We put a diode across a relay coil to protect other electronic components in a circuit from voltage spikes or “back EMF” (electromotive force) that can be generated when the relay coil is switched off.
When a relay coil is energized, it creates a magnetic field that causes the relay contacts to close. When the coil is switched off, the magnetic field collapses, and a voltage spike is generated across the coil due to the stored energy. This voltage spike can cause damage to other components in the circuit, such as transistors or microcontrollers.
Also Read – Why are colored balls used in Power Transmission Lines?
Why RCCB is a must? Why is RCCB necessary? What is RCCB? How does RCCB work?
By connecting a diode in parallel with the relay coil, the diode can provide a low-impedance path for this voltage spike to dissipate safely. This is because the diode is reverse-biased when the relay coil is energized, so it does not affect the normal operation of the circuit. However, when the relay coil is switched off, the diode becomes forward-biased, and it conducts the voltage spike away from the rest of the circuit, preventing any damage.
This diode is also known as a “flyback diode,” “snubber diode,” or “freewheeling diode.” It is a simple and effective way to protect sensitive electronic components from damage due to voltage spikes generated by inductive loads, such as relay coils or motors.
Diode – Types And Uses Of Diode
In this article on Diode, the information related to diode has been described in detail. What is a diode? How does it work? How many types of diodes are there? Where are diodes used? Hope this will be helpful for you.
What is Diode?
A diode is an electronics component made up of a P-type and an N-type semiconductor. Which is used in electronic equipment and circuits.
In the picture below, we can see that the diode has two terminals. The middle part remains slightly raised. There is a wire at both ends which is called a terminal. Most of the diodes are made from silicon, but apart from this semiconductor materials like gallium arsenide and germanium are also used.
The role of different types of small-looking diodes is huge in the world of electronics.
A diode has two terminals. One of its terminals is called the anode and the other is called the cathode. Now the question is, which is called an anode and which is called a cathode?
Any circuit is complete with positive and negative. The diode also has one side positive and one side negative.
In a diode, the positive terminal is called the Anode and the negative terminal is called the Cathode.
One side of the diode has a silver color coding. This coding tells us that this side is the cathode key, that is, the negative terminal key. Its opposite side is the anode that is the positive terminal.
Diode Symbol
The picture given below is of the symbol of the diode.
A triangle arrow with a single line next to it. The way the arrow moves, that kind of part is of the cathode ie negative. And its opposite side is the anode ie positive terminal.
What is the function of the diode? Diode Uses
The working of the diode can be understood very easily. The diode allows electric current to pass in only one direction, or allow it to be spread.
We saw above that a diode has two terminals, an anode, and a cathode.
The direction of current flow in a diode is always from anode to cathode. That is, the diode allows current to flow from the anode to the cathode.
Rectifiers are used to convert AC – Alternating Current into DC- Direct Current. In any electronic circuit, if the current is to be passed in one direction or to prevent the flow of current, diodes are used in all such circuits.
A diode is most commonly used to convert from AC to DC. It requires rectification. In which Half Wave Rectifier, Full Wave Rectifier, Bridge Rectifier are composed. A diode is used in this rectifier.
To control the current in the circuit.
To control the voltage in the circuit.
Used for circuit protection.
To convert light into electricity.
Used for signal.
Used to measure temperature.
Used in radio frequency.
How does a Diode work?
Diode works in two ways. A Forward Biased and Reverse Biased.
Forward Biased of Diode
Well, this is the main function of the diode. Allowing the electric current to pass through in forward biased only, the electric current flows through the diode.
For this, we have to make a connection on the terminal mentioned above. The anode of the diode is connected to the positive and the cathode to the negative terminal. Such a connection will allow the diode to pass current according to its capacity. This is called Forward Biased.
Reverse Biased of Diode
This process is opposite from forward biased. Where we used a diode to propagate the flow of current in one direction, here we use a diode to stop the flow of that current.
There is also a need to stop the flow of current somewhere in the circuit of electronic equipment. In such a situation, we have to use the reverse biased process only.
