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6/30/2011

APLIKASI MIKROKONTROLER ATMEGA8535 SEBAGAI PEMBANGKIT PWM SINUSOIDA 1 FASA UNTUK MENGENDALIKAN PUTARAN MOTOR SINKRON

ABSTRACT

Single phase pulse width modulation inverter is a circuit which convert DC voltage to AC voltage for one phase. Generating PWM signal digitally give good performance because their immune from noisy. Designing a PWM signal generator using microcontroller has several advantages, such as easy to programmed and network inverter become modestly. The aim of this thesis is designing generating of signal PWM one phase by using microcontroller ATMEGA8535. By using this inverter, hence operation of speed of motor AC can be controlled with more carefully. This network inverter is designed so that summarize, therefore a minimum system of microcontroller only rely on the single chip mode.
Observation shows that the design of PWM generator work well. The PWM signal which produced has
24 pulse each period and frequency interval between 20 – 60 Hz with the increase and degradation of each every 1 Hz.
ABSTRAKSI

Pulse Width Modulation Inverter satu fase adalah rangkaian pengubah tegangan searah menjadi tegangan bolak balik untuk satu fase. Pembangkitan sinyal PWM secara digital dapat memberikan unjuk kerja sistem yang bagus karena lebih kebal terhadap gangguan/derau. Perancangan sebuah pembangkit sinyal PWM menggunakan mikrokontroler memiliki beberapa keuntungan yaitu mudah diprogram dan rangkaian inverter menjadi sederhana. Tujuan tugas akhir ini adalah merancang pembangkit sinyal PWM satu fase dengan menggunakan mikrokontroler ATMEGA8535. Dengan menggunakan inverter ini, maka pengendalian kecepatan motor AC dapat dilakukan dengan lebih teliti. Rangkaian inverter ini dirancang supaya ringkas, oleh karena itu pada sistem minimal mikrokontroler hanya mengandalkan ragam chip tunggal.
Hasil pengamatan menunjukan bahwa rancangan pembangkit PWM telah berfungsi dengan baik. Sinyal PWM yang dibangkitkan memiliki 24 pulsa setiap periode dan rentang frekuensi antara 20 – 60 Hz dengan kenaikan dan penurunan setiap 1 Hz.


I.Pendahuluan
Motor AC memiliki keunggulan dalam hal kesederhanaan dan murahnya biaya perawatan sehingga jenis motor ini banyak dipakai di lingkungan industri maupun rumah tangga. Pengendalian kecepatan putaran motor AC dapat dilakukan dengan beberapa cara diantaranya dengan kendali tegangan dan frekuensi.
Inverter adalah konverter DC ke AC
dengan tegangan dan frekuensi keluaran dapat diatur sehingga motor AC dapat dikendalikan dengan fleksibel. Ada beberapa jenis inverter diantaranya adalah inverter PWM (Pulse Width Modulation). Keuntungan operasi inverter PWM sebagai teknik konversi dibanding dengan jenisjenis inverter lainnya adalah rendahnya distorsi harmonik pada tegangan keluaran dibanding dengan jenis inverter lainnya. Selain itu teknik PWM sangat praktis dan ekonomis untuk diterapkan berkat semakin pesatnya perkembangan komponen semikonduktor (terutama komponen daya yang mempunyai waktu penyaklaran sangat cepat) Pada pengendalian kecepatan motor AC, inverter PWM mempunyai kelebihan yaitu mampu menggerakkan motor induksi dengan putaran halus dan rentang yang lebar.

Selain itu apabila pembangkitan sinyal PWM dilakukan secara digital akan dapat diperoleh unjuk kerja system yang bagus karena lebih kebal terhadap derau.

