Help with PIR sensor interfacing

Hi

I am trying to interface two PIR sensors using PIC16F877A. The problem is the PIR 's output is not stable(o/p goes high after some fixed intervals of time) and the output remains high for about 6 seconds.

Do PIR sensors detect only human movement? From my experience it doesn't seem so. Please suggest a way to solve this problem.

PS: I am working on a project which is a Human tracking fan prototype. Two PIR sensors and a stepper motor are being used to track a person and rotate the motor so that the fan always cools the person.

Your Project seems quiet interesting. but for further work into it you should share some sensor part number or datasheet link

I am sorry but I myself don't have the datasheet. I bought from here https://probots.co.in/index.php?main_page=product_info&cPath=9&products_id=180&zenid=82061c7b4be19bddb62664950895cb22

I Haven't used this one but i have read something about his. following things i have noticed...
1. Each PIR has 2 sensors (like two eyes)
2. These sensors receive IR radiations from different sources (it may be human body or else) and Compare it with each other. If there exists some difference between readings of the two sensors that means there has been some movement, otherwise no.
3. Each sensor has got some settling time. (in your case its 6 seconds, with a range of 6 meters in front of the lens

generally in other sensors this settling time can be changed by use of some RC network.

Try keeping the sensor in a place where there's exactly no movement within a range of 6 meters and then see whether the pin still goes high or not.
Oh i forgot to tell you that the pin high low can be checked remotely by help of a led connected to Output pin of your sensor.