To reverse biased, or to stop the flow of current, we have to change the connection of anode and cathode.
In Reverse Biasing, the anode is connected to the negative and the cathode to the positive. Which stops the flow of current.
Remember – The connection of diodes is done in such a way that if the current flows, it is called Forward Biased and the current does not spread or stops flowing, such a situation is called Reverse Biased.
Types Of Diode
The invention of the diode is amazing in the electronic world. The role of a diode is very important for making electronic circuits work. As technology is increasing, we design diodes according to our needs.
Well, there are many types of diodes in the market. Diodes have to be installed according to the requirement of the circuit. The types of diodes are given below and they have also been described in detail.
Remember- Most of the diode names are based on the type of diode in use and some are known as inventors.
List of Diodes
1) Small Signal Diode
2) Large Signal Diode
3) Zener Diode
4) Light Emitting Diode – LED
5) Constant Current Diode
6) Schottky Diode
7) Shockley Diode
8) Peltier Diode
9) Crystal Diode
10) Silicone Control Rectifier – SCR
11) Step Recovery Diode
12) Tunnel Diode
13) Varactor Diode
14) Laser Diode
15) Photo Diode
16) Transient Voltage Suppression
17) Gold Doped Diode
18) Super Barrier Diode
19) Vacuum Diode
20) Gunn Diode
21) Point Contact Device
22) Pin Diode
23) Avalanche Diode
Small Signal Diode
This diode is used for the signal. In this type of diode, the value of voltage and current is very small. But the frequency (Hz) is very high.
This diode working on milliampere and millivolt is used in small signals.
Remember- Diodes are usually available in three sizes according to the capacity. 1 ampere, 3 amperes, and 6 amperes. Its size also increases according to the ampere.
Large Signal Diode
This diode is used to convert AC supply to DC. This diode is used where DC supply is required. As it makes Rectifier Bridge and is used in equipment like chargers, inverters.
This type of diode is not used in high frequency. In this type of diode current is transmitted forward based but blocking voltage in reverse.
Light Emitting Diode – LED
LEDs are being widely used today due to the continuous up-gradation of light and it is playing a very important role in saving electricity.
Works on LED Forward Biased. This type of diode converts electrical energy into light. We get light by providing voltage to the Light Emitting Diode.
Led Visible and No visible both are available. LED is available in different colors. The voltage level is different for different colored LEDs.
Light Emitting Diode is used for Aviation, Lighting, Vehicles Head Lamp, Advertising Poster, Traffic Signal, Remote, and Camera.
Zener Diode
We can call Zener Diode a special type of diode. Because it is made for a special purpose. This type of diode works on Reverse Biased. Zener Diode is used where voltage regulation is to be done and constant voltage is required.
The P and N semiconductors used to make Zener diodes have very high doping levels. This diode is also used in the work of break down, hence it is also called break down diode.
Chlorens Zener invented the Zener diode in 1950. It is called Zener Diode after his name.
Constant Current Diode
From the name of this type of diode, its work can be guessed. This diode controls the current. Most of the diode’s design is voltage control. But this diode is designed to control the current.
This diode works on forward biased. Allows only a fixed value of current to pass through. And this constant remains. There is no up-down of current in it.
That is why it is called Constant Current Diode.
Schottky Diode
This is a special type of diode. Platinum and tungsten metals are used in this type of diode. In this, the semiconductor is made of metal as well as a P-N junction. In which N-type silicon acts more like anode. And the metal used in this acts as a cathode.
In this type of diode, the voltage drop is very less due to the formation of PN junction with the metal. Losses are also less due to less voltage drop. Its current capacity is also good and switching is also fast. That is why it is used in switching applications. Where a high frequency rectifier is used.
Tunnel Diode
For the manufacture of this type of diode, the impurity and concentration of the molecule are made very high. Usually, PN is about a thousand times higher than the junction diode. Then the tunnel diode is formed.
Metals like germanium and gallium arsenide are used to make this type of diode.