II.Tinjauan pustaka
Motor induksi pada dasarnya dapat mempunyai kecepatan yang beragam dengan cara (1) mengubah frekuensi sumber daya, (2) mengubah tegangan terminal, (3) mengubah jumlah kutubnya.
Pengaturan kecepatan putar motor induksi secara konvensional dengan mengubah jumlah kutub yaitu membagi belitan stator menjadi beberapa bagian yang sama dan menghubungkannya dengan saklar penghubung yang menentukan hubungan jumlah kutubnya. Kelemahannya, hasil pengaturan kecepatannya bertingkat tidak kontinyu, dengan dua atau lebih tingkat kecepatan. Motor dengan hubungan seperti ini biasa disebut motor Dahlander.
Pengaturan kecepatan putar motor induksi konvensional lainnya ialah mengubah nilai tegangan stator, dilakukan dengan menggunakan reaktor atau variac. Cara ini mengubah torsi motor induksi yang menyebabkan perubahan kecepatan, tetapi efisiensinya menurun tajam yang membuat metoda ini tidak banyak dipakai. Metoda ini digunakan untuk mengurangi arus awal motor induksi berdaya besar.
Pengaturan kecepatan putar motor induksi dengan mengubah frekuensi sumber tegangan pada stator dapat menghasilkan pengaturan lebih baik dibanding dengan dua metoda lainnya. Kecepatan motor lebih halus, tetapi sangat rumit dalam rangkaian pengaturannya. Konsep dasar pengubah frekuensi adalah mengubah sumber daya AC menjadi DC melalui penyearah yang dikontrol atau tidak, dan kemudian diubah kembali menjadi AC untuk memberi tegangan pada motor, yang dapat diatur besar tegangan dan frekuensinya.
Untuk mengkonversi sumber daya DC ke AC dengan tegangan dan frekuensi yang dapat diatur menggunakan salah satu cara yaitu mengatur lebar pulsa modulasi atau PWM (pulsa-width-modulation). Bentuk gelombang tegangan keluaran idealnya sinusoida, akan tetapi dalam prakteknya tidak sinusoidal dan mengandung komponen harmonik. Untuk aplikasi daya sedang dan rendah, bentuk gelombang tegangan masih berbentuk kotak yang masih dapat diterima, tetapi untuk aplikasi daya besar dibutuhkan bentuk gelombang tegangan sinusoida yang distorsinya rendah. Untuk mengurangi komponen harmonik tegangan keluaran dapat digunakan komponen switching yang cepat.
Pada tugas akhir ini menggunakan mikrokontroler dengan metoda PWM dalam sistem pengaturan kecepatan putar motor induksi satu fasa untuk memberikan keuntungan pada ketelitian sistem dan memungkinkan melakukan modifikasi atas sistem yang sudah ada hanya dengan mengganti atau mengubah perangkat lunaknya. Dengan memperhatikan keunggulan mikrokontroler dalam sistem pengaturan kecepatan putar motor induksi akan dapat mengurangi tingkat kerumitan.

III.Dasar Teori
Inverter PWM Sinusoida satu fase menghasilkan pulsa PWM bolak balik satu fase dengan nilai tegangan bolak balik efektifnya dirumuskan sebagai berikut:


   Vrms = tegangan efektif
    v = fungsi tegangan
 T = perioda

Oleh karena pada inverter SPWM nilai tegangan masukan DC adalah konstan maka tegangan rms dapat juga dirumuskan :

Vrms = tegangan efektif
VDC = tegangan searah inverter
 tp = lebar pulsa tinggi dalam 1 periode
T = perioda

Untuk menghasilkan sinyal PWM tersebut dapat menggunakan 2 buah sinyal sinus dan 1 sinyal segitiga atau dengan menggunakan 1 buah sinyal sinus dan 2 buah sinyal segitiga. Pada proses pembangkitan SPWM dengan menggunakan 2 buah sinyal sinus dan sebuah sinyal segitiga, dilakukan pembandingan amplitudo antara sinyal segitiga dengan sinyal sinus. Sinyal penggerak akan dibangkitkan apabila amplitude sinyal sinus lebih besar daripada amplitudo sinyal segitiga. Masing- masing sinyal penggerak digunakan untuk penyaklaran sehingga diperoleh sinyal PWM. Proses pembangkitan SPWM tersebut dapat dilihat pada gambar 1.

Gambar 1. (a) Proses pembandingan antara sinyal pembawa dengan sinyal referensi, (b) Sinyal penggerak VAN, (c) Sinyal penggerak VBN, (d) Sinyal SPWM

Proses pembangkitan SPWM secara digital dapat dilakukan dengan 2 cara, yaitu:
1. Dengan membangkitkan gelombang segitiga dan gelombang sinus secara diskret dengan metode look up table. Kemudian dilakukan pembandingan untuk masing-masing nilai amplitudo gelombang sinus dan segitiga seperti pada gambar 1. Cara ini sama halnya dengan membangkitkan gelombang sinus analog dan gelombang segitiga analog secara digital.

2.Dengan mencari terlebih dahulu waktu untuk setiap pulsa masing-masing sinyal penggerak, untuk dijadikan data dalam proses pembangkitan sinyal penggerak secara look up table. Cara inilah yang dipakai dalam perancangan tugas akhir ini.

IV.Metodologi Penelitian
Metodologi yang digunakan dalam penelitian ini adalah sebagai berikut :
1. Studi literatur mengenai Inverter PWM satu fase dan Mikrokontroler ATMEGA8535.
2.Merancang dan mensimulasi PWM Satu Fase secara software dengan simulink dari MATLAB 7
3.Merancang dan membuat sistem secara hardware.
4.Merancang perangkat lunak pembangkit sinyal penggerak dengan menggunakan bahasa Assembly.
5.Menguji dan mengambil data dari perancangan.
6.Menganalisa hasil dan membuat kesimpulan.

V.Hasil Implementasi dan Pembahasan
A.Perancangan Sistem
Secara lebih detailnya sistem pengendalian kecepatan motor sinkron dapat dilihat dalam gambar 2.

