Replacing the Hard Disk

21 October 2008

After having scanned the harddisk using CHKDSK, the computer showed multiple error messages of “CHKDSK is performing additional checking or recovery…”. After having booted up the computer to backup the files, one received error messages.

What Could Have Gone Wrong?CHKDSK could have found bad sectors in the hard disk and making attempts to recover the bad sectors. This process usually takes less than 30 minutes. If the process takes hours with more than 20 error messages, one might have a faulty harddisk.

What should I do Next?
Back up as many files as possible. There might still be a chance that one could recover all the files if one can still boot up the computer. If one could not boot up the computer, try to repair the master boot sectors and the boot files. If the computer failed to start up after this, go and seek other solutions. One of the solution is to isolate the faulty section of the harddisk; the other solution is to repalce the harddisk. This article will describe the latter.

What do I need?
a) A copy of the XP installation disk
b) Another good harddisk of similar or bigger capacity

Why Not Use Existing Harddrive?
Unless one is sure about the condition of the harddisk, it is advisable to backup the files into another harddisk. Not only the existing harddisk might not have the necessary capacity, but also, the backing up operation might cause more damages to the harddisk.


Step by Step
1. Hooking up the new harddisk

• Switch off the computer and hook up the new harddisk as a slave drive
• Start up the computer and boot up the computer as usual
• Mount the new harddisk using available software such as Disk Manager or Partition Magic and Format the new harddisk

Mount the new harddisk with 2 partitions; one of them preferably with large enough capacity and formatted with NTFS system. This is because the normal FAT32 system has a limited capacity of 4 GB using the XP’s backup program.
2. Backing up the System/Program
If one has not backup the system/program before, should start to do so now. Back up as many programs as you can with priority giving to the following files
a) System state. This will restore your computer to its original condition
b) Important data, such as stock data, JPG, photos
c) Hard to get programs in “Program file”
d) One should also backup the necessary windows' drivers as one would have to install a new copy of the XP system on the new harddisk. This program can be used to extract drivers on the existing XP operating system.

Tips:

• Try to backup directory by directory. If there are error message, then select to backup sub-directory by sub-directory or file by file.
• Some program stores information in program/common file folder as well as in document and setting folder. When in doubt, try to backup as many files/directories as possible.
• Place the backup files in the new hard disk.
• If the backup file size is more than 4 GB, store the file in a NTFS partition
• Select to verify the data whenever possible.
• A lot to time and patient

3. Restoring the System/Program

• With the computer switched off, dismount the old harddisk and hook the new harddisk as the master drive.
• Reboot using XP installation disk
• Install new XP operating system in the new harddisk. Use the same username as the old copy of XP system when ask to create one

If everything is fine, restore all the backup files, one by one, starting in reverse sequent (though not important) as stated in

Why Not all the Menu Icons were shown?The restore should reinstate the computer to its original condition. If one has problem with missing icons in the menu, this could probably due to:

a) The username during XP installation is not the same as those in the old harddisk or the backup files
Check if there are more than one username folders in the “Documents and Settings” of the C: drive. Find the original username folder and check the sub folder , “C:\Documents and Settings\UserName\Desktop “ (username= your username) to see if it contains the menu icons that you have expected; if so, copy all the files/directories in this desktop folder over to the default username folder.

b) Some programs were not backed up properly
The programs or part of the program component could be missing.


Can One Re-Use the Old Harddisk?If one can boot up the computer, probably the damage in the hard disk are not as serious. If one want to reuse this faulty harddisk, one should

a) Try to re-run the CHKDSK again just to make sure that it has cleared all the bad sectors;
b) Clean the harddisk using the clean manager of XP system;
c) Defrag the disk, if possible in SAFEMODE

If everything else failed, one could always revive the harddisk .

Related Articles
1. How to Revive Faulty Hard Disk
1. Repair Damage Master Boot Record & Boot Sectors

How To Restart After Computer Hangs

17 October 2008

IntroductionThe computer just hanged. This article will try to offer some help step by step.

What can be wrong?
Restart the computer. If one can hear a soft and short beep sound, most likely the computer's hardware is working fine. The master boot record or boot files or the Registry of the XP's operating system may be corrupted.

