RS232
is a very old output port available in the computers. In the early days, all
the computers were having RS232 port as a standard one. But with the advent of Serial
Bus (USB), which is having more sophisticated functions and with less pins than
RS232, the traditional Serial port is gradually replaced by USB. Although
serial port has been completely removed in the contemporary laptops, desktops
still have serial port.
The USB relay controller board may have 4, 6 or 8 relays, comprising of a microcontroller,
DC power supply, serial port connector, and relay connector and obviously
relays. The board is associated with computer through RS232 cable. This cable connects
to the serial port or relay board at one end and the other end to the serial
port of the computer.
Software
is developed by utilizing computer languages such as C++, Delphi, or VB.
Through this relay control software we can send or receive data to relay
board through RS232 port. The software provides front end side of controlling
system. Some codes defining different commands are defined and inbuilt into
software and into firmware of microcontroller in order to understand the same
thing while communicating with each other.
The
command is then transmitted to USB relay controller through the serial port. Microcontroller on the relay board is
always ready to listen any kind of communication from the computer. As soon as
it gets the command, it is deciphered according to the agreed codes and ideal
action is taken. In our example, if any code is making Relay1 on, as soon as
the computer sends the code, the microcontroller after getting the code,
interprets the command and turns on Relay 1. The successful turning on of the
relay 1 is communicated back to the computer as a type of feedback.
