September 18 2009 - Activity

Saturday, September 19, 2009

Test Your PSU's Voltage Rails With A Multimeter

The best way to get the most accurate readings from your PSU is to use a multimeter. Hardware monitors, and BIOS will not give you TRUE real voltages on those 3 main voltage lines. Many people still rely on means of software, such as MBM, Speedfan, and the BIOS, but these are all very unreliable.

More about software/bios readings on the rails:

In order for the software to read your PSU's rails, or lines of voltage required to run your computer properly, a chip on your motherboard needs to read these voltages. There is usually resistance between the PSU and the monitoring chip on the motherboard. According to a motherboard monitoring software, an 12-volt Rail can be way under spec. You want your voltage to be within 4%. So you want your 12-volt rail to be within 11.52 to 12.48 during load. This means when you are running your CPU at 100% you do not want to drop below 11.52 or you may experience stability problems including but not limited to system restarts and Windows crashes. For the 5-volt rail, you want it to be within 4.8 to 5.2 to be within the 4% range. As for the 3.3 volt rail, you want it to be within 3.17 to 3.43.

What are RAILs?

Rails are the above mentioned voltage lines coming from your PSU to your motherboard and devices in your motherboard. The 3.3-volt and 5-volt generally power the devices like the motherboard, PCI slots, AGP slot, etc. The 12-volt is usually used for things with motors like the hard drives, CD-ROM, fans, etc.

What's a multimeter / voltmeter?

A multimeter is an electronic measuring instrument that combines several functions in one unit. The most basic instruments include an ammeter, voltmeter, and ohmmeter.

A multimeter can be a handheld device useful for basic fault finding and field service work or a bench instrument which can measure to seven or eight and a half digits of accuracy. Such an instrument will commonly be found in a calibration lab and can be used to characterize resistance and voltage standards or adjust and verify the performance of multi-function calibrators.

The 1st pic is a Digital Multimeter, and the 2nd is an Analog Multimeter:



Preparations:

CAUTION: This test involves using probes with the computer ON. Please only do this if you feel competent enough to be dealing with electricity. If you short rails, you could risk damaging the PSU and possibly your components. I cannot be held responsible if something goes wrong, this is merely a guide. If you feel any concern, please post BEFORE doing this, and we will be glad to help.

If you are afraid of doing such a thing and you are not sure what any of this guide means, I encourage you to NOT do this. Electricity is dangerous and can kill you in a heartbeat. Remember this is only a thread, what informs you, on how to do this. If you aren't sure of what you doing, DON'T DO IT.

Firstly, you will have to set up the multimeter to read the voltages you will be measuring. You should be able to move a dial on the multimeter. You want to move this to the number 20 (like this), in the section which relates to DC voltage. This is usually represented by THIS symbol.
Put The Black probe into the 'COM' plug on the multimeter. The Red probe should be placed in voltage detection plug.
DO NOT insert the probe into the 'current detection' plug, which on cheaper MM's usually has a '10A max or 10ADC' Label.

More preparations:

The first thing you want to do is download Prime95. Download it here. Prime95 is used to put your system at full load. You want your system at full load when checking your voltages to ensure your PSU is up to spec. The whole point is to make sure your PSU can handle what your system asks of it. This can only be done by stressing your system during the voltage test.

Now you want to shut down your system and then open the side so you have access to your AUS and a Molex plug. How to test with the Molex plug is discussed later in the guide. Lay your computer on it's side during this test or this will be more difficult than necessary.
Locate a free 4 pin Molex Connector, although you can test the back of molex connectors, if you have non spare, it just might be a bit more akward.
Locate the AUX connector:


And pull these into an area free from any clutter, so they are accessible for the probes on your multimeter. This may be a good time to do some cable rearrangement.

Measuring the VOLTAGEs:

Time to start. You want to observe these 3 voltages in all states. So you will have to set up the probes BEFORE you turn the PC on, because you want to observe the voltages for.

* POST
* Boot
* Windows Start up
* System at Idle
* System at Load
* Shutting Down


That is the problem with most PSU measuring guides, they test the PSU externally, with only the load of maybe a few fans, which does NOT give any real kind of indication on how the PSU copes powering a computer. So, set up each of these measuring, and observe/record the voltages at each stage as listed above. Ideally, they should not go above or below the rated voltage, though no component is perfect, which is why there is an ATX specification, which sets parameters for each voltage.

It is my opinion though, that any PSU which falls close to the min ATX spec, needs replacing.
Another Purpose of these rail tests are to find out how much your rails fluctuate, and if they do a lot, even if they stay within ATX spec, id suggest replacement. Clean, Stable voltage is just as Important as enough Voltage.