It was invented by Dr. Isaki, therefore, it is also called Isaki diode. Tunnel Diode is used in Ultra High Speed Switching, Microwave Oscillator, Relatioxation Oscillator, Logical Memory Device.
Avalanche Diode
Avalanche means lava. The lava produced when the earth trembles is called an avalanche. According to the work of this diode, it is named Lava.
This type of diode works on the principle of Avalanche breakdown on Reverse Biasing.
This diode is used for RF Noise Generation and Microwave Frequency Generation.
Transient Voltage Suppression Diode
This type of diode works as a protection device. Sometimes due to fluctuation or jerk in the circuit, the value of voltage increases greatly.
At such times, this diode protects the circuit.
This type of diode works like a normal diode. But when the voltage increases then its operation changes. And within microseconds, it isolates the circuit.
This type of diode is used in telecommunication, medical, microprocessor, and signal processing.
Gunn Diode
In this type of diode, there is no junction of both P and N. There is only an N region. Due to this, when the voltage in the circuit increases, the current also increases. And up to a limit, the voltage and current will be taken up and then suddenly it will go down.
In this, the diode does not overheat, so the heat sink is placed under the metal plate.
Laser Diode
The laser diode works in the same way as the LED. We can say that this is a bigger version of LED. It acts as a light emitter.
In laser diodes, different types of diodes are made according to the needs of different types of lasers.
This type of diode is used in a laser show, laser pointer, laser printing, fiber optic communication, CD, DVD, and bar code reader.
Pin Diode
A special feature of this type of diode is that it has three layers.
There is also a layer in the middle of the P N Junction. In which there is no charge of any kind. Due to the layer between P and N, the area of the depletion layer increases.
This type of diode is used in photodetectors, RF switches, and Noise oscillators.
Gold Dopped Diode
Gold is used in this type of diode, hence, it is called Gold Dopped Diode. Due to the use of gold, the leakage current is very less in it. It is used for smooth operation.
Photo Diode
This type of diode works on the principle of the electrical effect of light. That is, converts light into electric current. As soon as the light comes on it, if the light falls then it will flow the current, or else it will stop the flow of current.
The invention of solar panels has been inspired by this. The solar cells we are seeing today are a big form of the photodiode.
This type of diode is also called photodetector or photosensor.
In this article on Diode, I have tried to share all the information related to the diode. In which the function, types, and uses of diodes are described in detail.
Different types of diodes
- P-N junction Diode used as a rectifier
The diode conducts in one direction only when it is forward biased. The diode is used mainly for conversion of AC voltage into DC voltage. The process of conversion of AC voltage into DC voltage is known as rectification. The diode is used as a rectifier.
2. Varactor Diode: The diode has a variable capacitance for different reverse bias voltage.
3. Zener Diode:
Zener diode is used as a voltage regulator. The zener diode is connected in reverse bias.
4. Tunnel Diode:
Tunnel diode is used for microwave applications. The tunnel diode has negative resistance.it is used as an ultra high-speed switch. The switching time is the order of nanoseconds. Due to its negative resistance, it is used as a relaxation oscillator circuit.
5. Schottky Diode:
Schottky diodes are used for the following purposes.
1. Voltage clamping applications and prevention of transistor saturation.
2. Used for RF applications.
6. Light Emitting Diode: LEDs are used for illumination purpose.
7. Photo Diode: Photodiodes are used for the conversion of photon energy into electrical energy
8. PIN Diode
It has the standard P-type & N-type regions, but the area between the two regions namely intrinsic semiconductor has no doping. The PIN diode is used as an ideal radio frequency switch.
9. Gunn Diode
Gunn diode is a PN junction diode, this sort of diode is a semiconductor device that has two terminals. Generally, it is used for producing microwave signals.
10. Laser Diode
The laser diode is not similar to the ordinary LED (light emitting diode) because it generates coherent light. These diodes are used in applications like DVDs, CD drives and laser light pointers for PPTs.
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