What is Diode?

Diode is an electronic component, which allows current to flow in one direction

It has two Terminals; Anode & Cathode.

It is used in two modes; Forward bias and Reverse bias.

1.        Forward bias: When +ve Voltage is connected to Anode and –ve to Cathode.

2.       Reverse bias: When -ve Voltage is connected to Anode and +ve to Cathode.

Zener Diode & Photo Diode are used in reverse bias mode.

In Forward bias, it shows least resistance and in Reverse bias it shows higher resistance.

Some diodes are used in forward bias and some are used in Reverse bias.

There are many types of Diodes, and according to the requirement, they are used.

 

Type of Diode

1.        Normal Rectifier Diode

2.       Light Emitting Diode (LED)

3.       Zener Diode

4.       Schottky Diode

5.       Photo Diode

6.       Transient Voltage Suppression Diode (TVS)

 

 

Rectifier/Power Diode

This is also known as Power Diode

This is used for rectification in power supplies

This is used in Forward Bias

1N4001 is a power diode used for rectification

Other are also available, 1N4002/03/04/05/06/07

 

Light Emitting Diode (LED)

This is used in many applications for output indication

This is used in Forward Bias

These are available in various colours and sizes

 

Zener Diode

This diode is used in low power voltage regulation

This is used to protect circuit from overload

This is used in Reverse Bias

These are available in different voltages

 

Schottky Diode

This diode is also known as Schottky barrier diode, hot-carrier diode

It functions in forward bias

It has a low forward voltage drop

It performs very fast switching action

Voltage clamping, Rectification in SMPS

 

Photo Diode

This diode converts light into electrical current

This is also known as Photo-Detector, Light Detector, Photo-Sensor

This is used in Reverse Bias

 

TVS Diode

This is used to protect electronics from voltage spikes induced on connected wires

This is also known as transil, thyrector

It is a clamping device

It suppresses all overvoltage above its breakdown voltage

These can be unidirectional or bidirectional

 

 

What is Relay?

Relay is an electrically operated switch that opens and closes the circuit by receiving electrical signal from the outside source 

Relay Type:

Ø  Relay technology is divided into two categories

1. Movable Contacts

2. No-Movable Contacts

 

Mechanical Relay

                

 

Solid State Relay

                    

 

Relay Types:

Mechanical Relay

Ø  This relay has contacts that are mechanically actuated to open/close by a magnetic force

Ø  This magnetic force is produced by a coil which is excited by the electric current

Ø  Due to movable part it creates noise during operation

 

Solid-State Relay

Ø  This relay does not have mechanical contacts to control outputs

Ø  There are electrical switching elements such as Triac and MOSFET

Ø  Since no movable part is there so no noise it creates

 

Mechanical Relay- Advantages

Ø  It provides physical isolation between input and output

Ø  It can withstand higher voltages

Ø  These relays can tolerate short-term overload condition

Ø  Transients do not affect output of the relay significantly

 

Mechanical Relay- Disadvantages

Ø  Due to mechanical contacts its switching speed is slow

Ø  It has limited life span due to mechanical parts

Ø  These relays create contact-bounces which cause arcing

 

Solid State Relay - Advantages

Ø  It also provides physical isolation between input and output

Ø  Switching time is less as compared to the mechanical relay

Ø  Life expectancy is higher

Ø  These Relays offer greater reliability

Ø  No contact-bounce problems

 

Solid State Relay – Disadvantages

Ø  Resistance in the output circuit is normally higher as compared to an Electromechanical relay

Ø  It is not resilient to transient spikes and other overload conditions, like a mechanical relay, unless it is protected

Ø  A transient above the limits of the output device could destroy the solid state relay