STEP 1: Measuring The 12V Rail

For this you just need the 4-pin Molex. Insert the red probe into the yellow 12v connector, and the black probe into any black Ground connector on the Molex:



STEP 2: Measuring The 5V Rail

For this you just need again the 4-pin Molex. Insert the red probe into the red 5v connector, and the black probe into any black Ground connector on the molex:



STEP 3: Measuring The 3.3V Rail

For this you will need the a.> AUX Connector Only, OR b.> a combination of the AUX and 4-pin Molex.
Insert the red probe into either one of the two orange 3.3v connectors on the AUX connector
Insert the black probe into any of the black ground connectors on the AUX connector, or the 4-pin Molex connector.

Note: Some people may struggle to insert the probe into the aux connector like is pictured, but you can also test the rail via the back of the connector.

method1: Using Just AUX Connector:

method2: Using AUX and 4-pin Molex:



Another way of testing this is in the DriverHeaven's Guide, their method is involving the 20pin Motherboard plug and a Molex Plug.

method3: Using 20pin plug:


More info about using the 20pin method, relating that you can measure the 3.3v,5v,12v from that single 20pin plug:

Orange, Red and then Yellow. 3.3, 5 and 12 volts respectively.

Make sure you have the multimeter on the correct setting if it is not auto-switching. I put mine on DC or Direct Current and on the "20" volt setting where you will get the most accurate results in this range.
Between each Rail testing you should have the appropriate voltage range on the multimeter. For example if you are testing the 12-volt rail (Yellow wire) then your voltage should be in the 12 volt range. Double check and make sure you have your multimeter.

September 17 2009 - Activity

Thursday, September 17, 2009

Manually Test a Power Supply With a Multimeter

Read Important PC Repair Safety Tips. Manually testing a power supply involves working closely with high voltage electricity. Important: Do not skip this step! Safety should be your primary concern during a power supply test and there are several points you should be aware of before starting this process.

Open your case. In short, this involves turning off the computer, removing the power cable and unplugging anything else connecting to the outside of your computer. To make testing your power supply easier, you should also move your disconnected and open case somewhere easy to work like on a table or other flat, non-static surface.

Unplug the power connectors from each and every internal device. Tip: An easy way to confirm that each power connector is unplugged is to work from the bundle of power cables coming from the power supply inside the PC. Each group of wires should terminate to one or more power connectors. Note: There is no need to remove the actual power supply unit from the computer nor is there any reason to disconnect any data cables or other cables not originating from the power supply.

Group all of the power cables and connectors together for easy testing. As you're organizing the power cables, I highly recommend rerouting them and pulling them as far away from the computer case as possible. This will make it as easy as possible to test the power supply connections.

Short out pins 15 and 16 on the 24-pin motherboard power connector with a small piece of wire. You'll probably need to take a look at the ATX 24 pin 12V Power Supply Pinout table to determine the locations of these two pins.

Confirm that the power supply voltage switch located on the power supply is properly set for your country. Note: In the US, the voltage should be set to 110V/115V. Check the Foreign Electricity Guide for voltage settings in other countries.

Plug the PSU into a live outlet and flip the switch on the back of the power supply. Assuming that the power supply is at least minimally functional and that you've properly shorted the pins in Step 5, you should hear the fan begin to run. Important: Just because the fan is running does not mean that your power supply is supplying power to your devices properly. You'll need to continue testing to confirm that. Note: Some power supplies do not have a switch on the back of the unit. If the PSU you're testing does not, the fan should begin to run immediately after plugging the unit into the wall.

Turn on your multimeter and turn the dial to the VDC (Volts DC) setting. Note: If the multimeter you're using does not have an auto-ranging feature, set the range to 10.00V.

First we'll test the 24 pin motherboard power connector: Connect the negative probe on the multimeter (black) to any ground wired pin and connect the positive probe (red) to the first power line you want to test. The 24 pin main power connector has +3.3 VDC, +5 VDC, -5 VDC (optional), +12 VDC, and -12 VDC lines across multiple pins. You'll need to reference the ATX 24 pin 12V Power Supply Pinout for the locations of these pins. I recommend testing every pin on the 24 pin connector that carries a voltage. This will confirm that each line is supplying the proper voltage and that each pin is properly terminated.

Document the number that the multimeter shows for each voltage tested and confirm that the reported voltage is within approved tolerance. You can reference Power Supply Voltage Tolerances for a list of proper ranges for each voltage. Are any voltages outside the approved tolerance? If yes, replace the power supply. If all voltages are within tolerance, your power supply is not defective. Important: If your power supply passes your tests, I highly recommend you continue testing to confirm that it can operate properly under a load. If you're not interested in testing your PSU further, skip to Step 15.

Turn off the switch on the back of the power supply and unplug it from the wall.

Reconnect all of your internal devices to power. Also, don't forget to remove the short you created in Step 5 before plugging back in the 24 pin motherboard power connector. Note: The biggest mistake made at this point is forgetting to plug everything back in. Aside from the main power connector to the motherboard, don't forget to provide power to your hard drive(s), optical drive(s), and floppy drive. Some motherboards require an additional 4, 6, or 8 pin power connector and some video cards need dedicated power too.

