November 22, 2006

California RoHS law

OK, so you might think you are not selling your products in Europe and you don't have to worry about RoHS. Nah!
Beginning in January 1, 2007, a California law will ban the sale of some electronic devices if they are prohibited from sale in the EU because they contain certain toxic metals.
At present CA’s RoHS law will be similar to EU RoHS Directive, but narrower in the scope of affected products and the number of restricted metals.
Here are some highlights of the CA's RoHS law:
  • It applies only to so called “covered electronic devices,” which are defined as video displays with >4" screen (such as CRTs, CRT and LCD TVs, computer monitors, laptop displays, plasma televisions).
  • It does recognize all exemptions adopted by the EU.
  • It restricts only four out of six substances (Lead, Mercury, Cadmium, and Hexavalent chromium) and does not restrict the use of PBBs and PBDEs. However, the use of flame retardants such as PBDEs is already banned under California Health and Safety Code since June 1, 2006.

Complete info is available at California Department of Toxic Substances Control. Also, you may want to get RoHS, WEEE and China RoHS manual as well as China RoHS EFUP guidelines translation.

August 6, 2006

Enhanced web searches for generators and power supplies

No matter how good Google search algorithm is, a purely mechanical algorithm can't always determine which sites are really useful and which are not. In addition, no search algorithm can know exactly what kind of info you are looking for. We all know that general purpose search engines bring up a lot of junk.
To address these issues Google recently launched Custom Search Engine (CSE) program which enables you to enhance your search by using human expertise and by specifying what type of info you are looking for. Particularly, my content is intented to improve your search experience in topics related to electrical generators and power electronics/SMPS.

EXAMPLES. Say, you want to choose a home generator and looking for something to start with. If you select my Guides/Reviews category, on the first search results page among other buyer's guides you will find a link to a very handy Consumer Reports' rating of generators. Otherwise, with a regular Google search this link is not among the top search results.

Alternatively, if you are looking for physical principles of electric generators you may want to eliminate commercial and advertising sites which represent more then half of the top results in "electric generator" query. Even if you try a more specific query like "how electric generator works", many relevant pages are still not at the top. Why? Because a search engine goes mainly by keywords you entered- obviously it does not know how generators work. Many web pages that describe in depth generator theory just do not use all these terms and won't show up in your top results. They do use more important terms though- you can't really describe generator's operation without using such words as Faraday, induction or magnet. That's why these terms are added to my "Generators/Physical principles" label. If you select this label, they will be automatically added in background to your query as additional search terms. This will make your refined search results more relevant and will weed out unrelated pages. In addition to this, web pages that I've personally reviewed and found useful for this topic will increase in importance within your refined search results and will be marked accordingly while spam sites and sites with unrelated or useless content will be pushed down in your custom search results.

You can do your search from my respective search engine page or

I encourage you to give it a try and see the difference for yourself. Note, this is a work in progress. I keep testing different keywords and algorithms to provide you with the most relevant search results. All comments are welcomed. To subscribe [by using any email address] click on this button:
Last revised on 2013.

July 23, 2006

Internet plagiarism

If you publish a website you may want to know if someone copied its content without your permission and is taking your work as their own. There is a nice free online tool that can help you combat Internet plagiarism: You can enter your URL in their search box and they'll list sites that have sentences and phrases identical to yours. You'll even see the duplicated text highlighted.

When I run their search for my site among the results was a British company named Powerstax. Their Power Glossary page contained a number of definitions (such as Isolating power supply, Linear power supply, Off-line power supply, SMPS) from my copyrighted page

I sent a complaint to their webmaster and to other individuals whose email addresses were listed, but no one responded.

Note that definition of power electronics term on my page generally differ from those you may find elsewhere. I put up this web page because I felt the definitions given in textbooks and other sites are often inaccurate or even misleading. For example, the term Isolation is often defined as absence of current path between two circuits. In reality, it is only absence of DC current pass- as we know many isolated circuits still allow some capacitive AC current.

I was curious if the rest of the terms on Powerstax glossary page are unique. So, I run Copyscape search for their page. Guess what- the search returned glossaries of several other power supply sites. Of course, when it comes to these sites I can't know for sure who copied whom. I do know this when it comes to my site though.