Gambar 2. Diagram blok secara detail

B.Untai H-Bridge
Rangkaian H-bridge berfungsi sebagai rangkaian penyaklar tegangan sekitar 50 VDC. Untuk melakukan penyaklaran, diperlukan MOSFET atau IGBT, dalam perancangan tugas akhir ini menggunakan Modul IGBT. Jenis IGBT yang digunakan pada tugas akhir ini adalah 6MBI30L-060 keluaran dari FUJI ELECTRIC, memiliki waktu naik dan turun yang cepat, dengan tegangan kolektor-emitor (VCE) maksimal 600 Volt, tegangan Gate-Emitter (VGE) maksimal ± 20 VDC, dan arus kolektor maksimal 60 Ampere.


C.Rangkaian LCD Penampil
Untuk blok ini tak ada komponen tambahan karena mikrokontroler dapat memberi data langsung ke LCD, pada LCD Hitachi - M1632 sudah terdapat driver untuk mengubah data ASCII output mikrokontroler menjadi tampilan karakter. Pemasangan potensio sebesar 5 KΩ untuk mengatur kontras karakter yang tampil. Skematik dari blok ini:


Gambar 4. Rangkaian LCD penampil

D.Perancangan Rangkaian Keypad
Keypad disini menggunakan sistem matrik dimana kolom dan baris yang sama diserikan satu sama lainnya. Perancangannya menggunakan saklar Push Button di setiap tombolnya, Push Button disini mempunyai tiga masukan yakni untuk kolom, baris, dan kommon (pada perancangan disini kommon dihubungkan ke ground). Dengan disetnya kommon dengan ground, apabila menekan tombol otomatis ketiga masukan terhubung, dengan kata lain kolom dan baris berlogika ‘0’ perubahan logika inilah yang diproses oleh mikrokontroler. Skematik dari keypad ini:


Gambar 5. Skematik rangkaian keypad

E.Sistem Minimal ATmega8535
Pengendali yang dirancang adalah menggunakan mikrokontroler dan bekerja dalam ragam single chip operation (mode operasi keping tunggal) yang tidak memerlukan memori luar karena ROM untuk menyimpan sandi sumber masih mampu untuk menampung program PWM yang akan dibuat serta penggunaan RAM yang masih bias ditampung oleh RAM dalam dan tidak memerlukan komponen tambahan seperti PPI, karena penggunaan port mikrokontroler hanya 4 port , yaitu untuk keluaran sinyal penggerak, masukan keypad, keluaran penampil, pin RS dan pin enable dari LCD penampil.
Kristal yang digunakan untuk pengoperasikan mikrokontroler adalah 8 MHz. Port yang digunakan pada sistem, yaitu Port C (PC0..PC3) digunakan untuk keluaran sinyal penggerak PWM, Port D (PD0..PD6) digunakan untuk mengambil masukan dari keypad, dan Port B (PB0..PB7) digunakan untuk menampilkan data frekuensi inputan motor dalam satuan Herzt dari hasil masukan keypad. Dan Port A (PA0..PA1) digunakan untuk pin RS dan Enable dari LCD.

Gambar 6. Rangkaian Sistem Minimal Atmega8535

F.Untai Penggerak
Untuk menggerakkan IGBT, sinyal PWM keluaran mikrokontroler harus dikuatkan terlebih dahulu dengan menaikkan tegangan dari 5 V menjadi 18 V. penggunaan komponen dioda D1 dan D4, berfungsi untuk menghindari derau yang kuat sehingga pada saat pulsa masukan tinggi penggandeng optic padam (turned off) berimpedansi rendah. Resistor R1 dan R7 dipasang sebagai pull-up masukan, sedangkan resistor R4 dan R10 sebagai resistor pull-up keluaran penggandeng optik.
Resistor R3 dan R9 berfungsi untuk mengamankan catu daya 18 volt dari arus maksimum pada kondisi peralihan (transient). Kapasitor kecil C2 dan C4 sebagai tapis derau berfrekuensi tinggi dari catu daya. Penggerak gerbang IGBT yang digunakan adalah IC MC33153. bekerja pada masukan aktif rendah, mempunyai keluaran totem pole yang mempu memberikan arus sebesar 1A. Diantara keluaran penggerak dan gerbang IGBT dipasang sebuah dioda dan dua buah resistor. Penambahan komponen ini menjadikan pemadapan (turn on) IGBT lebih lambat daripada pemadamannya. Selain itu sesuai dengan karakteristik dioda pintas (by pass), ini dapat menghilangkan derau dibandingkan jika hanya digunakan sebuah resistor.