Plug in your power supply, flip the switch on the back if you have one, and then turn on your computer as you normally do with the power switch on the front of the PC. Note: Yes, you'll be running your computer with the case cover removed which is perfectly safe as long as you're careful. Note: It's not common, but if your PC does not turn on with the cover removed, you may have to move the appropriate jumper on the motherboard to allow this. Your computer or motherboard manual should explain how to do this.

Repeat Step 9 and Step 10, testing and documenting the voltages for other power connectors like the 4 pin peripheral power connector, the 15 pin SATA power connector, and the 4 pin floppy power connector. Note: The pinouts necessary to test these power connectors with a multimeter can be found in my ATX Power Supply Pinout Tables list. Just as with the 24 pin motherboard power connector, if any voltages fall too far outside the listed voltage (see Power Supply Voltage Tolerances) you should replace the power supply.

Once your testing is complete, turn off and unplug the PC and then put the cover back on the case. Assuming your power supply tested good or you've replaced your power supply with a new one, you can now turn your computer back on and/or continue troubleshooting the problem you are having.


Pin Name Color Description
1 +3.3V Orange +3.3 VDC
2 +3.3V Orange +3.3 VDC
3 COM Black Ground
4 +5V Red +5 VDC
5 COM Black Ground
6 +5V Red +5 VDC
7 COM Black Ground
8 PWR_ON Gray Power Good
9 +5VSB Purple +5 VDC Standby
10 +12V1 Yellow +12 VDC
11 +12V1 Yellow +12 VDC
12 +3.3V Orange +3.3 VDC
13 +3.3V Orange +3.3 VDC
14 -12V Blue -12 VDC
15 COM Black Ground
16 PS_ON# Green Power Supply On
17 COM Black Ground
18 COM Black Ground
19 COM Black Ground
20 NC White -5 VDC (Optional - Removed in ATX12V v2.01)
21 +5V Red +5 VDC
22 +5V Red +5 VDC
23 +5V Red +5 VDC
24 COM Black Ground

September 16 2009 - Activity

Wednesday, September 16, 2009

Troubleshooting An Ailing Power Supply

The Power Supply convert's your regular household current into low DC voltage used by the computer. When this component fails,there is simply no activity going on wih your computer.Remember to do the
easy troubleshooting first.Inspect the Power Supply
for any damage.Double-Check all connections.

Learning how to check your power supply and how to replace it when needed can be a life saver if you're a computer buff or in business with the trusted PC.Don't take for granted the sinple pleasure of turning on your PC and everything works just fine.

We turned on one of our computer's recently and if about one hour,it just re-booted itself.And it continued doing so about 10 times a day until we found out the power supply was the culprit.Things to look for when your power supply is going bad or just dies on you are the following....

NO POWER TO THE COMPUTER

Here you must first check the wall outlet for power by connecting another device such as a radio or lamp to be sure power is present.If the computer is connected through a surge protector,check it
as well.

If the wall out has power,check the power cable going to the PC to see if AC voltage is making its way to the system unit.Do this with the use of a multimeter.If there is power,you will have to open the computer and check for power from the power supply to the motherboard.When using a multimeter to check voltage,be sure you have a good ground for the black lead of the multimeter.

RE-BOOTING PROBLEMS

One main problem you may face with an ailing Power Supply is that it may re-boot the computer without any warning.All information is lost and it seems as though this happens at the worst possible time.Booting errors when the computer first start's up is another indicator of this component going on the blink.

POWER DISTRIBUTION PROBLEMS

When the power supply begins to fail,you may receive power at one device and not another.For example,the Hard Drive may receive power but the CDROM Drive has nothing at all.

Another headache with would cause re-booting is the intermittent power going to the drives or the motherboard itself.Follow the steps below to check your power supply should you experience some of the above problems.

CHECKING THE POWER SUPPLY

If the wall outlet,and the power cord are good,as well as the connection at the motherboard is secure.Then you may have to face the fact that the power supply itself is bad.If you have a Multimeter you can test the power supply output before purchasing a new one.Simply follow these steps.

Turn off the PC,but do not unplug it,open the system unit.Set the multimeter to read DC volts in the next range higher than 12 volts.Locate a power connector similair to the hard drive,or floppy drive connector that is unused and turn on the PC.You can also unplug a drive connector and use it as well.Turn on the PC and insert the BLACK probe into the power connector on one of the BLACK wires.Touch the RED probe to the YELLOW wire onthe power connector.

The multimeter reading should be +12 volts.Now touch the RED probe to the RED wire and the reading should be +5 volts.If no readings or different readings occured,you,ll have to replace the power supply.If the readings were correct,you should check the P8 or P9 connectors at the motherboard.These connectors may also be named P4 and P5.To check these connectors,perform the following...

Insert the BLACK probe into P8 at one of the BLACK wires.Insert the RED probe into the P8 connector at the RED wire.The readingon the multimeter should be +5 volts

Check the power going to the Motherboard connections by inserting the RED probe into P8 at the YELLOW wire and you should get +12 volts.Leave the BLACK wire touching the black wire at the P8 connector.Check the BLUE wire and the reading should be a -12 volts.

