Smart car sensing with RF

Posted May 12th 2008 10:27AM by Will O'Brien
Filed under: home entertainment hacks, home hacks, daily

In order to tell his home automation system that he's home, [Jim] mounted a RF transmitter in each of his cars. When the car is on, the transmitter is powered up. The house picks up the transmitter signal when the car arrives or departs. With that information, he was able to set up some stateful rules that can be activated when people arrive or depart. Some people prefer to use APRS and read vehicle location from the transmitted GPS coordinates, but this is a bit cheaper and doesn't transmit your position to the entire world all the time. The useful range is about 100 feet, so this can work even if you have to park in the street.

Reader Comments

(Page 1)

1. Done that. People that have Crestron home automation have enjoyed that kind of setup for at least 10 years now.

Posted at 2:45PM on May 12th 2008 by fartface

2. And they have been doing it at 200 times the cost of the Do it yourself'er

Posted at 4:13PM on May 12th 2008 by Wang191

3. I did this with Bluetooth. You can use the Linux HCI tools to scan for Bluetooth devices, and it will return a list of all the Bluetooth hardware addresses it finds. I referenced this output with a database of known Bluetooth hardware addresses, and set up a state machine using shell scripts to detect when a specific device entered or left range. The Bluetooth solution is good for situations where the location of someone's car doesn't necessarily dictate whether that person is home or not...I take my phone everywhere, but sometimes walk or bike places, or ride with someone else.

Posted at 5:14PM on May 12th 2008 by garrett

4. Wow this rocks. I really love this stuff. I'm going to look more into it.

Posted at 7:24PM on May 12th 2008 by DigitalMind

5. I've been using bluetooth for that as well. It can be very useful if you get a bit creative with shell scripts...
-My alarm clock only goes off if I'm at home
-As soon as me or any of my close friends or relatives arrive home, my P2P computer greets them and reads aloud a list of the files it has downloaded for them while they were out.

Posted at 6:47AM on May 13th 2008 by maddiyer

6. That's a really cool idea! Forget to turn the stove off? Lights?

No more!

If you were REALLY geeky, you could even create a forecast for when people "should" be home - then (assuming you have your AC system rigged up) you can create auto-profiles to maximize the efficiency of your AC...

And a host of other incredibly nifty things ;)

Posted at 3:56PM on May 13th 2008 by srilyk

7. So, other than #5 (the alarm clock thing sounds neat), what exactly is this good for? OK, my computer knows I came home (though I think voice recognition using an ambient mic would be cooler)... now what?

Posted at 11:55AM on May 14th 2008 by James

8. did my own with a cheap radio shack wireless security system. used the motion detector in my car. i did it to protect my 1966 mustang from theft along with the car alarm. this device will call my cellphone if my car is taken from where i live. not the most secure neighbor hood and this helps me feel better.

Posted at 9:37AM on May 20th 2008 by kevin mcguigan

Add your comments

Please keep your comments relevant to this blog entry: inappropriate or purely promotional comments may be removed. Email addresses are never displayed, but they are required to confirm your comments. To create a live link, simply type the URL (including http://) or email address and we will make it a live link for you. You can put up to 3 URLs in your comments. Line breaks and paragraphs are automatically converted — no need to use <p> or <br> tags.