Gambar 7. Rangkaian Penggerak IGBT

G.Perangkat Lunak Pembangkit PWM
Untuk mendapatkan data pewaktuan masingmasing sinyal penggerak PWM, maka terlebih dahulu dibuat simulasi pembangkitan sinyal PWM dengan menggunakan MATLAB. Dengan menggunakan fasilitas simulink di MATLAB maka didapatkan simulasi seperti pada gambar 8 sebagai berikut:

Gambar 8. Simulink Matlab untuk simulasi PWM

Pada tugas akhir ini akan dibuat inverter PWM sinusoida 15 pulsa setiap setengah periode. Untuk mendapatkan sinyal penggerak PWM 15 pulsa, maka dibutuhkan 16 buah sinyal segitiga setiap 1 gelombang sinusoida. Karena di pustaka simulink MATLAB tidak ada pembangkit gelombang segitiga, maka cara lainnya yaitu dengan mengintegralkan gelombang kotak. Amplitudo gelombang segitiga dibuat 5 V.

Blok pembanding1 dan pembanding2 akan membandingkan antara gelombang segitiga dengan gelombang sinusoida. Cara kerjanya yaitu jika nilai gelombang segitiga lebih kecil dari gelombang sinusoida pada saat t yang sama, maka hasilnya 1. Apabila sebaliknya, maka hasilnya 0. Demikian pula untuk blok pembanding 2 dan pembanding3 juga akan membandingkan antara gelombang segitiga dengan gelombang sinusoida.
Data diambil pada blok simout1 dan simout2, data-data yang diambil berupa deretap biner 0 dan 1 simulasi sinyal kelauaran yang ingin dihasilkan, dari data-data tersebut kemudian ditransfer dalam format heksadesimal, kemudian disimpan dalam ROM mikrokontroler. Keluaran sinyal penggerak yang diharapkan dapat dilihat pada gambar 9.

Gambar  9. Sinyal PWM yang diharapkan dari terminal motor

Perancangan perangkat lunak menggunakan bahasa assembler. Program dibuat untuk menghasilkan secara langsung keempat sinyal penggerak PWM dengan frekuensi dan indeks modulasi tertentu sesuai dengan masukan kecepatan RPM motor. Metode yang digunakan yaitu look up table berdasarkan data yang telah didapat dari hasil simulasi MATLAB. Berikut ini adalah diagram alir perangkat lunaknya:

Gambar 10. Diagram Alir Program Utama

H.Hasil Pengamatan

Isyarat yang diamati yaitu sinyal penggerak keluaran dari Port C0 dan Port C1 yang merupakan sinyal penggerak untuk pasangan penggerak TA+ dan TA-. Serta mengamati keluaran Port C2 dan Port C3 merupakan pasangan penggerak TB+ dan TB-. Untuk  memastikan bahwa sinyal penggerak yang dihasilkan sesuai dengan teori bahwa sinyal penggerak TA+,TA- dan TB+, TB-  adalah saling berkebalikan.


Gambar 11. Sinyal penggerak TA+,TA- dan TB+,TB- dari Atmega8535

Sinyal dari mikrokontroler kemudian masuk pada rangkaian penggerak untuk dikuatkan tegangannya, sehingga dirasa cukup untuk menggerak IGBT.

Gambar 12. Keluaran sinyal penggerak

Dan sinyal keluran inverter diperlihatkan pda gambar 13. sinyal ini dihasilkan dengan menggunakan frekuensi masukan 50 Hz, dengan mengamati tampilan osiloskop dibawah ini, frekuensi masukan sama dengan frekuensi keluaran yang diharapkan.

Gambar 13. Sinyal keluaran inverter pada frekuensi masukan 50 Hz

Pengujian juga dilakukan dengan mengamati kemampuan putar motor terhadap perubahan beban. Pengujian dilakukan dengan menggunakan metoda katrol yang diperlihatkan pada gambar 14.

Gambar 14. Pengujian Torsi Motor

Pertama kali dua buah timbangan harus dikalibrasi untuk memastikan pembacaan skala pada berat tertentu sudah benar. Saat dibebani dengan berat tertentu dalam kondisi seimbang jumlah berat diperoleh dari penjumlah berat timbangan 1 dan timbangan 2. Cara pengukuran torsi didapatkan dari selisih pembacaan timbangan 1 dan timbangan 2 dan hasilnya dikalikan dengan besarnya jari-jari rotor. Penelitian yang sudah dilakukan dengan cara mengubah besarnya berat beban terhadap frekuensi tertentu menggunakan indeks modulasi 1 dan pengaruhnya terhadap perubahan torsi motor.

VI.Kesimpulan

Dari hasil simulasi, pengamatan dan pengujian pada rancangan yang dibuat, dapat diambil kesimpulan sebagai berikut :
1.Sinyal PWM satu fase yang dirancang merupakan jenis PWM  sinusoida yang dibangkitkan  menggunakan sebuah sinyal sinus dan dua buah sinyal segitiga.

2.Frekuensi sinyal PWM yang dirancang mempunyai rentang frekuensi yang lebar dari 20 sampai 60 hertz dengan kenaikan setiap 1 hertz.

3.Frekuensi sinyal PWM yang dihasilkan sama dengan frekuensi masukan yang diharapkan, dengan mengamati lebarnya pulsa dalam satu perioda yang ditampilkan dengan osiloskop.

