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Computerize Your Room/Home (74LS154)

2017-07-01 11:27  
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So you`ve read about my Computerized Room or have seen
those nifty home automation products advertised in the back of
electronics magazines? Or perhaps someone you know has done
something similar. At any rate, you have decided to try it
yourself. The first thing I will say, however is that it is not

You will first need a computer, but since your reading this, I
assume that you already have that taken care of. Second, you
will have to buy about 20 IC`s and a very expensive ISA
experimenters prototyping board. These boards cost anywhere from
$16 to $45, and can be purchased from your local electronics
store or from Jameco Electronics (See Where To Get Parts).
They have a fairly wide selection. Buy the 8 bit version, the 16
bit varsion is not needed for this project.

Since this is a major project, it will be presented in
sections, starting with the Simple Parallel Port Interface. The 8
Bit Output Card will come next, followed by the 8 Bit Input
Card. All three interfaces came from the book “The Robot Builders
Bonanza”, by Gordan McComb.

I must also stress that this is a major project and should not
be attempted unlesss you have a good understanding of
electronics. If done wrong, you run the risk of not only
destroying the circuit, by also destroying an expensive computer
as well. Double, no, triple check your work to make absolutely
sure that is free from errors before installing it in any

DISCLAIMER: I am not responsible for any
damages caused due to a lack of knowledge or mistakes in the
circuit when building and using these projects.

Now then, with that out of the way, on to the Parallel Port Interface.


This is about the most basic interface you will see. It uses
only 3 74376`s (74LS367). This interface provides 8 outputs (plus
3 address lines) and 5 inputs. This is usually enough for one
room, providing you make use of some demultiplexers and the
address lines. You could have up to 128 output lines using the
address lines, a 74LS138 and 8 74LS154`s.

Begin construction by mounting the IC sockets on the board. I
used a experimenters universal solder board due to the large
number of wires that must cross. If a PC board were used, you
would need either a multi-layer board or many, many jumpers.

Now, solder wires along the top and bottom of the board,
making all the connections betw1een the IC sockets. Do not
install the IC`s yet. Assemble the cable using 26 conductor
ribbon cable and a 25 pin crimp connector. You will have one
conductor left over so just “peel” it off. Connect the cable to
the board and wire it into the circuit. I used an 18 pin socket
to make connections to the outputs and inputs on the
interface easy. You could do the same if you like, or use a
terminal strip.

Schematic Of The Parallel Port Interface

interfac Computerize Your Room/Home

Parallel Port Pin-Out

port1 Computerize Your Room/Home



You operate the interface by sending bit patterns to the
printer port. BASIC, GWBASIC or QBasic are the languages of
choice since most computers already have them installed (in your
DOS directory). If you wish, you can download control softw1are
from my files section.

The command you use is the OUT command. The decimal address of
most printer ports (assuming LPT1) is 888. Use this with the OUT
like this:

OUT 888,X

X is a number from 0 to 255 that represents the binary bit pattern.

Although designed primarily to get data out of the computer,
the printer port has 5 input lines (on some computers it could be
less). You access these lines with the INP function. This time,
however, the decimal address is 889. The syntax of the INP
command is:


Y is the variable used to store the decimal value that is
returned. X is the port number, which in this case is 889.

You may also use the OUT command to send data to the address
lines. Just use address 890 instead of 888. Remember that there
are only 4 address lines.

OK. With the basic parallel port interface done, you can build the more advanced 8 Bit Output Card.


This is much more complicated then the parallel port
interface, mostly because of the address lines used by the
computer to send data to different devices plugged into it`s bus.

This interface is constructed on an IBM 8 bit prototyping
board. These are available from Jameco Electronics (see Where To
Get Parts).Connections are made with point to point soldering or
wire wrap. Note that if you use the wire wrap method the board
will require about 1/2 inch clearence on the connection side.

Use sockets for all IC`s. Begin construction by first mounting
the sockets. Depending on which board you buy, you might have
lots or very little space. Connect the IC`s together using either
point to point or wire wrap. I used a 36 pin connector to
facilitate connection to the back of the computer, but you can
use any other method. Whatever the method, install that connector
and wire it into the circuit now. You may now wire the
connections to the bus (the gold contacts on the bottom of the
card). If you need a reference as to what the bus connections
are, check out The IBM Bus Pinout (I apologize for the poor image
quality). It is a good idea to bypass power supply pins
with .1uf capacitors to avoid problems with interference, power
supply spikes, etc. Triple check your work before installing the
circuit in any computer. The simple circuit to connect the
interface to relay`s is showen after the schematic.


out Computerize Your Room/Home



IC Power Pins

The power connections were left off the schematic for clarity. Here they are:


Relay Driver Circuit

relaydrv Computerize Your Room/Home

Controlling The Input And Output Cards

Controlling the cards is straight forward, using the basic INP
and OUT statements as explained in the Simple Parallel Port
Interface. The only difference is the address. The address for
the input card is decimal 701 while the output card is
decimal 703.

Choosing The Right Computer

This is the last section of this document. Choosing the right
computer is not that big of a concern. Anything from an old 8086
to IBM`s new Deep Blue supercomputer will work. Just make sure
that you triple check your work before installing it into any