Now move the BLACK probe to the BLACK wire on the P9
connector.Test the WHITE wire by inserting the RED probe and the reading should be -5 volts.Check the RED wires on the P9 connector and you should get +5 volts on each red wire.You won,t get exactly 5
or 12 volts but the readings will be very close,such as 5.02 volts.

If the Power Supply is a couple of volts off,in either direction,such
as when the RED wire should be reading -5 volts but it reads -8
volts,or if there are no readings,replace the power supply.

DO NOT remove the power supply from the system unit case when performing these tests.DO NOT perform these tests if you do not feel comfortable.Be sure to remove any and all electrical static build-up from your clothes and body BEFORE touching any parts inside the system unit.And NEVER open the power supply case for any reason,since high voltage may be present.

Should this be called Islamic Researchology? - New Word (phraseology)

Tuesday, September 15, 2009
What is Research?
A method or a way for founding new thing example technology and literary (word founding)

What is Ology?
Ology comes from the greek logos, meaning the "study of" something. There are an incredible amount of different branches of science, thus there are a lot of ologies, and this is list is designed to define as many as possible. Note: many of these ologies start with the prefix paleo- it is greek for old or ancient.

What is Researchology?
An education method on how to do a research

What is Islamic Researchology?
An education method on how to do a research or buying a technology base on holy Quran & Al-Sunnah

Implementation
1. Idea
2. Know the boundry from Al-Quran or Al-Sunnah - (example Human Rights)
3. Pray
4. Do

Example on how Islamic research being done
- The Founding of Sound Technology or Radio wave
- Fitnah/Fitna is a word or act that can be done from sound and articles "Sound->Mouth, cassette, cd"
- Know the healthy boundary from Al-Quran, Example Fitnah can kill a someone by Al-Sunnah
- Parying
- Do - Qada & Qadar

How this can Fitnah/Fitna effect someone or a community?
A Proof method has been shown by our community by using an ocean or birds sound/cassette/cd to ease the mind and this method has shown us how can mind being influenced by the Founded Technology (Sound Technology).

Fitnah how can it be connected by the word or act "Killing someone"
1. Killing the identity or pride of the accused by using the world community
2. Changing the Reality by Killing a person using the community to turn around the accused mind. (Formula: Education (Sound and articles) -> Community -> Mind Believing -> Depression -> Reality Changes -> madness or crazy)

Why does the Islamic Researchology should be practice?
God has give us a path to healthy life using Al-Quran and al-sunnah.
Example :
Praying
If someone did not pray this will cause them a ear diseases (Cleaning ears 5 time a day will wipe the germ, before praying - pray water)

How can Islamic Researchology effect us?
Islamic Future Community means being forwarded using the Islamic healthy lifestyle by conducting the Islamic Researchology before doing some research on interested idea.

How can this word foward our future community?
Syaitan/Satan pissing his ears..............
1. a future community with an understandment that a syaitan/satan pissing on his ears (imagination)
-Causing Mental Ilness (Seeing Ghost)
2. a future community with an understandment of being lie to and disease are spreading

How can a future community forwarded?
Creation of "Word"and educate them, Example :
Believing is "Be" "Lie" "ing" is created by someone smart be course of the combination
- Be : root word, become, understand
- Lie: not true
- ing: do, act

What happen to Malaysia future community with this word differences combination between melayu and english ?
Example word creation:
Melayu means Caj and in English means Charge
Melayu means Nyah Caj and in English means Discharge
Melayu means Buka and in English means Enable
Melayu means Tutup and in English means Disable

Did you see the word "Dis" are being used by the english?
How many word load must Malaysian learn? Student are suffering so many work load tu understand the word and rembering them.

Malaysia Future Community is?
1. Heavy work load?
2. Eased work load?

Are we trying to "Merdeka" the word? and making the work load more, meaning of this Merdeka word is by using our own creation example of NOT merdeka word:
Melayu means Nyah Caj and in english means discharge, the caj or charge is a word (with same pronousation) that are not created by the Melayu Literator (Sasterawan), and this is what i call are not "merdeka" word.
("Nyah" is a merdeka word)

Solution:
Why can't Malaysia use our old traditional ways of creating new word for education and this will minimize the work load for the student (same pronousation)? example:
1. Discaj = Discharge

2. Politik = Politic


Positive:
- Work Load is easier
- Melayu language are still not wipe because of the spelling (Nationality Pride)

Negetive by some oppinions may accur:
By Following the method above there will be some difficulties that may occur in future example, "Melayu Hilang Di Dunia" (Melayu Language is wipe)

If we choose to Merdeka the word, Should the word combine with the islamic word to keep their faith in future?
- What about other student with that are not islam?
- Everything new are wierd for the first time until the community is teach each other how to use it and become fimiliar with it and no more oppinion being discuss (Forgotton)


Articles discussing the new malaysia ways educating our children
http://www.miricommunity.net/viewtopic.php?f=1&t=22586


For us to remember
Will Melayu be Wipe?
Melayu tidak akan hilang di dunia - Dato' Hang Tuah

Sincerely,
Muhd Khairi Rijal bin Farouk

September 14 2009 - Activity

Monday, September 14, 2009

Power Supplies

There are many types of power supply. Most are designed to convert high voltage AC mains electricity to a suitable low voltage supply for electronics circuits and other devices. A power supply can by broken down into a series of blocks, each of which performs a particular function.

