Intro

So this is my attempt at a simple, in fact very simple home automation device that ANYONE
can use, and almost anyone can make.
I am actually seriously considering manufacturing these in bulk (well something similar)
and selling the whole lot as a managed service for about a tenner a year. (please let me
know if this would be of interest to anyone)

Anyway, so this is my attempt at cheap home automation for the masses, I hope you like it.

If you like the look of these pictures:

then read on...

....A little bit about this site

I didn't use anything other than good old notepad to design this site,
dreamweaver is great - but you don't need it...

Design

• Connect it to a socket, light or any other appliance and use it to montor it.
• Attach to a solar panel or LDR to monitor light levels.
• Connect a pair of probes and detect water (plants, rain, leaks etc...)
• Connect to a PIR or Reed switch for security,
• Connect to a smoke alarm for fire protection,
• Connect to a pressure mat etc....

Note, these are all links to external sites

A managed switch, router, firewall, anything with an ethernet port and some kind of web
interface was what I was after, but it had to be cheap... and small....
Then I came up with the idea of a print server... Print servers are ideal, they use
very little electricity, are designed to be switched on all the time, can respond to
a ping and better still have a in-built webserver too. I did a bit of googling around
and saw them for as little as a tenner on ebay. Oh and they are tiny too!
I had three ideas for this project:

• The first was that I could break or short the transmit pair on the incoming ethernet
  cable to the print server.
  Obviously with these shorted or broken the device would be unable to respond to
  either a ping or a http request.

• The second was just to break the power to the device

What I really wanted was a way of getting a response from the unit to confirm that it
was either in one state or another, that way you could be sure of what was really going on.
That's where my third idea comes in.

• The third idea was to fool the print server that a printer was really attached to it,

I did a bit of reasearch, and it appears that pin 13 of the connector is used for
this purpose. Take the pin high (i.e apply 5volts to it) and the server thinks that
the printer is on_line,
take the pin low (i.e remove the voltage)and the server thinks that the printer is
off_line.
As all I have to do is apply and remove 5volts, I can just find 5volts
somewhere and route it through a switch. Close the switch and it appears that the
printer is on_line, open the switch and the printer appears off_line. As I say, this
status is reflected in the web interface, so a simple script should be able to poll
this page and parse the printer status and then use this information for something
useful

Construction

One thing's for sure though, this device will never be plugged into the back of a
printer. I'll soon have chopped it up into something far more interesting.
Details here: Edimax PS-1206P

Ok, so let's get the lid off one of these....
I just love taking stuff apart, but taking brand new stuff apart is especially fun for
me, it just seems so wrong!!
There are a couple of phillips head screws on the bottom and once these are removed,
the case just pulls apart, although you need to squeeze the sides a bit as the two
halves clip into each other.

I was pleasantly surprised with the inside of this unit, it was very well put together.
The lord only knows what all the bits are for, I guess there is a processor in there,
some memory, a bit of I/O and other stuff I don't understand.

Now, you could keep the big 36pin centronics socket on the print server and just get
hold of the matching plug to connect to it, but these are quite bulky and it seems a
bit over the top especially considering we only need to connect to 2 of these 36 pins.
I decided to cut the socket off... No, I didn't do it with an axe, it does look a bit
rough at the moment though:

I then desoldered the individual pins from the board and made up a little metal plate
to block up the hole left from the missing socket. I drilled a couple of holes in it
and connected a pair of screw terminals.
A bit of 2 part epoxy and some heatshrink and you have this:

Pretty neat eh?!
So that's the working prototype, with a bit of luck, bridging those two screw terminals
will return an on_line status, and leaving them open will give an off_line.
So it's time to test....
Note: The pictures above show the connections to pins 35 and 36, this is
INCORRECT, subsequent testing showed that I actually needed pins 13 and 19.

Here is the print server on my stairs, plugged into my network, with a bit of wire in
place to bridge out the pins for test purposes.

I decided to measure the power consumption, and I was pleasantly surprised at what I
found, it only uses 6watts, which isn't very much at all is it?
(At 10p per kwh, it'll cost about 5 quid per year to run)

As I said above, I'm going to poll my server with a HTTP request and collect the
printer status, but if you want to just see if it's there by pinging it, then you
can use ping to montior it, using something like:

date
n=1
 
while [ $n -lt 1000 ]
do 
	ping -n 1 server_ip 
	echo $n
	let n=n+1
done  
date

#!/usr/bin/bash

user=username
password=password
url=server_url

wget --quiet --http-user=$user --http-password=$password \
        --proxy=$proxy $url

grep Off_line printer.htm > /dev/null

if [ "$?" == "0" ]
        then echo "Offline"
        else echo "Online"
fi

rm printer.htm

wget --keep-session-cookies --http-user=username \
--http-password=password --post-data=message \ 
http://twitter.com/statuses/update.xml

wget --keep-session-cookies --http-user=user \
--http-password=password --post-data=message \
http://twitter.com/direct_messages/new.xml

ip nat inside source static tcp     extendable

#!/bin/bash

## Web Get Parameters
user="admin"
password="1234"
url="http://ip_address/printer.htm"

## Twitter Parameters
t_user=user
t_passwd=password

## Other Parameters
status="closed"

while true
do
        old_status=$status
        wget --quiet --http-user=$user --http-passwd=$password $url


        grep Off_line printer.htm > /dev/null

        if [ "$?" == "0" ]
                then status="open"
                else status="closed"
        fi

        rm printer.htm

        if [ $status != $old_status ]
                then wget --quiet --http-user=$t_user \
                --http-passwd=$t_passwd --keep-session-cookies \
                --post-data="user=twitter_username&text=message" \
                http://twitter.com/direct_messages/new.xml
        fi
        sleep 1
done