Our Home Control System


This page details our current (and planned) home automation implementation. The purpose of this page is to share our home control implementation with other people interested in home automation. Our current system includes wireless security and control, X10 and video generation and distribution. This page assumes a familiarity with X10 systems and modules. (For information on X10 see X10-COM.)


History of our Home Control
Description of the Current System
Diagram of Home Control Systems
Explanation of System Diagram
Example Home Monitor Screen
Explanation of Home Control Monitor Screen
Current Status (Updated December 17, 1997.)
The Future
Questions or Comments?
Home Automation Links (Separate Page)

Last Update: December 17, 1997.


This material is Copyright © 1997 Craig Buchanan. All rights reserved. This page may be freely linked to.
Please send comments or questions to
mailto: buchananc@acm.org.

History of our Home Control

The evolution of our home control systems followed the path outlined below. The pros and cons of each system are described.

  1. Simple Light Scheduling
  2. Security
  3. HCS II
  4. Home Monitor


Description of the Current System

The parts of the system are as follows:

A complete diagram of the system is shown below. A sample screen from the Home Control Monitor is available here.


Diagram of the Home Control Systems


Explanation of the System Diagram

The diagram is broken into four parts: Security, Home Control, Home Control Monitor, and Video.

The security console implements the security system. It communicates with the security sensors and maintains the zone statuses. The security system also acts as an RF (radio frequency) gateway for the home control system. It receives wireless X10 commands and forwards them to the power line. A “Smart RF Repeater” is used to give the security console increased range. The security console was modified by bringing out the digital zone and alarm status to an external connector. The digital signals are conditioned and connected to digital inputs on the HCS II for monitoring.

The home control runs an XPRESS program made up of rules triggered by time, X10 events, security events and other inputs. The programs rules generate X10 commands and digital outputs in response to the triggers. The PL-Link maintains a table of the state of every X10 device and keeps the devices in the correct state. The HCS sends a summary of all device states including its own about once a second on its RS232 port. The RS232 port is connected to the Home Control Monitor. A phantom set of X10 house codes is used to let the HCS display canned messages on the Home Control Monitor. (The use of X10 codes make it easy to test as X10 controller can be used to trigger the messages.)

The home control monitor reads the HCS summary and updates a real-time display of the home control system. (The display is explained in the next section.) The monitor is created by an Atari Falcon030 running in low resolution (320x200x16) in NTSC out mode. (320x200 was chosen as it produces a very stable, non-interlaced picture.) The NTSC signal is fed into a UHF modulator tuned to cable channel 78. Channel 78 was chosen as it was not used by our cable service.

The video system combines cable channel 78 from the home control monitor with the local cable signal. This signal is then distributed throughout the house. This allows the home control system (X10, Security, HCS Internals, HCS Network etc.) to be viewed from any television in the house.


Example Home Monitor Screen


Explanation of Home Control Monitor Screen

The monitor screen currently has 5 parts: Banner, X10, Security, Network and Messages.

The Banner displays the HCS date and time, along with the header character of the last HCS message. This character changes constantly and shows communication is taking place. (Current message header character in the image is "*"). 24 hour time is used.

The X10 box displays the states of the X10 house code being monitored. The descriptions and states are displayed as follows:

Line is blue for off, purple for on.
Bright colour: state has changed in last 2 minutes. (Bright blue or purple.)
State: `*' for on, `-` for off.
Shows time of last change in format HR:MN.
Shows day of last change if greater than 24 hours have past in format MN/DY.
(The X10 descriptions come from a configuration file. )

The Security Box displays the states of the security zones and shows if the security system is armed. The display is identical to that used for in the X10 box with the addition of the “Armed” and “Unarmed” display.

The Network Box displays the communication states of the HCS links. Currently there is only one link, the PL-Link. The states are displayed as follows:

State: Check mark for OK, Clock for time-out, and a bell for errors.
Shows time of last change in the same way as X10 and security.

The Message box displays messages from the HCS II. The HCS II XPRESS program has been set up to use a set of unused X10 codes (the “F” house codes) to trigger messages on the home control monitor. When an F code is turned on the message displays in a manner similar to the X10 box. Sixteen messages are currently supported and 4 messages can by displayed at the same time. The messages are currently used to show the “state” of the HCS II. Example states are “Welcome home”, “All off” and “Fish on”.

The monitor software was custom coded in Pure C. It is a TOS program (it doesn't use GEM). All output is graphical and was designed to have a modern 3D interface look. All three system fonts are used.


Current Status

As of December 17, 1997:
My cable television service continues to add channels. The open channel I was using, 78, and its neighbors are no longer free. This didn't leave any empty channels for the home monitor to use. So along with ordering a second modulator for the CD player I ordered a low-pass filter to free up cable bandwidth. The filter I choose removes channels beyond 64. (It's a Channel Plus, LPF-470, low pass filter: passband 20 Mhz to 468 Mhz.) On my cable service these are all scrambled pay channels which I don't subscribe to so I'm not losing anything. The filter goes between the cable service and the signal combiner.

I decided to try a digital video modulator for the CD player instead of an analog modulator. (It's an MM70 modulator from NetMedia.) Billed as "World's smallest modulator" it's a tiny black box that is easily programmed by pressing a button with a paper clip. The digital design is easier to setup and delivers a better picture than the analog modulator. The digital modulator was more money than the analog modulator but it's one of the least expensive digital modulators. I'm testing the new modulator on the home monitor as I haven't installed a cable run to the stereo cabinet yet. (Drywalled ceiling and walls in the basement don't help.)