4.Rangkaian penggerak harus memiliki catu daya yang terisolasi satu sama lainnya agar benar-benar mampu memberikan tegangan picu (Vgs) yang cukup untuk membuat inverter on.

5.Pemakaian catu daya yang sendiri-sendiri dari masing-masing rangkaian penggerak berfungsi untuk membedakan referensi ground, sehingga pada saat penggerak TA+ ON atau TB- dan TB+ ON, maka tidak terjadi short circuit.

6.Untuk mengendalikan kecepatan putaran motor sinkron, kenaikan tegangan terhadap frekuensi belum dapat dilakukan secara proporsional karena kenaikan indeks modulasi masih terlalu besar.

7.Arah mulai motor untuk berputar belum konstan. Pada posisi tertentu, arah putaran motor dapat konstan.
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6/28/2011

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8-bit Digital to Analog converter(DAC)

Overview
This article aims to introduce to beginners and intermediate readers a simple solution to build a
digital to analog converter, based on the famous r/2r resistors network. This tutorial also
discuss a problem encourted by many amateurs while trying to build their own DAC, and propses a
very simple solution to that problem.
         
We are going to build an 8-bit digital to analog conveter with parallel input. If you don't know
what this means, well its simply a circuit that will take as input a digital number from 0
(00000000) to 255 (11111111), and output the relative value on a scale from 0 to 5v. if you know
nothing about binary numbers, bits, and op-amps, i suggest you learn some basic electronics
first.
The math for this process is very simple, an 8 bit converter will divide the 5 volts into 255
steps, each step having a value of:
5/255 = 0.019 V
Then the output voltage for the converter should be equal to the binary input multiplied by the
step value, e.g. for an input of 129 (1000 0001 in binary) the output voltage should be:
129 X 0.019 = 2.451V
Here is a simplified functional diagram of an 8-bit DAC.

               

The R/2R resistor network.
The digital data entring thought the 8 lines (D0 to D7) are going to be converted to an
equivalent analog voltage (V out) by the mean of the R/2R resistor network. Actually most of the
comercial Digital to Analog converter ICs are based on this same principle. The R/2R network is
build by a set of resistors of 2 values, with one of them double the other (example 10K
Follow the colors on the schematic and on the description text respectively, it can help!
and 20K), in on of my circuits I used 1M ohm and 470K ohm resistors, wich is quite near to the
R/2R ratio, and this small difference didn't cause any detectable errors in most applications.
However, if you want to build a very precise DAC, be precise when chosing the values of the
resistors that will exactly match the R/2R ratio.
    
One last note here, you can build a DAC with any number of bits you want, simple by enlarging the
resistor network, by adding more R/2R branches (like the one shaded in green), BUT you must keep
the 2R resistance connected to groud (shaded in light red)
Going through the mathematical proof for the operation of this converter can be a pain for some
of us, and I am only intending to keep things simple.

Now, in order to use this Resistor Network (also called R/2R Ladder) for real applications, you
will have to build a very simple voltage buffer circuit, which will be explained in the next
section.
 The applied circuit



Follow the colors on the schematic and on the description text respectively, it can help!
All the components are labeled on the circuit, so i'll start directly to explain how it works. to
simplify this task, i'll split the circuit into 2 main stages: the Digital to analog converter
and the Voltage buffer stage.
 Stage 1: the Digital to analog converter (The R/2R network)
This part have been explained in detail in the previous section, its purpose is to create the
voltage V1 which is equivalent to the weight of the binary number on the lines (D0 to D7). Now
that this is a resistor network, if we apply any load on the output of the first stage, this load
will be considered as an additional resistor in the network, and thus will disturb the network
which will no longer provide the correct & desired output voltage. Therefore, to overcome this
problem, we need a voltage buffer, here is where the next stage comes...
 Stage 2: the voltage buffer
This stage will isolate the point V1 from the final output V2, while allways keeping the voltage
V2 at the exact same value of V1. This is what we call a voltage buffer. for the voltage buffer
we use an opamp with the ouput connected to the inverting input (this special configuration of
the Op Amp is also called Voltage Follower). The most imortant things to note are:

1.  No current (almost 0A) will flow from the point V1 into the opamp, so we wont be disturbing
    the resistor network configuration
2.  V2 will allways equal V1 (theoretically, see the rest of this document)
3.  The current going out from the point V2 to any other stage is sourced from from the power
     supply of the OpAmp.
 The most encourted problem & some solutions
A quick look on those 2 graphs can be sufficient to understand the problem: the output of the
op-amp is not linear on the full 0-to-Vcc scale. actually an OpAmp, depending on its type, will
deliver a maximum voltage of (Vcc - 0.5V), where Vcc is the supply voltage of the OpAmp. So, in
our application, the OpAmp will only deliver 4.5V even if theoretically it should deliver 5V.