What are the Usual Ways?
Usually, users will re-install the complete XP system. Some will choose to reformat the hard disk. One would lose all the personal documents, program files and other 3rd party programs. This article will describe a method that will not only save time for the restoration but also avoid having to reinstall all other programs.

What's Required?
a) A good working hard disk;
b) XP installation disk

How to?
Step 1 Suspect Faulty Master Boot Record or the Boot Files Follow the instructions in this article to repair the master boot record and the boot files and restart the computer. If the computer still hangs, then

Step 2 Suspect Faulty RegistryCopy the 5 files, namely: system, security, software, sam and default files from the “repair” sub folder to “config” sub folder in Windows and restart the computer to enter the safe mode. This Microsoft site gives the detailed instructions.

Thereafter:

a) If you have a Registry Backup copyFollowing this article to restore the Registry files from the backup copy and restart

b) If you do not have a Registry Backup Copy
Continue to follow the instructions given by Microsoft and restore the 5 files from a special “System Volume Information” folder. This folder is normally hidden from view. The system files are stored in this special folder when XP's System Restore is working. Note that the files in the folder may contain viruses as System Restore does not check for viruses when it stores the files.

Related articles
1. How to Restore Corrupted Registry
2. How to backup and restore Registry files
3, How to repair faulty Master Boot Record and Boot files

Back Up XP Registry and Boot Files

17 October 2008
Introduction
Viruses often attack the Registry of the computer’s operating system. After that, the viruses would be loaded to take control when the user starts the computer. This article will describe how we can back up a copy of the Registry and have it restored at a later date.

What is Registry and How Viruses Can attack it ?
Registry is a place where XP keeps all the information about the computer's hardware and software. It is being used by all the parties including 3rd party hardware and software. For example, if a new program has just been installed or files added, the Registry will be updated. Therefore, the Registry is the one place where it is most vulnerable to virus attacks. It is often difficult to get rid of them; sometimes, they may modify the Registry, making computers going hire-wired.
Viruses can be loaded into the Registry when we browse the Internet or when we run a program.
We can always restore the computer back to its earlier saved state if we have a backup copy.

How to Backup the Registry?
There are 3 methods:

Method 1: Using the System RestoreThis is part of the XP built-in program and can be set to save a copy of the Registry automatically or as and when required. Read this article.

Method 2: Backing up the whole of the Registry
Do this often manually or whenever we make some changes to the computer.

• Click Start, and then click Run. One will reach the following screen.
• In the drop down box, type "regedit"(without quotes), and then click OK

• In the next screen, select “My Computer” and in the File menu, click Export.

• In the "Save in" box, select a location where you want to save the Registry
• In the "File name" box, type a file name, and then click Save.

Note
1. This file will have an extension of ".reg" and is at least 5 Mbytes.
2. Make sure the computer is cleaned of viruses before saving.
3. Use separate file name each time as the copy of Registry to be saved could contain viruses.
4. Save this file in another hard drive or thumb drive or a RW CD ROM
Method 3: Backing up the System state
XP operating system has a built-in function called “Backup” in the System Tools folder. One can back up not only the whole registry but also the boot files in the Windows’ system 32 folder and the COM+ Class Registration Database.

• In the main Window, click Start, then in the All program/Accessories/System Tool folder, start the Backup program and follow the instructions, one should reach this screen

• Browse and select where the backup file should be installed and give the backup file a file name. Remember to use different file names if necessary. Click Next and one should reach the following screen.

• Select "Let me choose what to backup" and click Next to reach the following screen.

• Now, expand My Computer folder and then click the tick box next to "System State" folder as shown and click Next
• Select Advance button and after that, select "Normal" in dropdown box. Click next and one would reach the following screen to select the verification of file after backup. Tick that verification box and then Next. The computer will do the rest of job.
  
  
  Note
  1. One would need a free disk space of about 600 MB.
  2. Make sure the computer is cleaned of viruses before saving
  3. Store the backup file in a thumbdrive or RW CD or another harddisk so that it can be read and the backup file restored in case of harddisk failures.
  4. The backup file has a maximum limit of 4 GB for hard disk with FAT32 system rather than NTFS system. Check your system here.
  5. BACKUP is not installed by default in Windows XP Home Edition. Install it using the instructions available at: Q302894. A copy of Backup program can be downloaded here. Restoring the backup files
  To restore any Registry, always try to boot into the SAFE Mode. This will start the computer with minimum numbers of file and prevent viruses from loading.
  To boot into SAFE Mode, hit F8 continuously after the 1st welcome screen when one boots up the computer.
  When one is in the SAFE mode screen, might as well try if one could start the computer using the option "using Last Known Good Configuration".
  Method 1: Using System RestoreRefer to this article
  Method 2: Restore the whole of the Registry
  Go to the directory or the folder where the registry file was stored. Double click that file. The following screen will appear. Click OK
  
  Method 3: Restore the System state
  
  • Following Step 1 of method 3 in the backup section above, then choose "restore files and settings" instead, one should reach the following screen.
  
