Home  Vacuum Tube

Oct 31 2019

Vacuum Tube Computer Definition and Basic Idea

Ⅰ Introduction

The main feature of the vacuum tube computer is the use of the electron tube as the basic electronic component, which is large in size, large in power consumption, short in life, low in reliability and high in cost, and the internal memory uses a mercury delay line. During this period, there was no system software, programmed in machine language and assembly language. Computers can only be used in a few cutting-edge areas, generally for scientific, military, and financial calculations.

Although the first generation of electronic computers are quite clumsy, bulky, expensive, and difficult to operate, it is the road to computer development that has revolutionized human social life. The first generation of electronic computers refers to the time from 1946 to 1958. At this time, the basic circuit of the computer is the use of the electron tube structure, and the program transitions from the manual hand-programming machine instruction program to the symbol language. The first generation of electronic computers is the beginning of the revolutionary development of computing tools, and its binary system and program storage have laid the foundation for modern electronic computer technology.

On February 14, 1946, the first electronic computer named ENIAC was born at the University of Pennsylvania. However, it is bulky and extrapolated from the program, which is not convenient to use. Computer operations taking a few minutes or hours requires hours to days to program. When ENIAC's development was nearing success, John von Neumann, who served as a consultant at the Bertin test site, knew the news. After carefully studying the advantages and disadvantages of ENIAC, he gave a new EDVAC design in 1946 with the assistance of others. The computer in this scheme includes calculator, controller, memory, input and output device. In addition, binary is used in electronic computing for the first time and program memory is implemented to increase the speed of computing, which makes automatic operations possible.

So far, it is the foundation of all computer design. In 1949, the University of Cambridge was the first to make the world's first program memory computer EDSAC with electronic delay storage. Von Neumanns EDVAC was made in a few twists and turns, and was finally made in 1952. In addition, Chinese-American An Wang proposed the idea of storing data with magnetic cores in 1950, and the magnetic core memory was patented by him in 1951. It is used as the main memory of almost all electronic computers in the 1950s to 1970s.

Ⅱ The Seeds of Computers 

In 1904, the world's first electron tube was born under the British physicist Fleming. Fleming obtained the patent for this invention for this purpose. The birth of the first human tube, marking the world has entered the electronic age. The world's first computer uses 18,000 tubes, covering an area of 170m*2, weighing 30t and consuming 150kW.

Talking about the invention of the electron tube, we must start from the Edison effect. When studied the life of an incandescent lamp, he welded a small piece of metal around the carbon filament of a bulb. As a result, he discovered a strange phenomenon: although the metal piece is not in contact with the filament, the filament will generate a current that tends to the nearby metal piece when a voltage is applied between them. Where did this mysterious current come from? Edison couldnt explain it, but he registered the invention with a patent and calling it the Edison effect. Later, it was proved that the current was generated because the hot metal could emit electrons to the surroundings. But the first to anticipate the practical value of this effect is the British physicist and electrical engineer Fleming.

Fleming's diode is a brand new invention, and it works well in the lab. However, for some reason, it is not very successful in the actual use of the detector, because it is not as reliable as the natural detector that was invented at the same time. Therefore, there was no impact on the development of radio at the time.

Shortly thereafter, the inventor of the American inventor De Forrest, ingeniously added a grid between the filament and the plate of the diode, invented the first vacuum transistor. This small change has brought unexpected results. It not only responded more sensitively, but also emits vibrations of music or sound. Moreover, it combined the functions of detection, amplification and oscillation. Therefore, many people regarded the invention of triodes as the real birth point of the electronics industry. De Forrest himself was also very surprised, saying that I found an invisible air empire".

vacuum tubes

The advent of electronic tubes has promoted the booming of radio electronics. By around 1960, the radio industry in the western wold had an annual production of 1 billion radio tubes. In addition to telephony amplifiers, marine and air communications, electronic tubes are also widely used in home entertainment, broadcasting news, educational programs, literature and music to thousands of households. Electron tubes also supported the invention and further development of aircraft, radar, and rockets.

The three - legged magician tube was a handy tool in electronics research. The tube device has been dominant in the field of electronic technology for more than 40 years. However, it was undeniable that the electron tube was very cumbersome, had large energy consumption, short life, and high noise, in addition, the manufacturing process was also very complicated. Therefore, soon after the advent of the electron tube, people were trying to find new electronic devices. In the Second World War, the shortcomings of the electron tube were more obvious. The ordinary electron tube used in the radar working frequency band is extremely unstable, and the tubes used in mobile military devices and equipment were more awkward and prone to failure. Therefore, the inherent weakness of the tube and the urgent need for wartime had prompted many scientific research units and scientists to concentrate on rapidly developing new solid components to replace electron tubes. Later, the tube was replaced, and the alternative to the tube was called a transistor.

