Simple Parallel Port Interface for Robotics

Although nearly obsolete, the parallel port (printer port) on the PC has the advantage of simplicity when interfacing with experimenter and hobbyist electronics (robot and android control) You can also use old computers for experimental set-ups; why risk that nice new machine you just purchased.

Simple parallel port interfacing circuits with programming info This is a .pdf document that has the schematics, photos and test programs, everything you'll need to build this interface. See the data sheets below for more info about the individual components (CMOS ICs, voltage regulator ICs, optoisolators).
Parallel port access under Windows source code and demo app. From "Getting Beyond the Box with Windows 95" by Craig Pataky, Circuit Cellar #74, September 1996
Data sheets for IC's (Integrated Circuits) you'll need for the parallel port are available below
LM7805 voltage regulator
ULN2803 darlington transistor array
CD4042 quad transparent latch
CD4051 Single 8-Channel Analog Multiplexer/Demultiplexer
CD4093 Quad 2-Input NAND Schmitt Trigger
CD4099 8-Bit Addressable Latch
Data sheets for opto-isolator (optoisolator) outputs and power handling devices are below. Note: The data sheet for the 2N6044 transistor is not available. You can use the TIP120 transistor instead or look for a higher power substitute. See the schematics below for more information.
4N38A opto-isolator transistor output
MOC3011 opto-isolator triac output
TIP120 power Darlington transistor
2N6071 sensitive gate TRIAC

This is the parallel port schematic.
It has 8 inputs, 8 outputs (each input or output is individually addressed),
a built-in regulated 5 volt power supply (power supply input unregulated 7 to 24 volts DC or AC)
and outputs that can handle up to 500mA. Best of all, you can build it in an afternoon for less than $15.
To see a larger image of the schematic click on the image below. A printable version of this schematic, along with programming information, is in the PDF file at the beginning of this list.
Use the "Back" button on your browser to return.

Here are two ways of controlling power greater than the 500mA limit of the ULN2803 using low-cost optical isolators.
You'll need one of these isolators for each high-power circuit you want to control (up to 8, one for each output)
Both circuits take a 5 volt DC input from the interface through a 220 ohm resistor (limits current to the LED in the opto-isolator).
Make sure you have the polarity correct for the LED in the opto-isolator
The first circuit controls DC power using a 2N6044 Darlington transistor (80 volt, 8 amp).
You can use a TIP120 (60 volts, 5 amp) Darlington transistor instead if you wish.
A relay is shown but a motor or other DC powered device can be used instead.
Use a heat sink on the transistor as necessary.
DC circuit control

The circuit below controls HIGH-VOLTAGE (117 volts) AC (alternating current) power with a triac.
It can take either an inductive or resistive load.
Make sure you construct this circuit in a grounded metal case and fuse it properly!
If you build this circuit I'll assume you know what you're doing and you won't fry yourself!
AC circuit control

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