user11815: I'm looking to build a motion sensor which detects if an object is in the monitored area. Doing some researched I found out that I can use PIR motion sensor for this but it seems the area it monitors is pretty small. 
I need something that can monitor about 3 feet x 1 feet area. Is there something else that I can use for this?
My goal is to light up some LED lights when an object is detected in that area. 
Thanks in advance.

user4519: A standard PIR motion sensor will work fine.  It can monitor motion in a very room.  You just need to make sure the PIR sensor is far enough away.
Here is one article that states it should work up to 10 meters away.
https://www.mobotix.com/eng_US/Support/FAQ/Configuration2/What-is-the-range-of-the-PIR-Passive-Infrared-motion-detector
Note that the device that the PIR sensor is mounted on must be stationary.  It will not work on a robot of anything that is moving.

11815: <p>I'm looking to build a motion sensor which detects if an object is in the monitored area. Doing some researched I found out that I can use <a href="http://www.adafruit.com/products/189?&amp;main_page=product_info&amp;cPath=35&amp;products_id=189" rel="nofollow">PIR motion sensor</a> for this but it seems the area it monitors is pretty small. </p>

<p>I need something that can monitor about 3 feet x 1 feet area. Is there something else that I can use for this?</p>

<p>My goal is to light up some LED lights when an object is detected in that area. </p>

<p>Thanks in advance.</p>
 4519: <p>A standard PIR motion sensor will work fine.  It can monitor motion in a very room.  You just need to make sure the PIR sensor is far enough away.</p>

<p>Here is one article that states it should work up to 10 meters away.</p>

<p><a href="https://www.mobotix.com/eng_US/Support/FAQ/Configuration2/What-is-the-range-of-the-PIR-Passive-Infrared-motion-detector" rel="nofollow">https://www.mobotix.com/eng_US/Support/FAQ/Configuration2/What-is-the-range-of-the-PIR-Passive-Infrared-motion-detector</a></p>

<p>Note that the device that the PIR sensor is mounted on must be stationary.  It will not work on a robot of anything that is moving.</p>