Some of you may think this caused by the resistor network, but it's not! this is a limitation in
the op-amp itself.
Lets get a litle deeper into the problem, the actual output curve in red should be linear, but
actually it begins loosing its linearity beginning from 3.9 volt. (Again this depends on the type
of OpAmp, those results a based on my own tests on a LM350 OpAmp) The red 'Error zone' is where
the output of the DAC no longer math the relative binary input.

This is the error we will be trying to overcome in the next part, through 2 very simple
solutions.             
 Solution 1 :


The first solutions - shown in the red shading - is to increase the supply votage of the Op-Amp,
as shown in the schematic. this will totally solve the problem, and, wether you are supplying 6.5
volts or more, you will get neat linear ouput from 0V to 5V.
 Solution 2 :


The second solutions - shown in the red shading - is to reduce the range of the input to [0 to
127] from the original range of [o to 255]. This will result on a voltage swing of 0 to 2.5 volt
at the output, which will be in the linear operating area of the Op-Amp (this done by attaching
the MSB line to ground, this way you only control the 7 other lines, and a 7 bit value can swing
from 0 to 127).
Finally with what you should have learnt in this introduction, you should be able to build
reliable DACs to suit any application like generating all kind of wave-forms.
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6/25/2011

Making Windows XP Start Faster

Booting up your computer can be a slow process, and quite inconvenient when you are in a hurry to start a class or grab a document on your way out the door. There are a few can techniques you can perform however, that help Windows XP boot a little faster.

Stopping Unneeded Startup Services
Along with the core operating system and programs that Windows XP runs when it starts, there is also a host of services involved. Many of these services are necessary for Windows XP to operate correctly. However, many of them are for features in Windows XP that you may not use at all. You can peruse the services and disable any service that you do not want to run. The fewer services that run, the more quickly Windows XP will boot.

Caution:
Exercise caution when stopping services. If you do not know what a service does or are unsure of the ramifications of stopping the service, leave it alone. Some services are critical to Windows XP's operations, so make sure you understand what the service is before you disable it.


To reduce the number of services that start on bootup, you can access two different areas of Windows XP. The first is the System Configuration Utility. The Services tab shows you the services that start when the computer boots (see Figure 4-1).

You can stop a service from starting by simply clearing the check box next to the service and clicking OK. However, before you do so, there is another way to disable services that you may prefer because the interface gives you more information about the service in question.

Open Control Panel/Administrative ToolsServices or else select Start/Run, type services.msc, and click OK. Either way, you see the Services console (see Figure 4-2).

I prefer to use the Services console instead of the System Configuration Utility because it describes what the service does. Additionally, you can double-click a service and examine its properties.

Notice the Startup Type column in Figure 4-2. This information lists whether the service is automatic or manual. Manual services are only started in Windows XP when you start a process that requires the service. Some other process may require the service that has a "dependency" relationship with it; in this case, the dependency service will start, as well. Because these services do not start automatically when you boot Windows XP, you do not need to do anything with manual services.

However, all services listed as automatic start when Windows XP boots. These are the services that increase boot time. As I have mentioned, many of them are necessary and important, so you should not stop automatic services from booting unless you are sure of the ramifications. You can get this information by looking at the Description column. Here's a quick look at common services you may want to live without:

·         Automatic Updates: This service enables Windows XP to check the Web automatically for updates. If you don't want to use Automatic Updates, you can disable the service. You can always check for updates manually at the Windows Update Web site.

·         Computer Browser: If your computer is not on a network, you don't need this service. If you are on a network, leave it alone.

·         DHCP Client: If you are not on a network, you do not need this service. If you are on a small workgroup, you can still increase boot time by configuring manual IP addresses (which I explore later in this chapter).

·         DNS Client: If you are not on a network, you do not need this service. If you are, leave it alone.

·         Error Reporting and Event Log: You don't have to use these services but they can be very helpful, so I would leave them configured as automatic.

·         Fax: If you don't use your computer for fax services, you can disable this one.

·         Help and Support: If you never use the Windows XP Help and Support Center (found on the Start menu), you can disable this service.

·         IMAPI CD-Burning COM: This service enables you to burn CDs on your computer. If you never burn CDs, you can disable the service.

·         Indexing Service: Your computer keeps an index of files but if you rarely search for files, the service is just a resource hog. You can stop it and turn the service to manual.

·         Windows Firewall/Internet Connection Sharing: If you do not use these features, you can disable them.

·         Infrared Monitor: If you do not use infrared devices, you can disable this service.

·         Messenger: This service sends alert messages on a local area network (it is not the same as Windows Messenger). If you are not on a network, you can disable this service.

·         Print Spooler: If you do not do any printing from the computer, you can disable this service. If you print, make sure you leave it as automatic.

·         Remote Registry: This service allows remote users to modify the Registry on your computer. If you are not on a network, you can disable this service.