  
  • Browse through to the directory of the backup file and doubleclick the file, a new screen should show the folder "System State".
  • Tick the box to select file to restore and click Next. Click advance in the next screen. Change the default setting if necessary.
  Which of the 3 Methods is the Best?
  Method 3 appears to be the best; however, there were reports that it may not be compatible with some 3rd party software and may not restore everything in full. Sometime, it prompted users for CD keys etc after the restore.
  Method 2 is neat as it restores everything in full but it does not back up the boot file and Com+ file
  Method 1 is often the target of viruses. Very often, it would automatically save a copy of Registry complete with viruses. Some experts therefore recommended to de-activate the auto-saving function. To de-activate this function, just click start and the run in the main Windows and in the dropdown box, enter "sysdm.cpl" (without quotes). Then in the System Properties window, select the System Restore tab to untick box to turn off the system restore function.
  It is good to use all the 3 methods.

Related Articles
1. How To Restart After Computer Hangs

Fundamentals of Some STI Counters

The table (click the dates) will show the fundamentals such as shareholders' fund, long term debts, liquidity ratio and other financial data of about 200 counters in STI. It will be published once by the end of every month when most companies have reported its earnings. If there are additional counters to be included, please email skyjuicetse@yahoo.com.sg

1. 16 October 2008
2. 30 November 2008 30 November 2008(interactive-see note)

Disclaimer:
Information here is for sharing and learning. It is not intended to give any advice on any stock or movement or trend of any index. If a price or movment of a stock/index is given, it is only intended for illustration. The reader shall verify the information given here before using them.

Note: To use the interactive mode, one would need to download a add-in component for internet explorer from Microsoft website and one must also have Microsoft Excel 2003.

Forward and Swap Fuel Oil Prices

11 October 2008

Introduction

What is forward fuel oil price? What is swap fuel oil prices? How do they differ? Are there confusions in using the term "forward fuel oil prices" by the Energy Market Authority of Singapore (EMA)? What is the fair price to be used for evaluating electricity rates?

What is Forward and Swap Fuel Oil Prices?

They are just derivatives of oil trades similar to the Futures Oil prices traded in the New York Mercantile Exchange (NYMEX).

Forward fuel oil prices (FFOP) are quoted in a forward market. Unlike the NYMEX Futures market, the forward market is less price transparent because the forward contracts are traded informally between principals such as big oil companies who are not obliged to publish the details of any deal that is done.

Swap fuel oil prices (SFOP) are quoted in a swap market. It is a relatively new form of OTC derivative trading market. It is very much like the NYMEX Futures except it is commonly used by banks & big oil companies nowadays; hence, big quantities with relatively few trades. The oil trades are quoted in metric tonnes instead of barrels. Like FFOP, it is still a private agreement between two parties to exchange cash at pre-arranged dates in the future according to an agreed price formula. But unlike FFOP, the SFOP quotations can be found in public exchanges such as ICE; also, SFOP does not involve physically delivery of fuel oil at the end of the contract. More details about FFOP and SFOP can be found here.

Confused Terms Used
The EMA's website clearly shows that EMA has been using the term Forward Fuel Oil Price (FFOP) for evaluating the electricity rate. This term is also being used by EMA in all its clarifications in the press and newspapers. But if one clicks the link on FFOP in EMA's website, one will be led to a published SWAP quotation from ICE. Is EMA confused between the terms used?

Click for enlarged view

Click for enlarged view

The ICE's Quotation

The ICE's quotation for 4th quarter 2008 which is quoted in July 2008 is shown attached. They are quoted in US$ per metric tonne. To convert from metric tonne to numbers of oil barrel, one would have to divide it by 6.6.

