delabs News Feed delabs Technologies Search delabs
Contact delabs
Design Service
delabs Technologies 
Search Contact Service

Simple Printer Port Interface, Input-Output - del20005

Printer Port Circuit to see the inputs logic state and drive a few outputs. The preset control program helps test out the circuit operation. Use safe 5V Levels.

This page triggered by  "Use of a PC Printer Port for Control and Data Acquisition" Printer Port Page of  Peter H. Anderson.

So i made some example circuits and VB programs for students. A demo Milli Volt source, Digital Voltmeter and Logic Analyzer examples for learning, are on these pages.  I have tried to derive power from PC itself in this circuit, Care should be taken not to short circuit or apply any voltages above 5V to PC Port Pins.

USB PIC a easy PC Interface

There are protection in all chips these days, but you may stress the limits, so design and use opto couplers to be on the safer side.

74HCT373 is the only chip used to interface the real world with the PC Parallel port. The Inputs to this chip are protected with Resistors and Zeners. 3 outputs of PC are also monitored using LEDs. This gives you a IO interface for experimenting. Below is a Preset counter simulation that you can use with this circuit for testing. Schmitt Triggers and Signal Conditioning may be required for Noisy and Non-Sandard Inputs.

Preset Counter Demo
PNG-Schematic     PDF-Circuit     DSN-Source
Simple Printer Port Interface, Input-Output - del20005
To view circuit click the Link of PNG or PDF, The PNG Image can be Drag Scrolled with Mouse.

The vb programs works well on xp-p4 and may not work well on win98-P2 (speed). Logic inputs in above circuit are floating add a 100K to ground for all 5 inputs if you want to use it as a logic probe.The Logic Analyzer Program is here . Demo Logic Analyzer 100KHz VB6 program with source code, can be tried with this circuit. An Example to get fast time in uS as vb timer min. 1ms is here

The design source is here A visual basic 6 program with source, to test this circuit and experiment is here Preset Counter Demo for Printer Port.

More Information.
Parallel port to drive a LED -read a switch
This page describes the use of a LED on a printer port, to indicate something, for instance while the PC screen is turned off or in screen save mode, like whether your server is still running,

Read Humidity and Temperature on PC

Data Acquisition & Control
Do you have an old PC lying around the house which absolutely no one wants? Then you can convert it into a dedicated controller. Communicate with the real world via the parallel printer port on your PC. Simply connect printer cable from computer to D25 connector on relay board