·         System Restore Service: This service allows you to use System Restore. If you have turned off System Restore anyway, you do not need to turn off the service. If you do, you turn off System Restore.

·         Themes: If you do not use themes, you can disable this service.

·         Windows Image Acquisition: If you do not use scanners or digital cameras, you can disable this service.

·         Wireless Zero Configuration: If do not use wireless networking devices, you can disable this service.

You may have a number of other automatic services, depending on software and other configurations on your computer. So it's a good idea to look through the services and learn more about them. If you double-click a service, a Properties dialog box appears (see Figure 4-3).


Notice that on the General tab, you see a Startup Type drop-down menu. If you want to change an automatic service to manual, select Manual here and click OK. As a general rule, don't disable a service unless you are sure you will never use it. However, manual configuration allows the service to be started when you find it necessary, thus speeding up your boot time.

However, before you change a service to manual, look at the Dependencies tab (see Figure 4-4). This tab shows you which other services depend upon the service you are considering changing.



Keep in mind that services are necessary for the vast functionality you get with Windows XP. Change only those services that you understand and do not use. How you use your Windows XP computer should be the best guide in terms of optional startup services.

Tip:
The Indexing service and the System Restore service take up a lot of disk space and system resources across the board. You can live without the Indexing service but I suggest that you keep using System Restore. It works great when you are in a bind and this is one case where the loss of speed may not be worth the ramifications of not using System Restore.

Disabling Recent Documents History

Windows XP includes a feature that keeps track of all recent documents you have opened or used. The idea is that you can select Start/Recent Documents History and quickly reopen any document you have recently used. I use many documents each day and never use the feature myself. In my opinion, I can keep up with what I want to use without Windows XP doing it for me.

The bad thing about Recent Documents History is that Windows XP has to calculate what should be put there each time you boot Windows, which can slow things down. So, if you never use the Recent Documents History, it's a good idea to disable it. Here's how:

1. Open the Registry Editor (select Start/Run, type regedit, and click OK).

2. Navigate to HKEY_CURRENT_USER\Software\Microsoft\Windows\ CurrentVersion\Policies\Explorer.

3. Create a NoRecentDocsHistory D_WORD key. Double-click the value to open it once it is created.

4. Set the Data Value to 1 to enable the restriction.

5. Click OK and close the Registry Editor. You'll need to restart the computer for the change to take effect.

Disabling the Boot Logo

You can remove the boot logo that appears when you start Windows XP. This little tweak probably shaves only a few seconds off your boot time but seconds count if you are serious about trying to get Windows XP up and running as quickly as possible. The only negative is that if you remove the boot logo, you will also not see any boot messages, such as check disk. (But if you are not having problems with your computer, this isn't such a big deal.)

To remove the boot logo, follow these steps:

1. Select Start/Run, type msconfig, and click OK.

2. In the System Configuration Utility, click the BOOT.INI tab.

3. On the BOOT.INI tab, click the NOGUIBOOT check box option (see Figure 4-6). Click OK.


Stopping Remote Assistance and Remote Desktop Sharing

In Windows XP Professional, you have two remote networking features called Remote Assistance and Remote Desktop Sharing. These remote networking features are very helpful in a variety of situations but if you don't use them, it is good idea to disable them to save boot time. You can always enable them later if you want to use them.

Note: If you are interested in using Remote Desktop or Remote Assistance, see my book Windows XP for Power Users: Power Pack published by John Wiley & Sons.

1. Open the Start menu, right-click My Computer, and choose Properties.

2. Click the Remote Tab.

3. Clear both check boxes to disable Remote Assistance and Remote Desktop (see Figure 4-7).



Updating Device Drivers (Home Computer)

One thing that can slow down your boot time is old device drivers. If you are using a newer computer that came preconfigured with Windows XP, you can skip this section. But if you are using older hardware that you have manually installed with the manufacturer's device drivers, it is a good idea to locate the manufacturer's Web site and see if there are any updated drivers for the hardware.

Windows XP tries very hard to be backwards-compatible with older hardware so older drivers will often work. However, older drivers tend to slow things down across the board, including the time required to boot the system. The only way you can update older drivers is to download newer drivers that the manufacturer of the device may make available on the Web. You'll have to do a bit of detective work and see if you can locate any newer drivers that can be installed. It's worth the time, though, because drivers written for Windows XP simply perform better than drivers for older versions of Windows.

Stopping Windows Messenger in Outlook Express 6

If you are using Outlook Express 6, Windows Messenger is configured to start when Windows XP starts and run in the background. That's fine if you use it, but if you don't you waste boot time and background resources because Windows Messenger is always around. You can stop this behavior, however, and save your self a little startup time by following these steps:

1. Open Outlook Express 6.

2. Select Tools/Windows Messenger/Options.

3. Click the Preferences tab.

4. On the Preferences tab, clear the "Allow this program to run in the background" check box (see Figure 4-8) and click OK.



