type semiconductor materials from which they are made.


The Bipolar Transistor basic construction consists of two PN-junctions producing three connecting terminals with each terminal being given a name to identify it from the other two. These three terminals are known and labelled as the Emitter ( E ), the Base ( B ) and the Collector ( C ) respectively.










Bipolar Transistors are current regulating devices that control the amount of current flowing through them in proportion to the amount of biasing voltage applied to their base terminal acting like a current-controlled switch. The principle of operation of the two transistor types PNP and NPN, is exactly the same the only difference being in their biasing and the polarity of the power supply for each type.

Bipolar Transistor Construction


1. PNP Transistor





2.NPN Transistor






The construction and circuit symbols for both the PNP and NPN bipolar transistor are given above with the arrow in the circuit symbol always showing the direction of “conventional current flow” between the base terminal and its emitter terminal. The direction of the arrow always points from the positive P-type region to the negative N-type region for both transistor types, exactly the same as for the standard diode symbol.



Bipolar Transistor Configurations


As the Bipolar Transistor is a three terminal device, there are basically three possible ways to connect it within an electronic circuit with one terminal being common to both the input and output. Each method of connection responding differently to its input signal within a circuit as the static characteristics of the transistor vary with each circuit arrangement.


  • • Common Base Configuration   –   has Voltage Gain but no Current Gain.
  • • Common Emitter Configuration   –   has both Current and Voltage Gain.
  • • Common Collector Configuration   –   has Current Gain but no Voltage Gain.

The Common Base (CB) Configurations


As its name suggests, in the Common Base or grounded base configuration, the BASE connection is common to both the input signal AND the output signal with the input signal being applied between the base and the emitter terminals. The corresponding output signal is taken from between the base and the collector terminals as shown with the base terminal grounded or connected to a fixed reference voltage point.
The input current flowing into the emitter is quite large as its the sum of both the base current and collector current respectively therefore, the collector current output is less than the emitter current input resulting in a current gain for this type of circuit of “1” (unity) or less, in other words the common base configuration “attenuates” the input signal.

The Common Base Transistor Circuit





This type of amplifier configuration is a non-inverting voltage amplifier circuit, in that the signal voltages Vin and Vout are “in-phase”. This type of transistor arrangement is not very common due to its unusually high voltage gain characteristics. Its input characteristics represent that of a forward biased diode while the output characteristics represent that of an illuminated photo-diode.
Also this type of bipolar transistor configuration has a high ratio of output to input resistance or more importantly “load” resistance ( RL ) to “input” resistance ( Rin ) giving it a value of “Resistance Gain”. Then the voltage gain ( Av ) for a common base configuration is therefore given as:

Commbon Base Voltage Gain



Where: Ic/Ie is the current gain, alpha ( α ) and RL/Rin is the resistance gain.
The common base circuit is generally only used in single stage amplifier circuits such as microphone pre-amplifier or radio frequency ( Rf ) amplifiers due to its very good high frequency response.

The Commbon Emitter (CE) Configuration


In the Common Emitter or grounded emitter configuration, the input signal is applied between the base and the emitter, while the output is taken from between the collector and the emitter as shown. This type of configuration is the most commonly used circuit for transistor based amplifiers and which represents the “normal” method of bipolar transistor connection.
The common emitter amplifier configuration produces the highest current and power gain of all the three bipolar transistor configurations. This is mainly because the input impedance is LOW as it is connected to a forward biased PN-junction, while the output impedance is HIGH as it is taken from a reverse biased PN-junction.

The Commbon Emitter Amplifier Circuit





In this type of configuration, the current flowing out of the transistor must be equal to the currents flowing into the transistor as the emitter current is given as Ie = Ic + Ib.

As the load resistance ( RL ) is connected in series with the collector, the current gain of the common emitter transistor configuration is quite large as it is the ratio of Ic/Ib. A transistors current gain is given the Greek symbol of Beta, ( β ).
As the emitter current for a common emitter configuration is defined as Ie = Ic + Ib, the ratio of Ic/Ie is called Alpha, given the Greek symbol of α. Note: that the value of Alpha will always be less than unity.
Since the electrical relationship between these three currents, IbIcand Ie is determined by the physical construction of the transistor itself, any small change in the base current ( Ib ), will result in a much larger change in the collector current ( Ic ).
Then, small changes in current flowing in the base will thus control the current in the emitter-collector circuit. Typically, Beta has a value between 20 and 200 for most general purpose transistors. So if a transistor has a Beta value of say 100, then one electron will flow from the base terminal for every 100 electrons flowing between the emitter-collector terminal.
By combining the expressions for both Alphaα and Betaβ the mathematical relationship between these parameters and therefore the current gain of the transistor can be given as:





Where: “Ic” is the current flowing into the collector terminal, “Ib” is the current flowing into the base terminal and “Ie” is the current flowing out of the emitter terminal.
Then to summarise a little. This type of bipolar transistor configuration has a greater input impedance, current and power gain than that of the common base configuration but its voltage gain is much lower. The common emitter configuration is an inverting amplifier circuit. This means that the resulting output signal is 180o “out-of-phase” with the input voltage signal.

The Commbon Collector (CC) Configuration


In the Common Collector or grounded collector configuration, the collector is now common through the supply. The input signal is connected directly to the base, while the output is taken from the emitter load as shown. This type of configuration is commonly known as a Voltage Follower or Emitter Follower circuit.
The common collector, or emitter follower configuration is very useful for impedance matching applications because of the very high input impedance, in the region of hundreds of thousands of Ohms while having a relatively low output impedance.

The Commbon Collector Transistor Circuit





The common emitter configuration has a current gain approximately equal to the β value of the transistor itself. In the common collector configuration the load resistance is situated in series with the emitter so its current is equal to that of the emitter current.
As the emitter current is the combination of the collector AND the base current combined, the load resistance in this type of transistor configuration also has both the collector current and the input current of the base flowing through it. Then the current gain of the circuit is given as:

The Commbon Collector Current Gain




This type of bipolar transistor configuration is a non-inverting circuit in that the signal voltages ofVin and Vout are “in-phase”. It has a voltage gain that is always less than “1” (unity). The load resistance of the common collector transistor receives both the base and collector currents giving a large current gain (as with the common emitter configuration) therefore, providing good current amplification with very little voltage gain.
We can now summarise the various relationships between the transistors individual DC currents flowing through each leg and its DC current gains given above in the following table.

Relationship Between DC Current And Gain





Bipolar Transistor Summary

Then to summarise, the behaviour of the bipolar transistor in each one of the above circuit configurations is very different and produces different circuit characteristics with regards to input impedance, output impedance and gain whether this is voltage gain, current gain or power gain and this is summarised in the table below.


Bipolar Transistor configurations






with the generalised characteristics of the different transistor configurations given in the following table:









In the next tutorial about Bipolar Transistors, we will look at the NPN Transistor in more detail when used in the common emitter configuration as an amplifier as this is the most widely used configuration due to its flexibility and high gain. We will also plot the output characteristics curves commonly associated with amplifier circuits as a function of the collector current to the base current.


So that I can say and thanks.