July 6, 2006

RoHS overview

This year and the coming years will be challenging for electronic industry. As the July 1 RoHS deadline has come into force, no new equipment sold in EU may contain certain levels of six toxic metals: lead (Pb), mercury (Hg), hexavalent chromium (Cr (VI)), cadmium (Cd), polybrominated biphenyls (PBBs), and polybrominated diphenyl ethers (PBDEs).

Of course it is a noble idea to make electronics environmental friendlier and its recycling easier and safer. However in reality it will take years until we see all consequences of implementation of RoHS (The Restriction of Hazardous Substances) Directive. It is worth noting that the EPA report on Solders in Electronics: A Life-Cycle Assessment (August 2005) suggests that the lead-free solder replacements will have a higher environmental impact than tin lead solder in a number of areas including global warming, ozone depletion and water quality.

I also wonder what will happen with all existing non-RoHS part inventory. I guess some of them will wind up in the landfill. Others (as my boss suggested) may return to the open market through third world countries as counterfeit RoHS-compliant parts. Indeed, many manufacturers do not change part numbers and marking when they make the transition to RoHS products. For such parts, the only way to determine whether it is really RoHS-compliant is to compare its date code to the manufacturer's conversion date- something you can't do for small package sizes with no date code marking on the part itself.

The biggest challenge of course is switching to lead free solder. The main issues with lead-free allows are:

  • Tin-lead alloy has melting point of 361 F (183 C). The typical alternative alloys have melting point higher by at least 63 F (17 C). The higher temperature could damage PCBs and other components, which requires changing in the manufacturing process and materials.
  • In alternative alloys, liquid solder may not attach itself to a surface as good as tin lead allow (poor "wetting")
  • Possibility of "tin whiskers" (effect of growing tiny metal "hairs")
  • Nobody but nobody knows long-term reliability effect of new solder

Fortunately, RoHS directive has exceptions for a number of critical categories that cannot afford any risk, such as aviation and military equipment, most medical devices, and large-scale industrial tools. Server, network and telecommunication infrastructure equipment can continue using lead in solder until 2010 and still be RoHS-compliant (so called RoHS-5 or "lead exempt"). The rest of equipment, particularly general purpose power supplies with a voltage rating below 1000 VAC / 1500 VDC not falling into the above categories has to comply.

So, what does all this mean for the electronic industry?
I guess until the dust settles we may frequently see: delayed shipments as manufacturers struggle to weed out non-compliant parts and change manufacturing process, worse financial reports, unpredictable quality issues especially with manufacturers who do not have advanced product screening system (such as HASS) in place.

Well, whatever it takes to satisfy European lawmakers (-:

June 11, 2006

How to Avoid Postage Rate Increases

This year US Postal Service has increased postal rates by approximately 5%. I understand they are also seeking another increase of approximately 8% in the spring of 2007. Despite this, the Postal Service is expected to finish this fiscal year about $2 billion in the red. Is this not a good example of what happens when you let government bureaucracy handle a business? In reality, there is no reason why the postage can't be much cheaper or even be free. How? Very simple- just like public television, radio, email, etc. can stay free.
Just let private companies sponsor the cost of the postage. Let the stamps feature IBM, Dell, APC, etc. rather then flowers. Or let advertisers print postage-paid envelopes with their ads. Of course, the stamp collectors should always be able to buy stamps just like those who are not satisfied with free email can buy a premium one. Just give us the option of low-cost or free ad-sponsored postage. (Ok, this is not exactly about power electronics, except when you need to mail your resume the old fashioned way (-: ).

April 22, 2006

Power electronics resources

Hi, there. To divert a portion of the traffic from my main website I've opened a supplementary site with Power supply/ Power electronics calculators, news and career resources: .
Although it is still under development, feel free to stop by and check it out.

March 25, 2006

Engineering Jobs Page

Engineering Jobs page on my website is now up and running (you may click on the title of this post to go there).

It provides convenient (I hope) tools for both job seekers and employers. There are also separate pages for power supply design jobs and pcb design jobs.
Bye for now.

February 21, 2006

Hello, SMPS enthusiasts

I decided to supplement my Power Electronics/SMPS corner with this blog.
I am going to post here updates about my website and some related thoughts. At this point I am not sure I will have time to maintain it though.
If there is anything you would like to see here- please comment.
Bye for now.