Click for enlarged view

The quotation clearly shows that there are not more than 300 bids/offers and 11 deals were settled in the month of July 2008. The highest quote was US$ 795 per metric tonne (or US$ 120 per barrel) and the lowest quote was US$ 698 (or US$ 105 per barrel).

Which Market is Fair?
There just isn't a market price that can be used to accurately predict the fuel oil price to be used in the future. This is because NYMEX futures, forward, swap, options are all derivative instruments of the spot oil market. They are only good for use as hedging tools. They are all subject to manipulation, in particular, the FFOP and SFOP because of the private dealings and the small numbers of active trades.

Among the markets, NYMEX futures is the most transparent and most actively traded; therefore, a better market. Alternatively, we can use spot fuel oil price.

SP & Power Generating Companies would never lose out in any pricing that EMA has adopted and agreed upon. This is because SP & Power Generating Companies have the means to hedge such price against any future price variation like what SIA has been doing all the while.

If EMA wanted to be fair to both SP & Power Generating Companies and the consumers, they could always do a price adjustment at the end of a period, like the Public Utilities Board (PUB) used to before 2000. Using SFOP or FFOP to evaluate the electricity rate is not necessary fair to the consumers.

Other related Articles

1. Forward Fuel Oil Pricing Used by EMA

2. Is it fair to use Forward Fuel Oil Pricing

Biggest Fall in DOW in a Week?

10 October 2008

DOW fell another 678 points in 9 October 2008 or about 7.4%. This makes the total fall to be more than 20% in 7 trading days, from 1 October to 9 October 2008 or about 1 week. Is this the biggest fall in DOW's history?

Doubleclick for enlarged picture
Comparable Falls
There are 2 occasions where DOW fell for about 20% or more in 1 week.
1st Fall
The first was from 9 October 1987 to 19 October 1987. DOW fell from 2,516 to 1,738, a total of 778 points or more than 30%. That day on 19 October, the famous Black Monday, DOW registered the biggest fall of 22% in a single day. The market did not recover from this damage until 01 August 1989, about 2 years after the fall.

Doubleclick for enlarged picture2nd Fall
The second was from 13 May 1940 to 21 May 1940. DOW fell from 144 to 114 or about 30 points or about 21%. The market did not recover until 15 July 1943 or about 3 years later. This was in the midst of 2nd World War.

Doubleclick for enlarged picture

The Biggest Fall
The biggest fall in the history of DOW has to be the fall during the great depression in 1932. Although this is not the biggest fall in a week, DOW fell by about 50% over a period of about 2 years. The market did not fully recovered until 1953 or about 20 years later.

Forward Fuel Price ; Is it Fair?

8 October 2008

Introduction
EMA used forward fuel oil pricing (FFOP) quoted in July 08 for the next 3 months to peg electricity rate in Singapore; as a result, the electricity rate went up by 21%. This article will examine if this FFOP is a fair peg.

What is Forward Fuel Oil Price(FFOP)?
FFOP is quoted in a forward market just like the Futures market in New York Mercantile Exchange (NYMEX). But unlike the Futures market, the forward market is less price transparent because the forward contracts are traded informally between principals such as big oil companies who are not obliged to publish the details of any deal that is done. For more details about forward fuel oil contracts, please refer to this article.

Why the High FFOP?
EMA explained that the FFOP quoted in July 08 for delivery of fuel oil between October 08 and December 08 is being used to determine the electricity rate for this period. As the fuel oil price increased sharply in July this year, there was a corresponding spike in the July forward fuel oil price for October 08 until December 08. This appears on the surface to be very fair to both the Power Generating Companies as well as the consumers.

Why July's FFOP Not Reflective?
Rightly speaking, if fuel delivery is for period between October 08 and December 08, it should reflect the present fuel oil price; however, this is never the case. Lets examine the oil prices quoted in the NYMEX (FFOP is not available) for delivery in Feb 09 and for delivery in Nov 08. One could immediately identify that these 2 quotes are almost identical.

Doubleclick for enlarged picture

Doubleclick for enlarged picture

Why So Identical ?
This is because the Oil Price for future delivery is always affected by the prevailing spot price. When the traders do not know what is in stored for them in the future, they would invariably use the present spot price as the base price.

