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PC control wireless car



Components Required:-


IC 89C051

Relays 120 ohm 12 volt

Transistors 548

In4001 diodes

Parllel connector

Connecting wire:


7805 voltage regulator

transformer 12 v

cap 1000µf,470µf

crystal 11.0592Mhz

8.2 k and 330 ohm resist.

Push to on switch

Universal Programmer


Software Required:







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 need to make a small  program in C_++ . in this program 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.

Pin no 1 of the IC 4049 ( inverter) is connected to the positive supply. Pin no 8 of the circuit is connected to the negative supply. Pin no 3,5,7,9,11 is the input pins of this ic. Pin no 2,4,6,10,12 is the output pin no this ic. Signal from the  optocoupler is connected to the pin no 3,5,7,9 and output is available on  the pin no 2,4,6,10 . At the input point of inverter we connect  four resistance on each point to give a reverse voltage on the input pins. Now when inverter gives its output in positive  voltage then this voltage is again connected to the  base of transistor through resistance and one light emitting diode.  Here we use npn transistor as a relay driver. 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 Parallel Printer Port 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 DATA Port.

·        5 input pins (one inverted) accessed via the STATUS Port.

·        4 output pins (three inverted) accessed via the CONTROL Port.

·        The remaining 8 pins are grounded.



The standard IBM PC parallel port has 25 pins as shown above in the diagram. Its various pins have their unique features. These are enlisted in the table given below:


Simple circuit and program to show how to use PC parallel port output capabilities

Copyright Tomi Engdahl 1996-2000

PC parallel port can be very useful I/O channel for connecting your own circuits to PC. The port is very easy to use when you first understand some basic tricks. This document tries to show those tricks in easy to understand way.

WARNING: PC parallel port can be damaged quite easily if you make mistakes in the circuits you connect to it. If the parallel port is integrated to the motherboard (like in many new computers) repairing damaged parallel port may be expensive (in many cases it it is cheaper to replace the whole motherborard than repair that port). Safest bet is to buy an inexpensive I/O card which has an extra parallel port and use it for your experiment. If you manage to damage the parallel port on that card, replacing it is easy and inexpensive.

DISCLAIMER: Every reasonable care has been taken in producing this information. However, the author can accept no responsibility for any effect that this information has on your equipment or any results of the use of this information. It is the responsibly of the end user to determine fitness for use for any particular purpose. The circuits and software shown here are for non commercial use without consent from the author.

How to connect circuits to parallel port

PC parallel port is 25 pin D-shaped female connector in the back of the computer. It is normally used for connecting computer to printer, but many other types of hardware for that port is available today.

Not all 25 are needed always. Usually you can easily do with only 8 output pins (data lines) and signal ground. I have presented those pins in the table below. Those output pins are adequate for many purposes.

pin function
 2   D0
 3   D1
 4   D2
 5   D3
 6   D4
 7   D5
 8   D6
 9   D7

Pins 18,19,20,21,22,23,24 and 25 are all ground pins.

Those datapins are TTL level output pins. This means that they put out ideally 0V when they are in low logic level (0) and +5V when they are in high logic level (1). In real world the voltages can be something different from ideal when the circuit is loaded. The output current capacity of the parallel port is limited to only few milliamperes.

        Dn Out ------+
  Sourcing         Load (up to 2.6 mA @ 2.4 v)
        Ground ------+

Simple LED driving circuits

You can make simple circuit for driving a small led through PC parallel port. The only components needed are one LED and one 470 ohm resistors. You simply connect the diode and resistor in series. The resistors is needed to limit the current taken from parallel port to a value which light up acceptably normal LEDs and is still safe value (not overloading the parallel port chip). In practical case the output current will be few milliampres for the LED, which will cause a typical LED to somewhat light up visibly, but not get the full brigtness.

LED and resistor

Then you connect the circuit to the parallel port so that one end of the circuit goes to one data pin (that one you with to use for controlling that LED) and another one goes to any of the ground pins. Be sure to fit the circuit so that the LED positive lead (the longer one) goes to the datapin. If you put the led in the wrong way, it will not light in any condition. You can connect one circuit to each of the parallel port data pins. In this way you get eight software controllable LEDs.

The software controlling is easy. When you send out 1 to the datapin where the LED is connected, that LED will light. When you send 0 to that same pin, the LED will no longer light.




Applications :

Controlling machines from PC

Communication of machines from parallel port

Advanced robotics