I didn't set out to invent a mass producible product so I didn't want the expense of a dedicated computer or touch screen or the time investment to program it.  I thought the notion of logging on to a computer to turn on a light or check to see if the garage door was open kind of defeated the intent of making life simpler.  The furnace already has a programmable thermostat and the outdoor Christmas lights use their own light sensitive controller.  I don't see all that much in a house that really needs to be automated, especially since programming the automatic controls takes time, more time that walking over and turning on the light.  And there is the expense of implementing that.

I did see the value, however, of knowing the status of the house and having that readily displayed. Thus, the caution and warning panel (similar to the ones in the Apollo command module and the space shuttle).  I use a panel of lighted pushbuttons (that I acquired on eBay for a steal!).  They have LED lamps that light green to indicate status like "mail in"; yellow to indicate caution like "porch activity"; or red to indicate warning like "front door unlocked".  Also, by the indicator being off the opposite is indicated.  Instead of having the yellow or red indicator light green when the status is clear, the lamp is simply off.  This results in less "indicator overload" as the indicator is on only to indicate an action item, as opposed to also indicating that no action is needed, which is the default condition.  Some lamps also flash to bring more attention.

Some of the indicators require that I reset them by pressing the display panel button.  For instance, when the doorbell is pressed the "doorbell" indicator is set on and remains on until the button is pressed.

The panel is located on a kitchen wall visible while entering the house or leaving.  It is small enough to not be obtrusive, yet large enough to be functional.  And, since my wife doesn't like me putting holes in the wall, it was a compromise so I could even do it.  You might snicker at this last point, but I'm willing to bet there are issues of too much technology dominating the house, and the reticence of some to put up with any more unless done tastefully.

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I'll describe below each of the indicators I used and why I did it that way.  This system has been operational since 2004 and it has become indispensable .


The garage door indicators show yellow when the garage door is open.  This is detected with a magnet and reed switch.  In addition, the lamps will flash if the door is open when it is dark outside.  During the day the garage doors may be open as I'm likely to be around but knowing that is valuable.  However, after I've come in for the night and especially when it is dark out, I want more attention being given to the fact that the garage door is still open so flashing the indicator accomplishes that.  Twice previously my garage door stayed open all night.

The front door must have the deadbolt locked or this indicator will flash red.  Most alarm systems just detect if the door is closed, which is better than nothing, but this system requires it to actually be locked.  This is implemented by drilling a hole in the end of the deadbolt and inserting a magnet, and then installing a reed switch in the door jam such that when the deadbolt is locked the reed switch closes.  It is important that the locked indicator responds to a closed circuit.  Recently the indicator was flashing red even though the door was locked.  It turned out a mouse had chewed thru the wiring in the basement ceiling.

The deck door has a more complicated latching mechanism requiring the use of an opto-reflective sensor to detect when the latch hook was inside the door frame.  But since the latch was affected by sunlight a smart sensor had to be installed that nulled out the effect of varying light levels, based on some sensors I designed previously (1).

The driveway activity indicator glows yellow when the driveway motion detector senses activity.  Once activity is detected that lamp stays on until reset.  This is handy as it signals when the paper comes in the morning when the delivery person's car drives in.  However, the sensor also notices the ducks that sometime waddle by or other animals.  So, to make the paper indicator more reliable a low cost atomic clock is used to automatically reset the circuit at 5:30 a.m.  The atomic clock was chosen since it is always accurate and automatically changes its time with  daylight savings time.  I never have to worry about resetting it.  I tapped off the piezo alarm drive to get the alarm signal.  Simple, but effective.

The doorbell indicator flashes yellow and stays on until reset.  This is useful (along with the porch activity detector) to indicate if someone was at the door while I wasn't home.  Often packages are left on the front porch, but I come in thru the garage and don't notice the porch.  To detect the doorbell button press I didn't want to connect to the bell circuit directly, so I monitor the current spike thru a simple transformer that the doorbell wiring is looped thru.

The porch activity indicator like the doorbell indicator also flashes yellow when someone comes up on the porch.  This is handy as mentioned above to note that someone was there at some point, perhaps to deliver a package.  It stays latched requiring me to reset the circuit.  It is implemented with a wireless motion detector as it would have been difficult to hard wire the sensor in.

The shop power on indicator flashes yellow when my shop's power is on.  This reminds me to shut down at bed time and not leave a soldering station on unattended.