What's the Implication?
The FFOP quoted 3 months ago will be forever lagging behind the spot or the present fuel oil price. If the oil price continues to climb, the electricity rate will become very reasonable; on the other hand, the electricity rate would become very unreasonable if the oil price continues to fall.

Is It Fair to Use FFOP?
On the surface, it would appear very fair to use FFOP to peg electricity rate because SP and the Power Generating Companies will take actual delivery of the fuel oil at the end of the period. On further examination, it would appear to be unfair to the consumer because:-

a) This FFOP rate is less transparent; for example, the NYMEX Futures for oil was quoted at US $ 147 per barrel at the peak of July 08 whereas the FFOP used to peg the electricity rate was quoted as US $ 155 per barrel. Whether the FFOP deal in July 08 was done at its peak is not known publicly;

b) FFOP contracts can be traded in the market. If SP and Power Generating Companies found advantages to trade the contracts, they can do so and buy cheaper oil from the spot market;

c) It is very common for oil consumption companies, such as airlines and power generating companies to hedge present fuel oil price against any future price variation. For example, SIA has been known to hedge its jet fuel oil price. With the correct hedge, they will never lose out and might even gain handsome profits. On the other hand, the consumers will never have any choice but the pay for the electricity rate.

Conclusion
The FFOP as a peg for electricity rate does not seem to be fair to the consumers who have no alternative but to pay for the electrcity rate.

Afternote:

1. EMA was referring to SWAP fuel oil pricing as Forward Fuel Oil pricing

2. The USD 155 per barrel should be read as SGD 155 per barrel

Related Articles

1. Confusion in the use of Forward and Swap Fuel Oil Pricing
2. Forward Fuel Oil Pricing Used By EMA

Refrigerator Repair

1 December 2009

Repairing RefrigeratorsRefrigerator is one of the most common household equipment. This article will give some tips on how to locate and repair some common faults in refrigerators

What are the common faultsModern refrigerators need little or no maintenance except for the regular cleaning of blocked ventilation holes if it is located in a dirty environment. Poor cooling is often caused by faulty or aged components. One of the common fault is frozen cooling coils. Other faults can be motor related; for example, motor starter problem. Because the refrigerant system is a total sealed system, leakage of refrigerant is not usually the problem.


How to Check if the Fridge is Working Properly
A working fridge should:

1) Feel warm on some part of the panel. This is because fridge uses these panel to dissipate heat;

2) Have noise coming out of the electric motor;

If the fridge panel is always cold or there is no running motor noise for a long period, most likely the fridge is dead; otherwise, it could be due to the following problems:

a) Frozen cooling coils
b) Faulty components

This article will concentrate on how to clear frozen cooling coils

Frozen Cooling Coils

Frozen cooling coils could happen under 2 conditions:-

a) Refrigerator is short of freon gas;
b) Faulty defrosting circuits

Like any refrigeration equipment, coils are easily frozen when there is a shortage of freon gas in the system. However, this is quite unlikely in the case of refrigerators because most refrigeration system is sealed and there is little chance for freon leakage. When the coil is frozen, it will not allow air to pass through the colling coil and hence, cooling is affected.

Checks for Frozen Cooling CoilsModern refrigerators are frost free. Cooling is achieved by a circulating fan and defrosting is done by a defrosting heater.





Because the cooling coil and the fan are hidden from view, visual inspection is often not possible. However, one could deduce if the coil is frozen by checking if the compressor is working and also by observing if defroster is functioning.

How to CheckStep a) Check if the defroster is working
If the refrigerator has a defrosting tray underneath, check the tray for some water. The defrosting heaters will be turned on automatically once a day by a self running time, during which, ice if any on the cooling coil will be drained to the defrosting tray.

For refrigerator that has concealed defrosting tray, then the only way to check if the defroster is working is to turn off the refrigerator for more than 1 hour, allowing ice to be defrosted. If by turning on the refrigerator resume the cooling function, one can confirm that the defroster circuit is faulty; then, proceed to step c);
Important Note: The compressor panel consist of electrical components. Proceed to step b) & c) when you know what you are doing.
Step b): Check if the compressor is working properly
1) Open up the compressor chamber by removing the back panel of the refrigerator;

2) Check for oil leakages in the refrigerator pipe and tube; if there are traces of oil anywhere, most likely the system have a freon leak;

3) Check if the compressor motor is running. If it is running, check for its proper working by hand feeling the temperature of the compressor's discharged and the suction tubes. One should notice the discharged tube is always warm and suction tube is always cool. If there is not much temperature difference, most likely the compressor is not working properly and it is time to change the refrigerator.

Step c)
The defrosting components normally consist of a timer and a few heaters. Check the heater circuit for fault using an ohm meter. If the heaters are ok, most likely the timer is fault. Repair or replace the timer.

The Foward Fuel Oil Price Used by EMA

5 October 2008

Introduction
The Energy Market Authority (EMA) recently announced that our electricity rate would increase by 21%, the highest one-time increase in seven to eight years. This is because EMA has pegged the electricity rate to the forward fuel oil pricing for the next 3 months.

EMA’s Explanation for the Price Hike
EMA, the electricity and gas industry regulator, explained that since 2004, electricity tariffs had been pegged to the "forward fuel oil prices" for the next three months. This price was $155.14 per barrel, up 38 per cent from $112.35 per barrel for the current quarter.

What is “Forward Fuel Oil Price” ?
There are about 4 types of oil market:
a) The Spot market
b) The forward market
c) The Futures market
d) The Swap and options market

More information about the various oil markets can be found here
There are also more about futures and forward contracts in here and here.

Forward contracts are traded in the forward market. Like the futures contracts, forward fuel oil contracts are traded for the delivery of fuel oil on a future date at a pre-agreed price; but unlike futures contracts, the forward contracts are traded informally between principals such as big oil companies who are not obliged to publish the details of any deal that is done. The forward market has therefore lesser price transparency than a futures market such as NYMEX Oil Futures traded in the US.
Deals in forward contracts are usually done over the telephone. Participants either trade directly between each other or through specialist brokers (like Goldman Sachs) who provide a useful service by quoting bid-ask levels for forward Contracts. The main difference between forward and futures trading is as shown in the following table:
Why EMA used Forward Pricing of Fuel Oil?
EMA explained that “forward fuel oil” prices are the prices of fuel delivered to the Power Generating Companies; also, they are less volatile than the 'spot oil' prices quoted for immediate deliveries. To illustrate, EMA used the following graph:-

While there is no way to verify the authenticity of the forward fuel oil prices quoted by EMA, the following 2 curves in this article about forward contracts of West Texas Intermediate (WTI) and Brent will illustrate that forward pricing can also be very volatile.

Correct for EMA to use Forward Pricing?
Forward pricing, like future pricing, is often used as a hedge against any future price variation . If it is used for other purpose, it can act as a double-edged sword, working for as well as against an investor. In this case, as a peg for electricity rate for the next 3 months, it will work for consumers if the oil price is rising and against the consumers if the oil price is falling. Furthermore, EMA uses forward fuel oil pricing quoted 3 months ago, it is forever lagging months behind the actual fuel oil prices.

Forward pricing is less transparent as spot pricing. To protect the interest of the consumers, it would be better to use the spot or futures pricings that are traded in public exchanges such as NYMEX.

Will SP & Power Generating Companies lose?
SP and Power Generating Companies will not lose out with any price set by EMA if the set price has been agreed upon. This is because SP and Power Generating Companies can always hedge against any future fuel oil price variations. SIA's hedging policy on jet fuel price is one of the good examples. On the other hand, if consumers were to be asked to pay higher fuel price today for the next 3 months and if SP and the Power Generating Companies could hedge the future price correctly, they stand to earn a good profit.

As no contract or hedge will be able to cover all future price variations, at some point, consumers inevitably will have to pay for any higher fuel cost incurred by SP and Power Generating Companies. This is when EMA can come in to mitigate. Asking the consumers to pay electricity rate upfront based on a forward contract price is not necessary the way to protect the consumers’ interest.

Conclusion
EMA has chosen the forward fuel oil pricing to be "peg" to evaluate electricity rate but this pricing has lesser transparency. They also used forward fuel oil pricing quoted 3 months ago. There will always remain a question as to whether this forward fuel oil pricing is a good peg to protect the consumers' interest.

