Many home automation enthusiasts like to monitor if their car is home or “on the road” with their automation systems. One way this is accomplished is by using an X-10 motion sensor mounted under the steering column. When motion is detected (from the driver) a unique signal is sent that represents the presence of the vehicle. This method has many short comings though.

One solution would be to have the vehicle “broadcast” a unique X-10 signal when it is started and then broadcast another signal (at longer intervals) when the car is turned off.

This How-To will describe how to make such a unit using a “hacked” palm pad remote.

For starters you should be familiar with the How-To describing How To Hack A Palm Pad Remote, as we will be using this methodology here.

The basic method for this How-To is to use a timer that will continually send a “signal” or pulse every three seconds. A counter circuit will then “count” these pulses and output its own pulse after a specified “divide by” time interval has occurred. The short and long timed pulses will then each trigger their own unique X-10 codes via the palm pad remote.

Refer to this SCHEMATIC. (Allowing the Visio Active-X control will allow for enhanced viewing/zooming capabilities).

This shows a 555 timer on the upper left that will continually output a pulse approximately every three seconds. The timed output (duration and off times) are determined by the 56K & 200K resistors as well as the 10uF capacitor. This output feeds a counter chip (CD-4020) and a transistor (2N3904) that drives a relay which will give a contact closure to the palm pad remote.

Note that a four pole double throw relay will have its contacts either open or closed depending if the car is running or not (because its coil is connected to the car’s accessory terminal). This relay does a few functions, one is to either let the 555 timer trigger the contact closure for the palm pad or, let the output of the counter chip trigger it. It also will determine “what” contact will close for the palm pad (in this case it will short Diode D12 to Jumper 4 when the car is off and Jumper 1 when the car is on). This way a unique X-10 signal is sent from the palm pad whether the car is running or not.

The counter is a binary type with various “Q” outputs. Each output represents a “bit” or specific count interval. Depending on what “Q” output pin you choose to use will determine the number of pulses needed to “count” before that output will output a pulse.

For this case we chose output Q10 which will yield a pulse after 512 counts (from the input) are received. After that happens the counter will then reset to zero and start the count over. For our case this would represent 512 pulses that occur every three seconds (from the 555 chip) so the time interval before it will output a pulse from Q10 would be 3 seconds times 512 = 1536 seconds or roughly every 26 minutes.

You can select from a variety of counter outputs to determine the count interval you would like from the table on the right:

The power supply regulator circuit at the bottom of the schematic will insure that only 8.75 volts DC will be used for the components as well as the supply for the palm pad remote (the input voltage can vary up to 30 volts, plenty of overhead for a vehicles 12 volt system).

This circuit was prototyped and wired into a palm pad remote as shown below (top and bottom views):

One note to mention is that I did not have a 4PDT and used two DPDT relays instead.

I simulated the car starting and stopping by jumpering twelve volts on the Acc Terminal input. I also set the house code to “I” on the palm pad remote. HERE is the Homeseer log results obtained while testing this prototype. As you can see a house/unit code of I15 ON was received every few seconds when the car was on and a house/unit code of I15 OFF received every 30 minutes (count interval started immediately after the car was turned off, and continued counting every 30 minutes until the car was restarted).

These X-10 signals can now be used in Homeseer (or other software) to determine the occupancy status of the vehicle. One way to do this is to set up two events in Homeseer. One gets triggered on the I15 ON command and the other gets triggered on the I15 OFF command. For the ON event, set the “do not retrigger” block for something like ten minutes. Also set a variable (X-1 in this case) which will act like a flag for the code.

The code for this ON event will look something like the following:

sub main()

if hs.ison(“X1”) then

hs.speak “BSR is home”

end if

hs.execx10 “X1″,”on”,0
end sub

The code needed for the OFF event (which will be triggered one half hour after car is turned off) will then set the X1 device to zero.

There are probably other ways to implement this code to this hardware function as well.

Parts Listing:

Below is a listing of where to obtain parts for this project. Jameco Electronics was used to obtain most. Their prices are reasonable and delivery excellent (at least in the west coast).

* 555 IC Timer $0.27
* CD 4001 Quad NOR Gate $0.29
* CD 4011 Quad NAND Gate $0.29
* CD 4020 Binary Counter $0.49
* LM 317 Voltage Regulator $0.45
* Heat Sink Mounting Kit for LM317 Regulator $3.95
* Heat Sink for LM317 Regulator $0.39
* 2n3904 Transistor $0.09
* 1N4005 Diode $0.04 (3 each)
* 4PDT 12 V Coil Relay $6.95
* SPST 9 V Coil Relay $2.29
* 1.6K Resistor $0.99
* 270 Ohm Resistor $0.99
* 200K Resistor $0.99
* 56K Resistor $0.99
* 0.01 uF Capacitor $0.06
* 0.1 uF Capacitor $0.15 (2 each)
* 10uF Capacitor $0.06
* 330uF Capacitor $0.13
* Fuse Holders $0.79 (2 each)
* 0.5 Amp Fuse $0.20 (2 each)
* 14-Pin IC Socket $.08 (2 each)
* 16-Pin IC Socket $.09
* 8-Pin IC Socket $0.25
* PC “Bread-board” $3.29
* Palm Pad Remote $5.99

TOTAL COST = $31.89

Plus a housing of your choice and miscellaneous hook-up wire and solder.

This is by no means represents the ultimate way to build such a device, but rather was the first idea that popped into my head. Please feel free to add, enhance, criticize (but not to badly), etc… to this circuit.

One disadvantage the above circuit has is there is no OFF code immediately sent after the car is turned off. Also, I’m not sure how important it is to have an OFF signal broadcast from the car every half hour after it is parked.

Therefore I tested an alternative circuit that will broadcast an ON signal every few seconds when the car is on, then send about four or so OFF signals immediately when the car is turned off (and no signals sent after that).

Refer to this SCHEMATIC. (Allowing the Visio Active-X control will allow for enhanced viewing and zoom capabilities).

This circuit operates similarly to the above circuit except for the fact that no counter is incremented. Rather, when the car is turned off, an RC (resistive/capacitive) time constant (provided by the 100K resistor and 1000uF capacitor on the NAND inputs) allows the output of the NAND gate to remain high for a few seconds. Also the 4PDT relay is switched to its OFF position so an OFF X-10 code will now be sent from the Palm Pad remote.

This circuit was quickly built up (without the regulator circuit) and operated on a nine volt battery for testing this concept as shown here.

Again, I did not have the small DIP 4PDT relay and used that larger one temporarily during this bench test.

This circuit was tested by simulating the car starting and turning off by applying 12 volts to the 4PDT relay. HERE are the test results.

Note that this circuit uses a resistor that was not used in the above first circuit.

* 100K Resistor $0.99

Again, I do not propose that these two circuits represent the “ultimate” way to achieve this function. Also, additional features might be needed and added to this methodology. For instance, you could have a 12 volt relay coil connected to reverse lights and tie the contacts between the palm pad and these circuits so unique codes were generated for “forward” or “reverse” operation. Also, you might want to place normally opened magnetic contacts or a 12 volt motion sensor (normally opened) in your car and connect those to some unused inputs of the palm pad for a cheap security system (monitor those in Homeseer so if these signals are received while your security system is armed, send an alarm signal in your home).

These circuits do take some time to build. If there is a large demand maybe circuit boards could be constructed. Of course this would take someone laying out the boards and getting them made (not cheap, I believe this would cost over $35 per board). Of course you would still have to solder the components onto this board, but the assembly time would be drastically reduced. I did notice THIS thread on making circuit boards over at the Homeseer forums.