A Real Example of Continuing Professional Development

Continuing professional development for STEM related subjects is important for individuals, companies and the economy.

This article covers the major CPD steps of the author and is illustrated with a sequence of simple cartoons.

Dates are very approximate and the cartoons and associated content are personal landmarks, but they also represent major technological developments.

Some educational consequences of profound and rapid technological change are summarised at the end of the article.

Figure 1 Vacuum Tubes- before and up to 1960

Figure 1 Vacuum Tubes- before and up to 1960

A Pentode vacuum tube (valve in the UK) and a coffee cup.

The pentode has 5 elements, anode, cathode, control grid, screen grid, suppressor grid (5 pins)

It also has a heater which has 2 pins.

The pentode is used to amplify small signal voltages.

Typically the small electrical voltages used in a radio could be amplified using a pentode.

The amplified signal voltage are then applied to a speaker to produce sounds, such as music or voice.

Table 1 -Typical Pentode Details - pen means 5, 5 active pins
Element Name Voltage Current Comments
Anode 200V d.c. 3.0mA d.c. Voltages and currents are typical
Cathode 0V 3.5mA d.c. Current = Anode Current+ Screen Current
Control Grid -2V 0  
Screen Grid 140V 0.5mA d.c.  
Suppressor Grid 0V 0  
Heater 6.3V a.c. rms 200mA a.c. rms Requires 2 pins




Data based on EF86 supplied by Mullard.

Typical power consumed by a single pentode is about 1.9 Watts

Vacuum tube types: diode , triode , tetrode , pentode.

Each tube type has a heater, which boils off electrons from the cathode.

Figure 2 Vacuum Tube Radio, before and up to 1960

Figure 2 Vacuum Tube Radio, before and up to 1960

One of the main economic drivers for electronics was radio. The other was the 2nd world war.

Originally radios used vacuum tubes, a typical radio would use 5 or 6 tubes.

The valves used to drive the speaker were power devices, they were large, heavy and power hungry.

In addition, these radios used a large, heavy transformer to convert a.c. power to d.c. power.

Consequently, valve radios were large, heavy, and consumed a lot of power- ten's of watts.

Figure 3 Vacuum Tube Television: 1936- 1939, 1946-1960

Figure 3 Vacuum Tube Television: 1936- 1939, 1946-1960

Television was broadcast in UK from 1936 to 1939, but discontinued when the 2nd world war broke out.

In 1946, after the war, broadcasts were resumed.

The war prevented development of commercial TV but it drove the development military electronics like radar.

A key invention was the cathode ray tube (CRT), used to display TV images.

The CRT is a specialised vacuum tube that uses supply voltages of about 20,000 Volts.

Modern silicon integrated circuits use supply voltages of 3V.

By the 1960s billions of TV's used CRT's and CRT's were used in many other applications.

A TV set was large, heavy and consumed a lot of power.


Figure 4 A Transistor Radio: 1956 to Present

Figure 4 A Transistor Radio: 1956 to Present

The first transistor radio was introduced in the UK in 1956.

By the 1960's the transistor radio was used extensively, world wide.

The transistor is a solid state device, it is small, reliable, works off low voltages, e.g. 12 volts and has low power consumption.

Item (a) depicts an early transistor radio, (b) is a small signal transistor and (c) is a power transistor.

The transistor heralded portable electronic devices.

Transistors are triodes, they have 3 active elements, a collector (anode), emitter (cathode) and a base (control grid).

A transistor radio used about 6 transistors.

Figure 5 Integrated Circuits- about 1965

Figure 5 Integrated Circuits- about 1965

The increasing complexity of electronic devices spawned the development of integrated circuits.

The earliest integrated circuits were made up of a group of transistors mounted on a substrate- they were connected to perform special functions.

The 7400 device (a) is a quad 2 input Nand gate: NAND gates are Logic devices used extensively in digital computers.

About 16 transistors are used on the 7400 device- this is a small scale integrated circuit (SSI).

Item (b) is an example of a large scale integrated circuit (LSI), it is a microprocessor, that is a small computer.

Integrated circuits are small, reliable, work off low supply voltages and have low power consumption.

Microprocessors heralded the use of software on a grand, universal scale- the early languages used assembler techniques.


Figure 6 An Early Personal Computer (PC)- about 1975

Figure 6 An Early Personal Computer (PC)- about 1975

Early personal computers were effectively hybrid systems, they used solid state integrated circuits to process data and a CRT display.

It is easy to identify old computers, just look at the back of the display- if it sticks out a long way its a CRT display.

The display voltage is about 20,000 volts.

In comparison with main frame computers, PC's are small, use little power and are not heavy.

In comparison with a transistor radio, they are large, heavy and consume a lot of power.

Early PC's were not portable.

The advent of the PC made computers available to ordinary people.

To make PC's portable, a replacement for the CRT was required, LCD and LED flat displays.

Figure 7 Primitive Software Development System- about 1980

Figure 7 Primitive Software Development System- about 1980

The combination of integrated circuits, microprocessor and assembler languages impacted the development of electronic products significantly. The first software development systems were very primitive- code was entered into the products memory using a hexadecimal terminal which was about the size of a calculator.

The program consisted of a long string of hexadecimal characters, such as F8, AB, F9, C8 etc. A sequence of characters represented an element that could be interpreted by the microprocessor. If a mistake was made the string had to be modified- inserts, copy, replace etc were not possible.

Surprisingly quite large programs could be developed consisting of 1000's characters, using this approach.

Assembly languages were quickly developed, which had character strings that were meaningful to humans and could be interpreted by computer. For example, LDI B6 could mean load a register with the hex number B6.

Very quickly, the whole process was computerised: code was written using text editors, compiled by computer and debugged on computer.


Figure8 An ASIC Consumer Product- about 2000

Figure8 An ASIC Consumer Product- about 2000

The revolution in the reduction electronic product size gathered momentum, the size of transistors were being reduced, product development tools allowed computerised design of complex systems and manufacturing techniques became increasingly refined.

The product shown is an example of an Application Specific Integrated Circuit (ASIC).

This is a customised integrated circuit designed for a specific use- the size of the integrated circuit is about 10 mm2: it holds thousands of transistors.

The product runs off a standard coin type battery and its operating current is less that 500nA (500 billionths of an amp).

Power consumption was about 1.5 µW, 1.5 millionths of a watt.

Product sales are in the millions each year, at a price of about $2 (USD) per device.

At the time of writing, integrated circuits and ASIC's are being produced using millions of transistors per mm2.

Figure 9 Online Education: 2014

Figure 9 Online Education: 2014

Portable electronic products abound, they are sophisticated and often aesthetically pleasing.


The Internet and mobile phone networks make instant communication across vast distances possible.


Display technology has become almost ergonomically perfect- their thickness is approaching that of a sheet of paper.


TV, radio, mobile phone and computer technologies are merging.


It is as though the human race is developing a nervous system, utilising distributed intelligence.


This poses vital and important questions for educationalists:

How de we teach these rapidly changing technologies ?

How do we use these rapidly changing technologies in our teaching ?

How do we keep up to date?

Summary of the Effect of Technological Change on CPD for the Engineer

CPD extends over the working life of the engineer

An engineer spends more time on CPD than formal education

Technological change dictates when CPD is required.

CPD should be available when engineers need it- they can't wait for several months for a course to become available.

CPD should provide tangible, measurable benefits for employers and employees.

It should be affordable to employees and employers.