Let's Make Robots!

PIR (Passive Infrared Sensor)

Vendor's Description: 

PIR's are cheap little things that combined with a little chip (PIR Sensor Control IC) and possible a Fresnel Lens will tell you if there is motion in font of it. Especially that of a human body, as it is reacting on Infra Red.

You can not use a PIR for anything but on something that stands still, to detect something else that moves.

No, you cannot use a PIR to make a robot follow you. The PIR only detects changes. A moving robot (even turning it's head) would be one constant "alarm" of "changes" - not possible to tell what is what.

If you want to make a robot follow you, you either have to use a camera and some serious calculations, or something like the devantech Thermopile array sensors or hack an Infrared thermometer (often refered to as a Laser thermometer asthey often come with a guiding laser-beam).. or something else :D

PIR's can only detect changes! A moving robot will detect changes all the time! 


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But it really is impossible to help you with the info that you (don't) provide.

here is what it looks like pir,hmmm didnt work, oh well .my image didnt work ,its on a site called futurlec


Nice postings. Not.

hay i got one of those with the lens already on it but i dont know which pin is for what!(there are 4 pins)

can anyone help?

Have a look at the datasheet for the PIR you bought.


I bought two of them from Goldmine Electronics.  I am not sure if they are as good as the ones you all are buying but I had bought them thinking I might be able to use them for tracking similar to IR Emitters and Receivers but without the Emitter.  Anyway,  I am just now starting to mess around with them.

They have three leads.  I have no docs on them (probably thats why they were 99cents).  Any help on V+, ground, and signal would be great.  Mine are flat see the link for a picture.  I know you won't be able to tell me without having one but any help in discovering which is which would be great.  And please keep it simple I am a beginner.


You can buy them from All Electronics for $3.95. Not too bad, but more then $2.



Hey guys!  I notice it's been a while since you've been talking about this, but I was wondering if anyone knows how to buy these passive infrared sensors under $2.  I only need a range of a few inches, actually, so I figure there's gotta be someone out there that makes these weak ones for a smaller price.


Let me know!  Thank you very much

I made a lot of changes to make this thing work better. First the major change. AUTOCALIBRATION! Yay!! No more messing with potentiometers. The sensor simply looks away and adjusts. I have never tried this but in my dispair for a DAC I made a simple one with a PWM signal and a RC filter. There were also some tracking fixes that made it better. Check out the video!


Tomarrow I will pick up a larger resistor to incerase the gain of the opamp. I am using a little over 1mega ohm now. Going for 10M ohm. The sensor now can see me standing at about 2-3 feet. I hope with more gain I can increase the range. Next video will be it tracking me!


Exciting! :)