For example a 5V regulated supply:



Each of the blocks is described in more detail below:

* Transformer - steps down high voltage AC mains to low voltage AC.
* Rectifier - converts AC to DC, but the DC output is varying.
* Smoothing - smooths the DC from varying greatly to a small ripple.
* Regulator - eliminates ripple by setting DC output to a fixed voltage.

Power supplies made from these blocks are described below with a circuit diagram and a graph of their output:

* Transformer only
* Transformer + Rectifier
* Transformer + Rectifier + Smoothing
* Transformer + Rectifier + Smoothing + Regulator

Also See: AC and DC | Diodes | Capacitors

Voltage Output For Transformer + Rectifier + Smoothing + Regulator

The regulated DC output is very smooth with no ripple. It is suitable for all electronic circuits.



Further information: Transformer | Rectifier | Smoothing | Regulator

Voltage Output For Transformer + Rectifier + Smoothing

The smooth DC output has a small ripple. It is suitable for most electronic circuits.



Further information: Transformer | Rectifier | Smoothing

Voltage Output For Transformer + Rectifier

The varying DC output is suitable for lamps, heaters and standard motors. It is not suitable for electronic circuits unless they include a smoothing capacitor.



Further information: Transformer | Rectifier

Voltage Output For Transformer only

The low voltage AC output is suitable for lamps, heaters and special AC motors. It is not suitable for electronic circuits unless they include a rectifier and a smoothing capacitor.



Further information: Transformer

Regulator

Voltage regulator ICs are available with fixed (typically 5, 12 and 15V) or variable output voltages. They are also rated by the maximum current they can pass. Negative voltage regulators are available, mainly for use in dual supplies. Most regulators include some automatic protection from excessive current ('overload protection') and overheating ('thermal protection').

Many of the fixed voltage regulator ICs have 3 leads and look like power transistors, such as the 7805 +5V 1A regulator shown on the right. They include a hole for attaching a heatsink if necessary.




Voltage Regulator

Please see the Electronics in Meccano website for more information about voltage regulator ICs. Pl - http://www.eleinmec.com

Zener diode regulator

For low current power supplies a simple voltage regulator can be made with a resistor and a zener diode connected in reverse as shown in the diagram. Zener diodes are rated by their breakdown voltage Vz and maximum power Pz (typically 400mW or 1.3W).

The resistor limits the current (like an LED resistor). The current through the resistor is constant, so when there is no output current all the current flows through the zener diode and its power rating Pz must be large enough to withstand this.

Please see the Diodes page for more information about zener diodes.

Choosing a zener diode and resistor:

1. The zener voltage Vz is the output voltage required
2. The input voltage Vs must be a few volts greater than Vz
(this is to allow for small fluctuations in Vs due to ripple)
3. The maximum current Imax is the output current required plus 10%
4. The zener power Pz is determined by the maximum current: Pz > Vz × Imax
5. The resistor resistance: R = (Vs - Vz) / Imax
6. The resistor power rating: P > (Vs - Vz) × Imax

Example: output voltage required is 5V, output current required is 60mA.

1. Vz = 4.7V (nearest value available)
2. Vs = 8V (it must be a few volts greater than Vz)
3. Imax = 66mA (output current plus 10%)
4. Pz > 4.7V × 66mA = 310mW, choose Pz = 400mW
5. R = (8V - 4.7V) / 66mA = 0.05kohm = 50ohm, choose R = 47ohm
6. Resistor power rating P > (8V - 4.7V) × 66mA = 218mW, choose P = 0.5W


zener diode
a = anode, k = cathode

Smoothing DC (Direct Current)

Smoothing is performed by a large value electrolytic capacitor (polorised capasitor) connected across the DC supply to act as a reservoir, supplying current to the output when the varying DC voltage from the rectifier is falling. The diagram shows the unsmoothed varying DC (dotted line) and the smoothed DC (solid line). The capacitor charges quickly near the peak of the varying DC, and then discharges as it supplies current to the output.



Note that smoothing significantly increases the average DC voltage to almost the peak value (1.4 × RMS value). For example 6V RMS AC is rectified to full wave DC of about 4.6V RMS (1.4V is lost in the bridge rectifier), with smoothing this increases to almost the peak value giving 1.4 × 4.6 = 6.4V smooth DC.

Smoothing is not perfect due to the capacitor voltage falling a little as it discharges, giving a small ripple voltage. For many circuits a ripple which is 10% of the supply voltage is satisfactory and the equation below gives the required value for the smoothing capacitor. A larger capacitor will give less ripple. The capacitor value must be doubled when smoothing half-wave DC.