 6550 EH vacuum tube

Ⅲ Basic Parameters of Vacuum Tubes

1) filament voltage

2) filament current

3) anode voltage

4) anode current

5) grid voltage

6) grid current

7) cathode input resistance

8) output power

9) transconductance

10) internal resistance

a. Amplification factor μ= Uak/Ugk  anode voltage: Uak; gate voltage: Ugk )

It represents the ratio of anode voltage to grid voltage while keeping the anode current constant.

b. Transconductance S=Ia/Ugk ( anode current: Ia; gate voltage: Ugk )

It is shown that in the case where the anode voltage is maintained constant, a unit gate voltage changing will cause how many units of the anode current be affected. 

c. Internal resistance Ri=Uak/Ia ( gate voltage: Uak; anode current: Ia )

It is shown that in the case where the gate voltage is maintained constant, a unit gate current changing will cause how many units of the anode voltage be affected.

The above values can also be expressed as magnifying factor μ = S × Ri

 

Ⅳ History of First Generation Computer

vacuum tube computer

ENIAC (Electronic Numerical Integrator and Calculator), the world's first electronic computer is a giant: weighing 30 tons, covering an area of 170 square meters, with 18,800 internal tubes, 6000 switches, 7000 resistors, 10,000 capacitors, 500,000 wires, and consumes 140 kilowatts power, 5000 additions/second can be performed. In the Second World War, both sides of the enemy used aircraft and artillery to violently bomb the other military targets. To be accurate, it required  accurately calculate and drawn a shooting chart. After checking the table to determine the angle of the muzzle, the projectile can be shot in the middle of the target. However, each number can be obtained by a thousand operations of several thousand times. A dozen people can count a few months with a mechanical computer to complete a chart. In response to this situation, people began to study the use of electronic tubes as "electronic switches" to improve the computing speed of computers. Many scientists have participated in experiments and research, and finally made the worlds first electronic computer ENIAC.

In the mid-1940s, the Department of Electrical Engineering at the University of Pennsylvania, led by John W Mauchly and J Presper Eckert, developed an electronic numerical integral computer ENIAC for the calculation of ballistic trajectory of artillery for the Aberdeen Ballistic Research Laboratory of the US Army Ordnance Department. This behemoth was unveiled in the United States on February 15, 1946. The advent of this computer marks the beginning of the computer age.

The earliest computer before the predecessor was a kind of adder. It was invented by a French mathematician Baskar and later improved, and it can be used as a differential machine for four arithmetic operations.

In 1801, the Frenchman Joseph Jacquard invented the Punchedcarboardcard. This introduces two important concepts for the development of future computers:

First, the information can be encoded on the punched card (coded), which is the program. Second, the information can be stored on the card, and when the cards are grouped together, they can be used as a series of instructions, that is, programs. Then there was a person, Charles Babbage, called the father of the computer, he made a more powerful machine analytical engine, which was very similar to modern computers.

These inventions are tools used to aid computing, and there is no function to memorize and store data, so it cannot be called a computer (if the function of the computer is strictly defined), until 1946, The United States' Mokley and Eckert invented the first generation of computers, ENIAC, and the first generation of computers covered an area of two classrooms. The computer parts at that time were vacuum tubes, and the storage was the punchedcarboardcard.

Therefore, the invention of the computer is the result of the joint efforts of a group of researchers, but the design idea of the mathematician von Neumann played a key role in it, so he was called the father of modern computer.

The first generation of computers is characterized by operational commands that are programmed for specific tasks. Each machine has its own different machine language, with limited functionality and slow operation speed. Another significant feature is the use of vacuum tubes and drums to store data. The first electronic tube computer (ENIAC) has 18,000 tubes to calculate in decimal up to 5000 times per second. Because of the limitation of time and technique, it has many shortcomings of large volume, high power consumption, high heat generation, short life, low power utilization, fragile structure and the need for high voltage power supply, etc. Except that, the loss rate of the vacuum tube is quite high, because it is possible to burn a vacuum tube almost every 15 minutes, and it takes more than 15 minutes for the operator to find the broken tube.

During this period, there was no system software, programmed in machine language and assembly language, therefore, it can only be used in a few cutting-edge areas, generally used in scientific, military, and financial calculations. With the time went by, most of them have been largely replaced by solid device transistors. However, the tube has a strong load capacity and a linear performance superior to that of a transistor. Its operating characteristics in the high-frequency and high-power fields are better than those of a transistor, so it continues to play an irreplaceable role in some places, such as high-power radio transmitting equipment.

As the first generation computer, it is a type of computer that is connected to the next generation, and promotes the development of computers.

0 comment

Leave a Reply

Your email address will not be published.

 
 
   
Rating: