Electronics - Voltage and Current - Discussion

@Kowsalya.

The "push-button" has been utilized in calculators, push-button telephones, kitchen appliances, and various other mechanical and electronic devices, home and commercial.

In industrial and commercial applications, push buttons can be linked together by a mechanical linkage so that the act of pushing one button causes the other button to be released. In this way, a stop button can "force" a start button to be released. This method of linkage is used in simple manual operations in which the machine or process have no electrical circuits for control.

Pushbuttons are often color-coded to associate them with their function so that the operator will not push the wrong button in error. Commonly used colors are red for stopping the machine or process and green for starting the machine or process.

Red pushbuttons can also have large heads (called mushroom heads) for easy operation and to facilitate the stopping of a machine. These pushbuttons are called emergency stop buttons and are mandated by the electrical code in many jurisdictions for increased safety. This large mushroom shape can also be found in buttons for use with operators who need to wear gloves for their work and could not actuate a regular flush-mounted push button. As an aid for operators and users in industrial or commercial applications, a pilot light is commonly added to draw the attention of the user and to provide feedback if the button is pushed. Typically this light is included into the center of the pushbutton and a lens replaces the pushbutton hard center disk. The source of the energy to illuminate the light is not directly tied to the contacts on the back of the pushbutton but to the action the pushbutton controls. In this way a start button when pushed will cause the process or machine operation to be started and a secondary contact designed into the operation or process will close to turn on the pilot light and signify the action of pushing the button caused the resultant process or action to start.

@Anusha:
U get it na, that SPDT hav one input and Two output lines. The best example of SPDT is Relay. I will giv u bettr example, assume that u have relay of 6v, it hav two output normally open and normally closed. Relay hav its main input connectd to that normally closed terminal. Assume u hav connected a motor to normally open terminal. And there is nothing connected to that normally closed terminal. When u giv voltage upto 5.8v to relay, ur motor will not run. But as u giv voltage to relay of 6.1v ur motor which is connected to normally open terminal, will start to run. This is how relay works with the best example of SPDT swicth.

SPST Single pole, single throw One-way Two-way A simple on-off switch: The two terminals are either connected together or disconnected from each other. An example is a light switch.

SPDT Single pole, double throw Two-way Three-way A simple changeover switch: C (COM, Common) is connected to L1 or to L2.

DPST Double pole, single throw Double pole Double pole Equivalent to two SPST switches controlled by a single mechanism

@Sumita.

If we do parallel connections then we can provided 6. 1v supply to both the motors so that both can work at a time. But the problem is if you need to operate these motors separately then one should provide a switch so that we get option in-front of us, which is more suitable way.

Thanks sourav for the answer.

But can you tell me in the example you mentioned above, if another motor is also connected to the closed terminal of the relay (the previous motor also connected) , and we provide 6. 1volt, then which motor will turn on?

Answer is SPDT.

The basic theory is the moving contact of the switch is known as "Pole" & non-moving contact is known as "throw". So, from symbol we come to know that there is a single pole and double throw. Hence it is SPDT.

Single pole double through switch-spdt.

Single pole single through switch-spst.

Double pole double through switch-dpdt.

It means a single pole (point) can throw its connection to any of the other two poles. So its DOUBLE THROW.

@Usman : you can take a example of a relay where three terminals are there. Com, NO, NC. When common connects with NO it is open switch.

And when com connects with NC it is closed switch.

Just a calling bell or horn etc are the example of push button, where by until we press the circuit will be closed past and operate and while realizing it come back to normal position.

A push button is nothing but a switch which make a connection until we press or push the button as soon as button is released it comes to its normal i.e, open condition.