Smoothing capacitor for 10% ripple, C = 5 × Io
Vs × f

C = smoothing capacitance in farads (F)
Io = output current from the supply in amps (A)
Vs = supply voltage in volts (V), this is the peak value of the unsmoothed DC
f = frequency of the AC supply in hertz (Hz), 50Hz in the UK

Rectifier

There are several ways of connecting diodes to make a rectifier to convert AC to DC. The bridge rectifier is the most important and it produces full-wave varying DC. A full-wave rectifier can also be made from just two diodes if a centre-tap transformer is used, but this method is rarely used now that diodes are cheaper. A single diode can be used as a rectifier but it only uses the positive (+) parts of the AC wave to produce half-wave varying DC.

Bridge rectifier
A bridge rectifier can be made using four individual diodes, but it is also available in special packages containing the four diodes required. It is called a full-wave rectifier because it uses all the AC wave (both positive and negative sections). 1.4V is used up in the bridge rectifier because each diode uses 0.7V when conducting and there are always two diodes conducting, as shown in the diagram below. Bridge rectifiers are rated by the maximum current they can pass and the maximum reverse voltage they can withstand (this must be at least three times the supply RMS voltage so the rectifier can withstand the peak voltages). Please see the Diodes page for more details, including pictures of bridge rectifiers.



Bridge rectifier
Alternate pairs of diodes conduct, changing over
the connections so the alternating directions of
AC are converted to the one direction of DC.



Output: full-wave varying DC
(using all the AC wave)

Single diode rectifier
A single diode can be used as a rectifier but this produces half-wave varying DC which has gaps when the AC is negative. It is hard to smooth this sufficiently well to supply electronic circuits unless they require a very small current so the smoothing capacitor does not significantly discharge during the gaps. Please see the Diodes page for some examples of rectifier diodes.



Single diode rectifier



Output: half-wave varying DC
(using only half the AC wave)

Transformer

Transformers convert AC electricity from one voltage to another with little loss of power. Transformers work only with AC and this is one of the reasons why mains electricity is AC.

Step-up transformers increase voltage, step-down transformers reduce voltage. Most power supplies use a step-down transformer to reduce the dangerously high mains voltage (230V in UK and 240W in Malaysia) to a safer low voltage.

The input coil is called the primary and the output coil is called the secondary. There is no electrical connection between the two coils, instead they are linked by an alternating magnetic field created in the soft-iron core of the transformer. The two lines in the middle of the circuit symbol represent the core.

Transformers waste very little power so the power out is (almost) equal to the power in. Note that as voltage is stepped down current is stepped up.

The ratio of the number of turns on each coil, called the turns ratio, determines the ratio of the voltages. A step-down transformer has a large number of turns on its primary (input) coil which is connected to the high voltage mains supply, and a small number of turns on its secondary (output) coil to give a low output voltage.

turns ratio = Vp = Np and power out = power in
Vs Ns Vs × Is = Vp × Ip

Vp = primary (input) voltage
Np = number of turns on primary coil
Ip = primary (input) current Vs = secondary (output) voltage
Ns = number of turns on secondary coil
Is = secondary (output) current



September 13 2009 - Activity

Sunday, September 13, 2009

Type of Diodes

Diodes can be classified by the functions of the circuit in which it is being used, or more commonly, by the shape that is demanded by the size of the products in which it will be mounted. The complicated point is that there is no direct relation between the two and you must keep them both in your mind at all times. However, you can think of the function as the base, and since this function can then be supported by many different shapes, it can then be further classified by those shapes.

Zener diode (constant voltage diode)
Since a Zener diode generates a constant voltage from the Zener effect that occurs when a reverse bias voltage is applied, it is also called a constant voltage diode. By using the resulting constant voltage, it can be used in constant voltage circuits and other circuits that require a reference voltage.

Schottky barrier diode
A Schottky barrier diode attaches a Schottky gate electrode directly to a n-type semiconductor and makes use of the fact that reverse bias voltages are prevented from causing current flow across the junction of the metal and semiconductor. Some are for high frequencies and some are for general rectification. Those for high frequencies are often used in high-speed switching for wave detectors and mixers in the UHF and microwave bands. Since the forward voltage is small and the reverse breakdown voltage cannot be made too high (currently, approx. 100 to 200 volts) compared to normal diodes for general rectification, Schottky barrier diodes for general rectification are used for the rectification of power supplies for low voltages and high currents, or power supply switching for the rectification of high frequencies with its small reverse recovery time.
Switching diode
By using the rectifying properties of the pn junction (the extreme difference in the forward and reverse bias resistances), these diodes are mainly used for switching the circuit on and off. Generally, when you speak of switching diodes, it includes Schottky barrier diodes and band switching diodes, but we at Rohm think of them as separate types. Switching diodes are the normal silicon small-signal switching diodes. They are used for demodulation, modulation, switching, mixing, and the like and make up approximately half of the total diodes produced in Japan. Rohm holds the largest share of this market.

