This project is very important for PC communication with machinery. We know that today is the world of automation. There is increasing competition making it necessary to make it necessary to use reliable, low cost and accurate automatic system. With the help of this project we can control the all our factory machines with our PC with out the need of any control panel there will a small control panel for control of different switches. We will control the appliances with parallel port moreover we will use wireless  technology. For wireless system, we will use RF technology. We will attached RF txer and RF rxer with the PC’s Parallel port and  RF Rxer with different relays and Devices .we will use optocoupler  at the end of PC parallel port.

 

First component of this project is opto-coupler. IN this project we use ic 817 as a opto coupler . 817 is a 4 pin IC. Pin no 1 and 2 is input pin and pin 3 and 4 is the output pin. Pin no 1 is connected to the input signal and pin no 4 is acts as a output pin. When  high signal is connected on the pin no 1 then Internal infra red led connected to the pin no 1 is switch on and so  focus on the  photodiode connected inside the  optocoupler. Now due to this optocoupler is on and negative output is available on the pin no 3. This negative output is connected to the inverter IC.  Note that in this project we use four optocoupler circuit to control the four output circuit. So when all the signal is coming then four  output from the optocoupler is connected to the  inverter circuit .  We use a inverter in this project because we require a positive output at a result. Inverter in this project converts the negative voltage into positive voltage.

Emitter of the NPN transistor is connected to the negative voltage and collector is connected to the relay coil through positive voltage. Here NPN transistor work as a  switch in this project. Now when positive signal is connected to the  base of NPN transistor , then NPN is on and  relay connected to the collector point is  also on. PARALLEL PORT OPERATION

 

The original IBM-PC’s ParallelPrinterPort had a total of 12 digital outputs and 5 digital inputs accessed via 3 consecutive 8-bit ports in the processor’s I/O space.

 

• 8 output pins accessed via the DATAPort.
• 5 input pins (one inverted) accessed via the STATUSPort.
• 4 output pins (three inverted) accessed via the CONTROLPort.
• The remaining 8 pins are grounded.