What is a relay and which one should i use ??

https://www.edaboard.com/threads/53996/ thsi thread doesnt serves my purpose.

i need to make a motor rotate with an external battery of 9 v caonnected in series with the motor and the realay !~.. and also want the other circuit to be connected to the serial post of the computer.

the pc supplies 5v and the externmal battry that i have attached is of 9v(to drive the motor.)_

what actually i want to do. ???
i have a programe in C language which allows me to send dc 5v signal to data pins of the serial port ! so i want that when i send the 5v signal then the relay completes the external circuit and the mortor starts running !

so which relay will solve my purpose.?? really confused being a computer science enginnering student.
seeking help !!

and moreover i need not convert 5v to 9v ! so dun get confused by that . 9v is in the extetrnal circuit and has no connection with the serial post !

Relay is nothing but a switch in simple sence. You can know about relay from wikipedia... https://en.wikipedia.org/wiki/Relay

Since its a low voltage operation and the driving of motor is done by a logic 5v source, I say you can use both MOSFET and electromechanical devices as a relay.

If i got your point you have to use this:



You have to connect the battery ground to the serial port ground in order to work.

In ur case, there is no use of relay....u can use ic inrtead of relay....

Using Ic L293D u cam control 2 dc motors....u can download data sheet and easily can operate this ic....

I also had xperience with this ic in 2nd year of engineering when i made remote controled car....

Remember ic L293D

refer datasheet n go through it....best of luck