History of Electrical Engineering

Benjamin Franklin in 1752, was the first man who tried to utilize electricity from clouds by flying a kite during a stormy night. In 1780, Luigi Galvani was surprised when he saw that a dead frog’s leg twisted when it was touched by a silver and copper stick. He misunderstood the actual reason, thinking that the electricity came from the leg itself, and referred it as animal electricity. After development in 1800 by Alessandro Volta of the voltaic cell as a simple method of producing electricity from a chemical reaction, an actual revolution occurred in this field and the history of electrical engineering totally changed from this time.


It is needless to say that most of the theories, on which this field of engineering is built, are related to electromagnetism. The law of electromagnetism was invented by Michael Faraday in the year 1831. This law is popularly known as Faraday’s law of electromagnetic induction. The relation between current andvoltage in a conductor was already stated by Georg Ohm, in 1827. This is Ohm’s law . Based on these two theories development of electrical technology began. In his experiment with electromagnetic induction, Michael Faraday designed the most basic model of an electrical rotating machine. In 1873, James Clerk Maxwell, published his famous article on magnetism and electricity.

Werner von Siemens the founder of the German multinational engineering and electronic company Siemens, made great contributions in the early days of the history of electrical engineering. He was a great inventor and developer. Another great contributor to the electrical engineering was Sir Thomas Edison. We all know him as inventor of electric light bulb in the year 1879. This invention was a revolution. He was also the builder of the first electrical supply network in the world.


Although there were so many developments and research works going on before 1882, the study of electricity was not recognized as a separate field of engineering. In that year electrical engineering was introduced as a separate branch of engineering by TU Darmstadt University Germany. This was the beginning of studying electrical engineering as a professional degree. In that very year Edison started the world’s first electric supply business at DC 110V. Initially, a total of 59 houses in Manhattan were connected to his network.

Although, alternating current had already been developed in Europe in the year 1850 by Guillaume Duchenne, it was not yet commercially distributed. George Westinghouse, an American entrepreneur and engineer, finally came forward and financially supported the development of the AC power network. By the end of nineteenth century AC power transmission and distribution became popular and started dominating DC distribution systems.


After development of the distribution network, electricity reached consumers. After electricity reaches the consumer, it is utilized for operating different equipment run by electricity. Electrical engineering is also involved in developing such industrial and domestic equipment at the consumer end. Many scientists and engineers involved themselves in inventing and developing such equipment. A new window had been opened in history of electrical engineering.

In 1895, Nikola Tesla transmitted radio frequency signal across a distance of eighty kilometers and developed radio transmitters.
In 1897, the cathode ray tube was invented by Karl Ferdinand Braun and development of television technology began.
In 1902, Willis Carrier developed air conditioning machines.


In 1941, Konrad Zuse introduced the first form of programmable electromechanical computer.
In 1943, Tommy Flowers produced first prototype of programmable digital computer.
In 1946 Percy Spencer invented the microwave oven.
Every day there are new inventions and developments in electrical engineering and technology. The discussion is far from over. Here, we tried to give an overview only.

Creat Digital Voltmeter Circuit using ICL7107

Digital voltmeters are often preferred these days over analog voltmeters owing to their accuracy and high rate of precision. Also digital systems are preferred because of their less exposure to noise and good data compression capability. A voltmeter is an instrument measuring the potential difference between two points. A typical digital voltmeter consists of a analog to digital converter and a digital display.

Analog to digital conversion involves transforming a signal from its continuous form to discrete form using electronic integrated circuitry. An analog to digital converter can be a dual slope converter, successive 

approximation converter, flash converter or a delta sigma converter.

 Here we design a analog to digital converter working as a digital voltmeter using a low power three and half digit A/D converter ICL7107 having internal 7 segment decoders, display drivers, a reference and a clock. An advantage is this IC can directly drive non multiplexed seven segment display without any external decoding circuitry. The circuit can measure voltage in the range of 200mV to 2V with an interval of 0.001V.

Principle Behind the Circuit:

This circuit is based on the principle of using ICL7107 as an analog to digital converter. The whole operation is divided into two phases- Analog to digital conversion and decoding. Analog to digital conversion is done using the process of integrating and reference integrating. In other words, the input signal is first integrated to bring the output of integrator to ramp signal and an opposite polarity reference voltage is then integrated to bring the output of integrator back to zero. The resultant digital code obtained is then decoded using to display decoders to drive the display unit.

Do you know the working of Digital Voltmeter Circuit using 8051 Microcontroller?

Digital Voltmeter Circuit Diagram using ICL7107:

Circuit Diagram of Digital Voltmeter using ICL7107

How Design Digital Voltmeter Circuit?

Designing the circuit requires appropriate selection of the components as given below:

1. Selection of Oscillation Circuit Components:  For a typical oscillating frequency of 48 KHz, the oscillating resistor has been chosen to be about 100K and the capacitor about 100pF.
2. Reference Capacitor: The value of reference capacitor is chosen to be between 0.1uF and 1uF. Here we choose a 0.5uF electrolyte capacitor.
3. Auto-zero Capacitor: The auto zero capacitor is selected such that its value is between 0.01uF and 1uF. Here we select a 0.1uF capacitor.
4. Integrating Capacitor: The integrating capacitor forms an essential part of the integrating circuit. Its value is determined by the integration period t, optimum integration current I and integrated voltage Vint. For a time period of 83mSec, current of 4uA and voltage of 2V, the value of capacitor is found to be around 0.16uF. Here select a 0.22uF capacitor.
5. Integrating Resistor: The value of this resistor is given by the full scale analog input voltage and the optimum integration current. We select a resistor of 500K for a full scale input voltage of 2V.

How to Operate Digital Voltmeter Circuit?

The IC is powered by a dual supply of +/- 5V. Once the circuit is powered, the reference signal is set by adjusting the reference resistor. The reference voltage needs to be about half of the input voltage. The oscillating components – resistor and capacitor determine the oscillating or clock frequency of the device. The reference capacitor is charged to the reference voltage. A feedback loop is then closed to charge the auto zero capacitor such that is compensates for any fluctuations in voltages. Later the converter integrates the differential voltage at the input for a fixed time such that output of the integrator is a ramp signal. A known reference voltage is then applied to the input of integrator and is allowed to ramp till the output of integrator becomes zero. The time taken for the output to return back to zero is proportional to the input signal and the digital reading is given as:

Display Count = (Vin/Vref)*1000.

The next process involves decoding the digital count to produce a seven segment compatible signal so as to drive the displays. The digital output is then displayed on the multiplexed 7-segment display.

Applications of Digital Voltmeter Circuit:

1. This circuit can be used in digital multimeters to provide digital reading of measured voltage.
2. It can be used to measure AC and DC voltages.
3. It can be used to measure physical quantities like pressure, temperature, stress using transducer circuit and signal conditioning circuit.
4. It can be used in applications where high accuracy and high resolution is required.

Limitations of Digital Voltmeter Circuit:

1. It can measure voltages only up to a low range.
2. The IC used is a CMOS device and is highly static.
3. Difference in reference voltage for negative and positive input voltage can cause rollover error, i.e. a common mode error.
4. Using a full scale negative input voltage of 2V can sometimes cause output of the integrator to saturate.
5. Internal heating from the LED drivers can cause degradation in performance.
6. Reference temperature coefficient, internal chip dissipation and package thermal resistance tend to increase the noise level.