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Driveway Probe with Insteon E-mail
Written by Peter   
Driveway Probe Home AutomationLooking for a way to receive notifications when a vehicle is on your driveway or nearby?  Motion-based systems regularly false alarm due to falling leaves or animals, however using a magnetic based system with an Insteon EZIO provides a flexible, reliable solution to getting an early warning - even on your mobile device.  What were the biggest challenges in this setup?  Read on to find out...

Time:Approximately 1 hour

-Magnetic-sensor based system (Dakota Alert DCPA-2500 used)
-22-18 AWG Female terminal connectors (x2)
-Solid or stranded 18 AWG wire
-Insteon EZIO (a 2x4 is shown in photos, however other models will work as well)
-Precision flathead screwdriver (for EZIO and Dakota set screws)

Background: We recently moved to an acreage where the driveway is fairly long and I have a desire to know when a vehicle is coming to our house so we're not surprised by an unexpected visitor.  During my research I learned that motion sensors were subject to false alarms from falling leaves and animals, while driveway probes relied on magnetic fields and as such were only affected by metal passing through the field, as would be the case with a car. 

After researching many, many driveway probes I found the Dakota Alert series (DCPA-2500) had generally positive reviews and offered a wireless transmitter and plug-in receiver configuration, which was ideal for my setup.  Armed with this, I ordered one and once received proceeded to experiment in my living room with the sensor.  The kit is comprised of a white sensor that looks like a PVC pipe and is just over a foot long, followed by a 50 foot cable which connects to a weatherproof black box where the logic board, batteries and transmitter are.  Separately, there is a receiver which plugs into the wall, has a volume knob, a few configuration buttons and a series of dry contacts for relay outputs.  One receiver can be used for up to 4 sending probes, and each can have a different chime and relay output.  I put the batteries in, plugged in the receiver and moved a pair of pliers across the sensor.  "Ding dong" came out of the receiver, and I figured I was all set!
Mobile iPhone Driveway sensor
Living in a colder climate, I got bundled up and placed the sensor in the foot of snow, running the sensor transmitter box to a nearby tree, as the manual states the transmitter should be 5 feet high to achieve the best range.  With everything in place I headed back to the house to connect the receiver to my home automation solution.  I'm using an Insteon EZIO 2x4 to detect the relay voltage and trigger events in Homeseer. 

I had originally tried locating the receiver in our basement, but the reception was basically non-existent (not surprising given the 300 foot distance from the receiver PLUS the underground, minimal window basement environment) so I moved it to the office which is on the side of the house closest to the transmitter and it works fairly consistently now.  When a vehicle is detected in our driveway, Homeseer runs a series of scripts:
• A non-queueing script to send a Growl event to our computers.  Growl is cross platform so our Macs can see the message sent by the Win 7 Homeseer server.
• The Growl notification also sends a Prowl event to our iPhones during daytime hours.  Prowl consists of a plugin module for Growl and an app for the iPhone that receives push notifications, and hour restrictions for alerts can be configured in the app.
• A script to turn on the TVs in the house, pause any currently playing media, and select the HDMI source for the CCTV feeds to show the security footage of whoever is approaching.  The CCTV system will automatically display all the camera feeds in a grid until motion is detected at which point that feed becomes the full-screen view, or if motion is on multiple feeds it rotates between them based on level of motion.  After 15 minutes the TVs turn off and the HDMI sources switch back to the media player source.  I will elaborate on this setup in a future article (or two - it might take two).
• A script which pulses all the interior lights of the house so an awareness of the upcoming vehicle is conveyed even if you aren't in front of a TV, iPhone or computer.

The solution has worked fairly well, however there were some struggles, and I would suggest there are opportunities for improvement still.  First, the struggles.  After initially setting up the probe, I tested it with success, only to have subsequent drive-by tests fail.  I experimented with range, new batteries, placement of the receiver, and the rheostat sensitivity dial inside the transmitter.  Despite a relatively scientific approach, I'm still not convinced I understand the change that made the system reliable.  My current settings are as follows:
• Changed from default codes to a random code to reduce interference, using the dip switches set on both receiver and transmitter.
• Increased the sensitivity to about 80% of maximum.
• Placed the probe parallel to the driveway and expanded the wire such that no coiled sections exist.
• Located the transmitter as high as I could conceivably reach without a ladder (about 7 feet up).Magnetic probe for driveway
• Changed the receiver from using the built-in 12V output and an optically isolated input on the EZIO to providing the source voltage of 5V from the EZIO through a relay on the receiver, which also triggers when a detection occurs. 
• Switched the X3 and X5 jumpers on the transmitter, to X3 = 2 seconds and X5 = 10 seconds.  The function of these aren't documented anywhere (online or otherwise) but I suspect based on testing that X3 is the minimum length the magnetic field must be disturbed to trigger a transmit, and X5 is the length of time the transmitter will transmit for. 

The majority of people seem to have success without these changes, however if you are experiencing issues, I would suggest trying some or all of them. 

Regarding improvements, currently the system will trigger when leaving the house as well as arriving, which triggers the scripts to send alerts, flash the lights and turn on the CCTV, all not particularly useful to let me know a guest was just here.  I've setup time restrictions so none of these take place during my 5am morning departure, but limiting guest departure times to predetermined windows may feel a bit draconian.  One solution is to use a second probe at a point further down the driveway and based on the sequence of triggering determine vehicle direction.  For vehicles within our household, the garage door can be connected to the EZIO such that a garage door trigger should preclude the events from firing for a time window long enough to leave the driveway (3 minutes perhaps).  Once a gate is in place, presumably the sensor would be located on the outside of the gate, such that a gate opening event should prevent the vehicle detection events from firing for a minute or so. 

Overall I would say I'm happy with the 95% success rate of the system now and have been impressed with the functioning in temperatures as cold as -25 C (-13 F) and 2+ feet of snow. 

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3.23 Copyright (C) 2007 Alain Georgette / Copyright (C) 2006 Frantisek Hliva. All rights reserved."