Wednesday, May 30, 2012

Happy Harvest Festival

To all KDM friends, Happy Harvest Festival!

Friday, December 25, 2009

Merry X'mas !

Wishing all my Christian friends a Merry Christmas!

Thursday, August 07, 2008

Starting over

I switched from Blogger to Blogcharm when they promised to pay bloggers for blogging on their site.
Alas,they discontinued the service soon afterwards,and I did not have backup for the posts on Blogcharm! Now I have no choice but to return here and start all over again.

Monday, January 02, 2006

Basic principles

Electric charges are divided into positive charge-proton and negative charge-electron.
The electrons are constantly attarcted to the protons within its vicinity to form an atom.This force of pulling them togehther is the electric force.Hence the science of electronics is the study of the behavior of electrons under set conditions.
When two poles (eletrodes) with different voltages one positive,the other negative are placed close to each other,free electrons from the negative electrode will follow towards the positive electrode.The phenomenon just described is not possible in open air,but it will be possible within a vacuum glass tube where the electrons can follow unobstructed.
Here the positive eletrode is given the name Anode (or plate as sometimes called),the negative electrode is called the Cathode.
The diagram on the right shows more than 2 legs,what are the extra legs? They are the heaters' supply leads. The number of free electrons emitted from the cathode will increase many folds when it is heated.More electrons,more electric current,so heaters are introduced.
We have just learned the principle behind the operations of the most basic vacuum tube the Diode.
Diodes were used principally in rectifiers of alternative current into direct current.
We will next describe a far more important device the Triode in another post.

Sunday, January 01, 2006


Vacuum tubes,thermionic valves,made it possible for technicians and circuit designers to manipulate the feeble electric signals decades ago.The first vacuum tubes were thermionic diodes which were used exclusively as rectifiers.This type of electronic device had only two eletrodes-the anode and the cathode.With the introduction of a third electrode,the gird,as a controlling device the triode vacuum tube was born.Tetrodes and pentodes were also built later on.
Wih this discovery,the world of electronics is suddenly here.It changed the way we do things,in fact our life is no longer the same any more!
Today,the vacuum tubes is just a thing in the memories of us old timers,many of the young engineers of today may have never hard of them before.Yet vacuum tubes are still in use in large broadcasting transmitters and in the homes of the audio hifi fanatics.The output of the vacuum tubes audio equiment have much higher fidelity than their solid state counter parts.Hence they remain the favorites of the hifi enthusiasts.
I will share with vacuum tubes(valves) lovers what little I know on this subject in this blog.