Speeding Up Logons to Windows Domains

Although not technically a part of the boot process, one thing that can slow down your startup time is logging onto a Windows domain. If you do not connect to a Windows domain, you can skip this section. If you do and you notice that logging on seems to take forever, there is a simple explanation. Windows XP attempts to load up networking components asynchronously during startup. Although you can log on using cached credentials instead of waiting for a domain controller to log you on, this feature may greatly slow down your logon process to the network. You'll see your desktop more quickly but you'll have to wait longer to use the network. If you change this setting, your boot time will take longer. But at least once you log on you won't have to wait for the networking services to load. You can stop this behavior by changing a Group Policy setting on your computer.

Follow these steps:

1. Log on as the local computer administrator and select Start/Run. Type gpedit.msc and click OK.

2. In the Group Policy editor, navigate to Computer Configuration/Administrative Templates/System/Logon (see Figure 4-9).

3. Double-click "Always wait for the network at computer startup and logon."

4. Change the setting to Enabled (see Figure 4-10). Click OK and close the Group Policy console.


Speeding Up the Dual-Boot Timeout

If you dual-boot your computer with Windows XP and another operating system, you see an operating system selection menu on startup. If you typically boot into Windows XP and not the other operating system, you can speed up the dual-boot timeout value so that you do not wait so long for the boot process to select your default operating system and continue with the boot process. The default timeout value is 30 seconds but you can change this setting to 10. This gives you enough time to select the alternate operating system if you want but also speeds up the boot process. You can skip this section if you do not use a dual-boot configuration.

Follow these steps:

1. Locate the boot.ini file on your computer. It is a hidden file by default; mine is located in C:\boot.ini.

2. Open the file with Notepad (which is what opens it by default).

3. Change the Timeout value to 10 (see Figure 4-11).

4. Select File/Save and close Notepad. 



Speeding Up Your PPPoE Connection

If you use a Point-to-Point Protocol connection over Ethernet (PPPoE), you may notice a delay in using the PPPoE connection after startup. By default, there is a 120 second delay but you can stop this behavior by manually configuring an IP address for the network adapter card. If you do not use a PPPoE connection, you can skip this section.

1. Select Start/Connect to/Show All Connections.

2. Open the TCP/IP properties for your LAN network interface card.

3. Manually set the IP address on the TCP/IP properties to an appropriate IP address and subnet mask for your network.

Editing the PC Setup Program

Each PC has a setup program that tells the computer how to start the operating system. We often think that speeding up the boot time means speeding up Windows XP. While that's true, the PC setup program also governs some of the items that occur when the computer starts—which you can speed up as well.

Typically, you can enter the PC setup program by starting the computer and holding down the Delete key. A different key may be used for your computer's setup program, so check your computer's documentation for additional details.

Once you are in the setup program, you may have to look around a bit. Each manufacturer uses different categories and names, but essentially you can wade through the menu options and find these three common features to change to decrease your startup time:

    Quick Power on Self-Test: Set this option to Fast or Enabled, depending on your setup program. This change will result in skipped memory and hardware startup tests. Be aware that this setting might cause you to lose notice of a problem with RAM or the motherboard but, in most cases, you don't need this test anyway if your PC is operating without problems.
    Floppy Search/Test: If your floppy disk drive is working fine, there is no reason to test it every time you start your computer. Change this setting to Disable.

    IDE Drives: The setup program seeks to test and identify each IDE device as it boots. This is necessary but if you have IDE channels that are not in use, set this to None. If you do not understand this option, just leave it configured as it is.

Note:
Cleaning up the Registry and defragmenting the hard drive can also increase your boot time.

Disabling Unused Devices

If you have devices attached to your computer or installed that you do not use, you can reduce the startup time by disabling those devices. The rule to follow is to keep enabled any device that you use or might use, but if you have devices that you do not use on a regular basis, you can disable those devices without uninstalling. When you start the computer, those devices' drivers won't have to load, which will help decrease boot time.

To disable a device, follow these steps:

1. Open the Start menu, right-click My Computer, and select Properties.

2. Click the Hardware tab and click the Device Manager button.

3. Expand the category that contains the device that you want to disable.

4. Right-click the device and click Disable (see Figure 4-12). The device is now disabled and remains disabled until you re-enable it in the same manner.



About BOOTVis

If you poke around on the Internet a bit and search for ways to reduce your computer's boot time, you may find information about a BOOTVis utility. BOOTVis is a Microsoft- developed utility for system architects who design systems for faster boot times. According to Microsoft, many published reports on the Internet state that you can download the BOOTVis utility and run it on your PC to improve your boot time. However, Microsoft also states that the utility was not developed for this purpose and it will not increase the boot time in Windows XP because Windows XP already performs the routines that BOOTVis performs. In short, it is an Internet myth that BOOTVis can help you. Do not waste your time running this utility. Visit www.microsoft.com/whdc/system/sysperf/fastboot/bootvis.mspx to learn more about this.


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