5 Pack HC-SR501 Pir Motion IR Sensor Body Module Infrared for Arduino

Hooked the VCC and ground to a 12v A/C adapter and it worked perfect. The 3.3v "trigger" pin (the "OUT") even had enough juice to directly power a red LED (tho a little dimmer than normal). Very wide sensitivity pattern. Tho description says "< 100 degrees" I thought it was greater than 120. At default sensitivity it would trigger easily from 8-10' away. I never adjusted it as that was the perfect distance for my needs. Holding it with the sensor "dome" facing down and the adjusting (orange) "screws" facing you, the left one is the sensitivity, the right is the duration that the OUT pin will stay "on" (i.e. hold at 3.3v). Minimum seems to be around 4 seconds.

I first bought a pre-built 'smart' light switch with a motion sensor that was WAY too sensitive and couldn't be adjusted. I decided to go the DIY route and bought these. I connected one to a NodeMCU, which I set up with Home Assistant using MQTT (along with a simple 'smart' switch sans motion sensor). It's awesome, gives me so much more control and cheaper. I do get some false-positives, but not nearly as much as with the pre-built unit. I suspect it's due to being in the garage and the sensor picking up sunlight/shadows coming in through cracks in the garage door. Overall, very happy with the purchase.

Bought these for Halloween decoration triggering. They work well, but the overall design has it's limitations (doesn't matter what MFG). Super sensitive to ambient light, so works well in a darker/indirect light situation. Also only really sensitive in 1 plane/movement direction. So you may have to rotate it 90* as it's not a cone of sensitivity, more like a long oval in one plane.

These are great for turning the screen off and on, in my controller box.

I left 5 stars because this listing for the HR-505 was truthful and said 4.5V as the minimum operating voltage. Many other listings say 3.3 to 12V. These are useless for that and cost me a couple days before I gave up. You need the AM312 for 3.3V usage.

I'm providing a middle rating because documentation is not good. I don't know if I misread the specs when I purchased but I thought these PIR sensors would work with 3.3v input/source voltage and output 0v low and 3.3v High on output. I now know that they certainly need 5v source input voltage and output 3.3v. When I provided 3.3v input power they acted erratically and would not go predictably low. Using 5v input the 3.3v output consistently dropped low to 0v. In Summary: 5v In = consistent 3.3v out when triggered, and 0v when clear/not triggered.

This product is perfect, and I love that it has a delay. I can wire this up to a board as-is without building a delay circuit myself. I've been using one continuously for a few weeks, and it's very responsive with a nice range. It has pretty good depth, but I haven't tried to press it. It can spot motion across an entire (average) room easily. I have projects lined up for the other ones included in this pack, and if I need more, this is where I'll get them.

According to specs, these PIRs should be identical to others we’ve bought on Amazon, but upon validation we discovered that they have an inconsistent (and possibly oscillatory) “desensitization” period between the HIGH state trigger and the return to LOW state. Turns out, they’re missing a capacitor that’s crucial for consistent timing, rendering them useless for timescale measures. I’ve included a picture of the missing capacitor as well as a picture of a fully functioning device from another Amazon seller. What’s worse is that this is not just a simple error — they seem to have been intentionally snipped! The seller likely received complaints about latency, and this was their fix. You can see the same modification in other customers’ (positive) review images. To be clear, this product is defective. Amazon needs to take action.