@Crossroads

The limit is a spoof on the 10 round limit to magazines in guns.  NY state just passed a law limiting guns to magazines of less than 10 rounds.

Maybe they don't want you to mistake misuse it for toilet paper!

I just left my motion sensor in-circuit and soldered a wire to the appropriate terminal on the opamp output.  It was easier for me to use their circuit rather than redesign the whole circuit.  As long as you know the proper input voltage, you can use their circuit and repurpose the motion sensor for yourself.  Once you've done some experimenting, you can buy one from radio shack or online for around $10 US.  Sounds like you're on the right track.  Have fun.

Most of those cameras can see infrared, so if you didn't want a light turning on to bother you when you're trying to go to sleep, you could use an IR LED as the light source.  May need to check that it will properly illuminate the target.  As Nick said, you could just turn it on intermittently, so you don't use too much power.

So I'm wondering if you've had any luck with your project.  Have you been able to locate the output pin from the final stage of the amplifier?  Hopefully, you're on your way to using this motion sensor for your own purpose.  I look forward to hearing about it.

Looks like you're not seeing any action from the community on this.  I have played with some motion sensors that I hacked from air fresheners.  I can't speak to the one that you're describing, but I can tell you that the LM339 is a quad op-amp.  It is used to amplify the output from the sensor up to 5VDC.  You should be able to verify this by finding the appropriate output pin on the op-amp with a volt meter.  You'll have to follow the circuit traces and do some detective work for this.  The output pin would pulse high for about a half-second when the sensor "sees" motion.  Just check each one until you find the one that outputs the highest voltage.  You could solder a wire to that circuit trace and feed it to an Arduino as an input for your new project.

LM339 datasheet can be found here: http://datasheetcatalog.com/datasheets_pdf/L/M/3/3/LM339.shtml

@TrailerTrash
If you're camping at an electric site, use electric heaters.  You're paying for it anyway, why use up all of your propane?  We use the 30 amp and plug one heater to a receptacle inside.  We run an extension cord to the 20 amp plug outside and bring it inside for the 2nd heater on really cold nights.  We have a Flagstaff popup camper and have camped down to 35 deg F and stayed very comfy.   Another idea is to use electric blankets at night.  Happy camping.  I do like your electronics ideas, by the way.  Looks like a fun project.  May I suggest using RGB LEDs for some mood lighting?

I think it's a testimony to the ferocity with which we are faced when demanding that information be free to all.  The powers that be are not friendly to many freedoms, especially the freedom of information.

I built a "smart" night light with an ATtiny85 and a motion sensor hacked from an air freshener.  It is normally PWM LED at a dim level.  If it "sees" you, it goes full bright.  After 30 seconds of not "seeing" anyone, it goes to a dim level again.

Are you controlling the temperature for a single part of the space or are you truly zoning the system using dampers in the ductork?  Is this a ducted system?

I think they look pretty good.  I'm one of those stubborn people who has to do everything himself.  You know, save some money and spend twice the time.  I'm a mechanical engineer by trade, so I guess it comes with the territory.  I've looked into the printerbot, I think when it was on Kickstarter.  They look like nice machines and seem to be well designed.  It depends on what size you're planning to get as to what I'd recommend.  The Jr. model looks to be a good price.  The Plus and LC models go for about the same as an assembled Prusa Mendel on Ebay.  Pick your poison, I guess.  I would do some checking around to see what kind of reviews people who have bought the Printrbot would give.  Don't get into a hurry and research well.  You'll be glad you did.  Have fun, that's the most important part, along with the learning.

Update on my machine:
I just got my smooth rods, bearings, belts, and pulleys today.  Only a few major parts left to get.  Electronics, hot end, and heated bed, plus nickel and dime stuff.  It's coming along nicely.

@wildbill

You have the whole kit and are only half-way?  My bottle neck is money.  I'm trying not to spend too much at one time so that I stay out of trouble at home.  Mine is as complete as it can be right now without more parts, which will arrive tomorrow.  By the end of this weekend, I'll be back to waiting for the next parts order.

This is your official kick in the pants to get going on that thing 
I want to hear how it's going and see pictures!

http://www.reprap.org/

This is where I've found most of my information.  There is a forum there too.  I'm about 1/3 complete with a Prusa Mendel.  I've been buying some parts from my local hardware store--all thread and nuts, washers, etc.

HVAC zoning from a single system is a complicated animal.  You should have the product data for your equipment so you can determine the minimum allowable airflow for your system.  If you close too many dampers, your airflow goes down and the static pressure goes up.  If you're using a gas furnace, it can cause high temperature limit trips in heating.  In cooling, it can cause indoor coil freeze-up problems, and ultimately cause failure in your air conditioner.  Lack of airflow in a cooling system can prevent all of the refrigerant from being boiled off in the indoor coil (evaporator coil).  Since you can't compress a liquid, you have problems.

All of this being said, you should have a leaving air temperature sensor installed so you can take action to shut the system down before some of these things become problems for your system.  I can provide more information for you if you like.  Let me know.

Yeah, that's kind of what I figured...

Oh well, I'll try the other one.  There does seem to be a lot more information about them on the web.  Guess I should have done more research before buying.  Live and learn.