Afternote: EMA was referring to SWAP fuel oil pricing as Forward Fuel Oil pricing

Related Articles

1. Confusion in the use of Forward and Swap Fuel Oil Pricing
2. Is it fair to use Forward Fuel Oil Pricing?

Repairing Ultrasonic Humidifier

2 October 2008

Ultrasonic humidifiers have been used extensively in temperate as well as in tropical countries. They are used to keep room humidity at comfortable level. They are pretty cheap and simple to operate. They need little maintenance except for the frequent topping up of the water. This article will describe the workings of various electrical and electronic components and touch on how to repair some common faults.

What is Ultrasonic humidifier (UH) ?

Please refer to this article




What are the components inside the humidifier?

The humidifier consist of the following components
a) Control Panel (analogue or digital)
b) Mechanical fan
c) Water container and water level sensor
d) Electronic ultrasonic Generator
e) The piezo-electric transducer






How do these work?

a) Control Panel

Analogue or digital type. This panel will allow users to control the amount of mists generated and/or speed of the fan. Some humidifiers have built-in humidistat that will regulate the amount of mist to a preset control;



b) Mechanical fan

This is usually a small mechanical fan used to distribute the mists. It is made from using a small single-phase shaded pole a.c. motor with a centrifugal fan attached.
c) Water container and water level sensor (aka float switch)

The water container is usually an inverted container that can hold about 4 to 5 litres of water, enough for one day’s operation. The top end of the container is always sealed such that as water is being drawn from the container, it will create a vacuum on top of the container which will hold the water above the water level. All UH has a water level sensor or float switch that will stop the operation of the humidifier when the water level is low.



d) Electronic Ultrasonic Generator

This usually consists of a power switching transistor arranged as a Colpitts oscillator to provide power to the piezo-electric transducers. The oscillating frequencies are around 0.8 MHz to 1.7 MHz.




e) The Piezo-Electric Transducer
Connected to the output of the electronic ultrasonic generator is the peizo-electric transducer, which looks like a 50 cts coin or a lithium battery of that size.

During the humidification process, the peizo-electric transducer will vibrate at ultrasonic speed and water will be broken up into mists of 1 to 3 microns when they come into contact with the vibrating transducer.

What Can Go Wrong?

When the humidifier stop working, it could be due to many factors but this article will concentrate on one of the most common problem: the humidifier is working but it is just not strong enough to create the mist. Some water circulation is seen on top of the transducer.

There are a few reasons:
a) Clogged Transducer

This normally don’t happen if one uses soft water as recommended and cleans the transducer often. However, should a de-scaling required, do not use any chemical or soap or scrap the transducer surface with any hard objects. They might attack or damage the thin coatings of the transducer. A soft brush, brushing the surface may be sufficient. If this cannot remove the scaling, try some soft cleaners such as alcohol or other soft cleaners and rub against the surface of the transducer softly.
Handle the transducer with care. Transducers are made of ceramics. They are hard and very brittle. They will break into pieces once they fell onto the floor.
One can buy replacement ceramic disc from some aquarium shops that sell mist makers for fish tanks. They are packed together a key as shown and they are pretty cheap.

b) If the cleaning of the transducer does not work, it is likely that the oscillator may be at fault. It might be due to the following reasons:

1) Faulty Power Supply Unit

The power supply is from a 35-40 volts power transformer. This power is fed to a set of 4 diodes that form a rectifier bridge. The output of the bridge is filtered by a smoothing capacitor in the range of 2 to 50 uF (C5 or capacitor connected immediately after the bridge). If this smoothing capacitor is faulty, it will not deliver enough d.c. power to the oscillator circuit
2) Faulty Oscillator

The capacitors that form the oscillator could have been faulty and as a result, the oscillator is oscillating at other frequencies that could not deliver enough power to the transducer

3) Fault Power Switching Transistor

If this transistor is faulty, it is likely that oscillator will not work. Check the transistor for proper operation. Not every transistors are made the same for operation. Equivalent transistor may not work properly.


Schematic Circuit of other Brand
 Other reference circuitary on application of ultrasonic transducers can be found here.

Fuji Ceramics Corporation

Note: If you find schematic diagram of other brands, please email me.


4) Bad Contact at the Transducer

The transducer is usually connected to the circuit through a spring to allow the transducer free to vibrate. Bad electrical contact between the spring and the transducer may cause the unit to stop working. Dismantle the transducer and polish the contact surfaces at the transducer and the spring to ensure good electrical contact.

Related Articles
1. Soft Water Supply for Ultrasonic Humidifiers
2. Cut Electricity Bills by up to 90%