The stove on indicator flashes red when the stove or oven is on.  This works with an electric range, another system would be needed for a gas range.  To detect the range being on current flowing to it is monitored.  But, since the power cycles on and off to maintain the temperature timing loops had to be identified and implemented that kept the light on even when the coil cycled off.  Thus, the lamp may flash for a period after the range is turned off since the controller doesn't know when it is switched off or just cycling off.  I know of at least two people who had fires in their kitchen when they forgot and left their stove on.  I didn't want that to happen.

The water flowing indicator lights yellow when water is flowing.  This is detected by monitoring the needle on the water gauge inline with the water feed.  An opto reflective sensor detects when the fast moving needle is in motion when water flows.  It is also based on the sensor I previously designed (1).  This has already paid for itself as once a seldom used toilet in the basement just broke and kept running.  It was noticed that water was flowing even tho there shouldn't have been so a little detective work found the broken toilet.

The water softener salt low indicator glows yellow when the salt gets below a certain level.  This is sensed with a Polaroid ultrasonic sensor.

The change furnace filter glows yellow after so many hours of run time have occurred on the furnace filter.  This is detected by monitoring the air pressure drop in the return air duct and requires no wiring to the furnace or controller itself.  I remember one house I moved into, I checked the furnace filter and it was obvious the previous owner had never changed it.

My shop is in the basement and occasionally I'll open the window.  Since it is below ground level rain would pour in if left open so it is monitored with a magnet and reed switch.

The power fail circuit is an ac voltage relay wired as a latch.  When the power goes off the relay drops out and stays off and until the button is pressed to reset it.

The washer and dryer are monitored and when they are done the indicator glows green.  When the door on the machine is opened a Radio Shack Mail Guard sensor modified to use reed relays and a magnet on the door resets the lamp.  Thus, the lamp is on until the clothes come out of either the washer or dryer.  The operation of the machine is sensed with a current sensor wired inside the breaker box.  Since the cycles vary on the machines once they have been on long enough to be well into a wash or dry cycle the lamp is turned on even tho the cycle is not really complete.

The dishwasher is also monitored and when it is cleaned this lamp glows green.  Between my wife and I it wasn't always clear when the dishes in the dishwasher are clean or dirty since we would take a dish out when needed without unloading all the dishes.  Now with this indicator we know.  This system uses two sensors, one to monitor the current to the dishwasher and the other to monitor the dishwasher's door.  After the dishwasher has been running for a while the lamp comes on and stays on.  It stays on until the door has been opened for a long enough continuous time that would occur when the dishwasher is unloaded and maybe reloaded. Momentarily opening the door won't reset the light.

The mail in indicator uses a Radio Shack Mail Guard transmitter in the mailbox to send a code to latch the indicator on green.  Once the mail is retrieved I have to reset the circuit by pushing the button.

I use a battery powered lawn mower and monitor when it is recharged and indicate this with a green indicator.  I have solar panels intended to recharge but they turned out to not have enough voltage, so they power the home monitoring system instead.  I have had good experience with the Black and Decker battery powered mower and will probably never use gas again.

The stereo speakers upstairs indicates the remote speakers are connected to the living room speakers instead of my shop's.

The video switch active has not been implemented and there are a couple others that aren't used yet either.

The intake air vent open indicates the outside air vent intended for the gas water heater is open.  The water heater uses a forced air vent so the blower motor's operation controls a flapper on an air vent nearby the water heater.  Previously the vent was open to the outside air and in the winter cold air would pour into the basement even when the water heater was not running.  Now it only does when needed.


The sensors are built around 8 pin Microchip PIC microcontrollers.  There is no big single chip controlling or monitoring everything.  The outputs from the sensors are fed into 16 bit shift registers.  The data on the inputs are shifted out and sent serially to shift registers in the display panel which have the capability to directly drive the 24 volt LEDs.  It is simple and has low parts count.

I have a smaller satellite display panel in the shop for things like the doorbell or driveway activity.  There is also a satellite display in the garage which uses 7-segment LED displays to form words to indicate up to 8 conditions that i would need to know about before driving away.  For instance, if the stove is still on the display would show 'Stov' and I would go in and turn it off before leaving.  To conserve energy the display is only powered when the garage door is open.  If it is close dI'm obviously not driving anywhere.

I did have a problem with noise generated on the ac power line whenever the microwave in the kitchen ran.  I had to add timing and checking to the sensor's microcontroller software to get around the noise problem.  Short of an extensive and probably expensive remedy there wasn't anything I could think of to do.  I remember reading an article in EDN about power line noise, and indeed it is real.



(1)  A Non-Contact Infrared Bumper     http://www.dtweed.com/circuitcellar/xbarania.htm