Rectifier diodes
In general, these diodes are aimed at current rectification for currents of 1 ampere or more and are used in rectification circuits for power supplies. There are many types from low power to high power with a wide range of different packages. The most common type is the low power 1 ampere class that makes up approximately 70% of the rectifier diodes produced.

Band switching diodes

The band switching diode was developed as a general small signal diode for high frequency use. Since it is used for switching the frequency bands for high frequency tuners, the resistance at high frequencies is small and the capacitance between the electrodes is kept as small as possible.

Monsters, Inc.

Friday, September 11, 2009

It's been several years since Pixar first wowed us with "Toy Story", the first three-dimensional cartoon ever produced. Now we know it as the re-shaping of the animation world as this year alone we have had three 3-D animated films hit the big screen. One of those was the movie "Shrek" an insanely funny animated work from Dreamworks that so far ranks as the funniest movie of the year. Pixar hopes to stand up right next to the giant ogre this weekend with "Monsters Inc", a delightful family film that sadly just falls short of that achievement, but is still worth the trip.

One of the reasons why is for the inventive ideas the story comes up with. It takes place in the city known as Monstropolis, a haven for monsters, which is all powered by the power plant, commonly known as Monsters Incorporated.

The company consists mainly of frightening children, storing their screams, and then later powering the city with them. The number one scarer in the biz is John P. Sullivan, or Sully, (voiced by John Goodman), a hairy, six foot, and blue working class monster with a good heart, but also a real knack for his work. His partner is the always fast talking Mike Wazowski (voiced by Billy Crystal), who is both friend and trainer to Sully.

The two of them are very excited for the reason that Sully is about to break the all time scare record. But one monster that stands in there way is Randall Boggs (voiced as evil as ever by Steve Buscemi), a chameleon-like creature who finally decides to resort to cheating when Sully remains at the top of the standings board at the end of the day.

The company uses an assembly line of closet doors to get to the human world, just they are to be locked away at the end of the day. But when Sully goes back to the office to pick up something for Mike, he sees a door left out, and a little human girl pulling at his fur. A monster touching a human or a human getting through the doors is considered to be a contamination alert, so Sully can do nothing but panic when he sees her.

Soon the entire city is looking for the monsters hiding the little girl, and both Sully and Mike each have to think of a plan before this ruins them both.

"Monsters Inc" is loaded with creative ideas, from the plot all the way down to the objects and animals used as inspirations for each monster. Each character is weird looking in their own way and all of them have personalities that are colorful enough to be entertained by. Billy Crystal's Mike Wazowski is easily the most energetic character in the film, and thus the most entertaining.

Only the main problem I had with the movie is the lack of comedy it is able to create. There are a couple of belly laughs and a handful of sight gags, but there is a big gap between all of them that could seriously use some of that witty dialogue that worked so well in last year's Disney film, "The Emperor's New Groove".

But "Monsters Inc" makes up for a lack of comedy by adding a lot of excitement (the finale features one of the best chase sequences I've seen from a Disney film), and some really touching moments that both parents and kids will like. If you're looking for a family film that's interesting and fun, then "Monsters Inc." will do just fine for the time being.

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Finding Nemo


Actors: Starring the voices of: Albert Brooks, Ellen DeGeneres, William Dafoe, Geoffrey Rush, Allison Janney, Barry Humphries, Brad Garrett, Austin Pendleton, Stephen Root, Vicki Lewis, Joe Ranft, John Ratzenberger, Alexander Gould, Elizabeth Perkins

Director: Andrew Stanton

Special Notes: Here are a couple of fishy fun facts to know -- did you know that 71 percent of the earth is covered by water and that there are 3.7 trillion fish that live in then ocean?

Plot: Marlin (Brooks) is an overly cautious clownfish who lives in the beautiful tropical waters of the Great Barrier Reef. Marlin lives a safe and secluded life with his only son Nemo (Gould), warning him about the dangerous world beyond. But like all young fish, Nemo is eager to explore the mysterious reef surrounding his home and the world beyond. One day, when Nemo knows better, he swims outside the safety of his father and unexpectedly is "fish-napped" and taken far from home. Nemo is placed in a fish tank in a dentist's office and quickly makes friends, but he longs for his father. Meanwhile back at the reef, Marlin has to face his fears and venture out to find his son. On his journey, Marlin's joined by a Regal blue tang fish named Dory (DeGeneres) who has a bad short-term memory but a big heart. As the two search for Nemo, they encounter all sorts of obstacles (hungry seabirds, sewer systems, man) and plenty of new friends and foes [Gill (Dafoe), Bloat (Garrett), Peach (Janney) and Nigel (Rush)], as gradually, Marlin becomes a hero in the eyes of his son.