I finally moved the RF security monitor away from the HCS II using an ordinary VGA extension cable. This has completely removed the RF interference problem. (The installation simply isn't as neat and compact anymore.)

As of October 1, 1997:
More progress on selection of CD and operation of stereo components via televisions in the house. I checked back on the availability of the Pioneer PD-F1006 in the beginning of September. I found they were in stock and ordered one. I installed it, loaded all our CDs and programmed in the titles (using a PC keyboard plugged into the front of the unit.). CDs can now be selected by scrolling through a list on a colour TV monitor. The next steps will be to get another modulator and add the CD player as a television channel in the house, and to install some IR repeaters.

The monitor computer has locked up on occasion, the display is left on screen but it doesn't update. (The time of lockup is frozen on the display!) The lock up happens randomly, sometimes within a day or two, sometimes after several weeks of constant operation. When this happens the computer must be restarted by reset or by power toggling. (The machine needs no further intervention after being turned on.) Thinking about this problem generated an obvious solution: the HCSII should monitor the home monitor computer and power toggle it if it locks up. I modified the home monitor program to toggle the state of a printer port line once every five seconds. Now I need to wire the printer port line into one of the HCSII direct digital inputs and update the HCSII script to watch for the toggle. At the moment the monitor computer has been running flawlessly for a few weeks now so this effort has become a low priority. (A watched pot never boils...)

As of August 25, 1997:
A new (used) computer has replaced the Falcon030. A used Atari 520STFM with 2.5MB of memory was purchased at MIST atarifest. The new computer is located in another room and RF interference hasn't been a problem. The monitor program has been modified to allow the colours used to be specified in the configuration file. This was necessary as the colours produced by the old 520 aren't as saturated as on the Falcon030.

In the "Future" section I mentioned automating the stereo system so CDs could be viewed and selected from any television in the house. This shouldn't be necessary as I have found a CD Jukebox that produces a video signal for disc management, the Pioneer® PD-F1005. Our stereo is already distributed from the living room to the kitchen, family room and gazebo. Using a video modulator and some infra-red repeaters with the PD-F1005 would allow the CD to be selected on a television in any room. According to catalogs on-line and otherwise the F1005 is being replaced by the F1006 which allows a PC keyboard to be used to enter CD titles. Unfortunately I can't find a F1006 anywhere, it would appear Pioneer® hasn't shipped any yet. The opposite approach is to use a PC to control the jukebox. PC control software, and a description of the PD-F1005 is available here: Wintek Home Jukebox , Pioneer® CD Changer Specs. A link to the PD-F1006 is here: Crutchfield - Pioneer Home Audio/Video Features and Technology.

As of July 22, 1997:
An RF shield has been added to the home control system to prevent interference with the RF security system. A disposable tin lasagna pan was cut to fit and screwed over the circuit boards on the home control panel. The pan was lined on the inside with duct tape to prevent any possibility of electrical shorts. This seemed to solve the RF interference problem.

The house cable system has been modified to send the new channel throughout the house. A new cable run (of RG6/U) was run from the home control panel to the exterior of the house where the cable company's signal enters. A signal combiner (a splitter used backwards) was used to add the new channel to the existing cable service before the signal was split and sent throughout the house. This installation had the advantage of requiring only a single new cable run.

The video modulator was added to the home control panel and the distributed video system was tested for about 24 hrs. Reception was good throughout the house. Unfortunately the modulator added still more RF which made the security system work even more poorly. In the test the Falcon030 (which creates the video signal) was located in another room. Given the fact that in the final installation the computer will join the home control panel and boost the RF level even higher the security console will have to be moved. The next test will involve using a VGA extension cable (the connection between the security console and the HCS II uses VGA connectors) to place the security console well away from the computers and modulator.

Prior Status:
The system as described has been constructed and programmed. The HCS II is controlling the house lights and appliances and the security system is working. The home monitor is working but has not been dedicated to the task at this point. (The intention is to dedicate an old Atari 520STFM or 1040STFM instead of using the Falcon030.)

Still left to do is to re-route the house cable installation to go to the home control panel before being distributed throughout the house. One problem remains however, the security RF signals seem to have trouble getting through to the home control panel. The symptom is that over time the security console seems to forget about several of the sensors (they don't show up on the panel - lights are off when in install mode). The "Smart RF Repeater" was purchased in the hopes of alleviating this problem.The control panel is in an electrically noisy environment, tests are underway to determine if:

Several options exist including moving the control panel, shielding the HCS, and remotely monitoring the security console. The re-routing of the house cable will wait until this problem is sorted out.

(If anyone has experience with this type of problem on a Powerhouse wireless security system please send me an Email.)


The Future

Many enhancements to the current system are planed or are being considered. Items being considered include:

Home Control and Monitoring via the Internet

A key enhancement is to place the system on the internet. That would allow us to easily monitor our home from work or anywhere else with an internet connection. While it's possible to implement much of the same functionality with a telephone interface for the HCS II, a live net interface would allow pictures to be viewed. (Sound monitoring would also be planned.)

A first step would be to place a one-way monitor on the net. A simple approach would be to setup a connection which would FTP the status display as a graphic file to the web server. A frame grabber could also be used to produce graphics from security cameras which could also be uploaded on a periodic basis. The second and more useful step would be a two-way link where commands could be issued via a browser and executed by the home control system. Obviously security would be a major concern in such an implementation.


Questions or Comments?

Any questions or comments can be directed to mailto: buchananc@acm.org.


This material is Copyright © 1997 Craig Buchanan. All rights reserved. This page may be freely linked to.
Please send comments or questions to
mailto: buchananc@acm.org.