Asked — Edited

Hc-Sr501 Human Sensor Module Pyroelectric Infrared Module

Hi All,

I purchased a few of these PIR sensors on ebail for $4.50 (USD) each. They took a while to arrive from you all know where but they seem pretty cool. I am planning to add them to my sentry robot project at some point. I bench tested them and they seem too work just fine off the EZB using a single Digital port. +VCC, GND, signal. device trips high when motion is detected.

Pyroelectric Infrared Module (PIR)


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United Kingdom

Hi kkeast,

I ordered some of the mini PIR module

These are so small with only a 10mm hole required! I bought it because I wanted to make a Portal 2 turret, along with the laser modules

mini laser module

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That is an awesome idea! Portal 2 is the best! Love the laser modules could put three of them in a triangle to make it kinda like the Predator laser sight!

I may get some to do just that...great find!


I'm on eBay now and that's got to be a typo, right? 10mm = 1 cm. How the heck can you solder the wires to something that small?

United Kingdom

No, its not a typo. They really are small:D

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Wow! That's awesome. Thanks for the photo.


Hello guys,

I picked up this sensor at radio shack, 10 bucks.....bigger than the one you have but comes with the 3 pin connector...


Hey guys one more question. We are all using these sensors to sense humans not objects. For instance I'm putting one of these sensors on each side of my wall e. So when I move my hand I can make his head turn towards me and the his body.

I want to make sure these sensors are not for object detection.


United Kingdom

Hi hoolagen1,

These detect heat and movement, P.I.R. (Passive Infra Red), so they will only work when you move your hand in front of them, if you keep your hand still they will not detect it, you would need an A.I.R (Active Infra Red) which monitor the area and activate when there is a change in the environment.

Hope this helps:D




i love it! its PIR great news cuz.

I also want to add sound sensors next to the PIR sensor.

But i was wondering if that would be dumb because the PIR sensor would always go off....making the sound sensor useless....

but now that i know what a PIR vs AIR is, this will work!

thanks for the new wrinkle in my brain.


PIR works by detecting heat source not sound and it doesnt make any sound so it wont set off a sound sensor

i am looking to get a PIR but analog output to measure person distance to camera found one at digikey AMN22111 $15 LOOKING LOWER COST ITEM ,but specs are good

now on the mini PIR looks good for another project also


What port do I connect PIR sensor to? Adc or a Digital? Link to buy? Thanks.


The ones i bought (link above at first post) connect to Digital. The ones Djandco posted above also should connect to digital. They both register logic high or low for outputs (high when motion detected). Sounds like robotmaker is looking at something different to determine distance. I just wanted motion detection.


analog port for the one from digikey digital is great for detecting in a person comes in range of the sensor,like kind used for turning on night lights ,alarms,light switch ,mostly high with in range when not low

on analog it detects the person and how far away from sensor,best one on the market is TPA81 THERMAL ARRAY THAT HAS 8 PIR in array and builds of a thermal image and compares to room has IC2 output on digikey sensor it has analog voltage

digital PIR also has analog circuit,then has a comparator ,that has a digital output and most have a set pot for range ,ALSO SOME HAS A SPECIAL CONE FOR to focus a wide detection area

another one used alot is ELTEC 442-3 PIR sensor analog output there are a few others,but thses are the ones mainly used a lot there some 3 pin analog used in some toys,like R2-D2 INTERACTIVE ROBOT uses and maybe the same one used in MINI PIR detector with digital output

one posted by KKEAST looks like ELTEC 442-3 PIR,i have that one plus ELTEC 442-3 ,AND my favorate one TPA81 plus the one from R2-D2 that looks like the second link by Djandco,havent bought that one yet,but will get some .like the small size i mostly work with every type of sensor and buy different ones to test them out,they have good points and bad points for toy robots we hack ,think best is small size,low current .low cost


@jstarne some digital PIR'S ,can hook up to analog by finding the input to comparator circuit or one of the pins of PIR SENSOR ,they have 5v ,gnd ,output ,but not the board connections ,it has digital pin,5v and gnd and can tell the distance from person to the robot ,like SONAR or IR can when i try to add sensors to my robots i make,i make the hole as small as i can or hide it