Good: Hurray for another winner from the folks who brought us "Toy Story", "A Bug's Life" and "Monsters Inc."! Get ready for a new world of computer-animation that is not only breathtakingly beautiful to behold, but will spoil young and old alike with a new standard of animation. The movie's simple but clever premise may be as old as parents' advice, but it still makes for a funny, entertaining and realistic story dealing with issues that parents go through on an everyday basis with their kids (Marlin wants his son to be proud of him despite his fears, Nemo is disobedient and has to deal with going to school for the first time, etc.). Parents, there are several topics that will make for interesting discussions afterwards. This is one of those refreshing stories with a perfectly cast ensemble that definitely has the "awww" factor going for it. DeGeneres is delightful as the forgetful but faithful companion that gently coaxes the overly cautious Brook's to find his son. The witty one-liners and quick-witted script will entertain the mature crowd, while the beautiful colors and catchy score will mesmerize the little ones. In a summer when intense action adventure heroes (and sequels) are dominating the box office, it's nice to see Disney and Pixar come through with another example or fabulous family-friendly entertainment at it's best!

Bad: I can't imagine little ones being scared by this movie, but there are a couple of scenes with creepy looking fish that scare and then chase Marlin and Dory. If I was a kid, I think Bruce the shark would bother me the most.

Bottom Line: Just when you think it's safe to go back into the water … Disney and Pixar make it unforgettable and fun as well. Not only are the underwater scenes brilliant and fascinating, but the adventures on dry land prove to be challenging (rescuing Nemo from a dentist's office) and intense as well. You'll LOVE the ending! I have to admit … I enjoyed DeGeneres in this movie! Not only is her voice perfect for the part, but she's hilarious with her delivery as well. Never again will you look at an aquarium as a "fish tank" or the ocean as simply a place to go fishing!

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Who Am I


Jackie Chan, a top secret militant soldier, crashes into the South African jungle after his mission of kidnapping three scientists (who were experimenting with a powerful mineral) has gone array. Waking up in a village of local natives, Chan has no memory of who he is, thus being addressed as "Who Am I". His journey with aid from two female sidekicks to find out his identity leads him all the way to Rotterdam where he coincidentally discovers the location of the organization that kidnapped the three scientists. With no memory, Chan is thirsty for answers by any means necessary.

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Underworld


Vampires and Werewolves have been sworn enemies for hundreds of years. Now fought in a Gothic-like setting, the conflict takes an unexpected and deadly new turn. Selene, a beautiful vampire warrior, uncovers a Lycan plot that could prove fatal for her entire race. She shadows a human, Michael, the Lycan's supposed target. Although she finds herself becoming attracted to him, he becomes infected with the lupine disease during a violent struggle with the Lycan overlord, Lucian, long thought to be dead. Now both sides must decide how to end the conflict and save their species as new and terrifying secrets unearth themselves and threaten their entire existance.

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Kuch Kuch Hota Hai


Rahul and Anjali are students in a college in India, while Anjali is attracted to him, he only treats her as a close friend. Unable to tell him about her feelings, Rahul meets and gets married to another Indian girl by the name of Tina. Anjali decides not to get married. Rahul and his wife lead a blissful life, and soon Tina gets pregnant. She gives birth to a baby girl, they name her Anjali, but shortly after that Tina dies, leaving Rahul alone to look after Tina. He does a fairly good job at this, and Anjali grows up in his care. Then Anjali comes to know about the older Anjali, and her love for her dad, and sets forth on the task of bringing them together, unsure if her dad will even accept any other woman to take his late wife's place.

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10 Things I Hate About You



Adapted from William Shakespeare's play "The Taming of the Shrew," 10 Things I Hate About You starts off with Cameron, new student at Padua High, sitting in the office of the quirky guidance counselor Ms. Perky. He is then shown around the school by Michael, who will become his best friend. During his tour is when Cameron first sees Bianca Stratford, a beautiful sophomore with one problem: she isn't allowed to date. And neither is her "shrew" sister, Katarina, a senior who loves indie rock and feminist prose and hates conformity. But Kat and Bianca's father alter's his house rule: now, Bianca can date... as long as Kat has a date, too. Now, in order for Cameron to date Bianca, he has to find someone to date Kat. So Michael helps him enlist the help of pretty-boy/jerk/model Joey Donner, tricking him into thinking that *he* will get to take Bianca out if he pays someone to take out Kat. His choice: Patrick Verona, a bad-boy with a mysterious reputation--some say he ate a live duck once, others that he lit a state trooper on fire, and even more claim that he had a brief porn career. Will Patrick win Kat's heart? Will Cameron win Bianca's? Or will everything hit the fan...?

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The Princess Diaries



A socially awkward but very bright 15-year-old girl being raised by a single mom discovers that she is the princess of a small European country because of the recent death of her long-absent father, who, unknown to her, was the crown prince of Genovia. She must make a choice between continuing the life of a San Francisco teen or stepping up to the throne. While Mia makes up her mind, she's pressed into taking princess lessons from her grandmother.

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September 10 2009 - Activity

Thursday, September 10, 2009