How far can a motion sensor detect

Thread Starter

Man10

Joined Jul 31, 2018
44
As long as you know there is human being there and would not know there is a human being there without the motion sensor, you detect a person
 

AlanBell

Joined Apr 5, 2021
1
As motion sensors have a limited range—anywhere from 50 to 80 feet—you'll want to place several around your home, especially in areas where people frequently walk, such as hallways, staircases, living rooms, and bedrooms.
ACES ETM
 

Thread Starter

Man10

Joined Jul 31, 2018
44
As motion sensors have a limited range—anywhere from 50 to 80 feet—you'll want to place several around your home, especially in areas where people frequently walk, such as hallways, staircases, living rooms, and bedrooms.
ACES ETM
So motion sensors can detect a human being that is 80 feet away?
 

Alec_t

Joined Sep 17, 2013
11,981
Do a bit of googling and check the specifications of commercially available motion sensors. They should state the range.
 

Yaakov

Joined Jan 27, 2019
2,358
So motion sensors can detect a human being that is 80 feet away?
Motion sensors cannot detect human beings, they can detect motion, variously of a heat source or a radio reflective object. Anything that is hot and moves, or reflects and moves will be detected. This is an important point unless the only thing that fits that description in the area it is observing is a human being.
 
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Yaakov

Joined Jan 27, 2019
2,358
@Yaakov beat me to it!

Seriously, if you definitively want to detect if its human the only solution is a camera and some machine vision/AI software. That works well.
One *could* detect motion with a PIR or RADAR sensor and then confirm it with image recognition, but I think the TS is expecting the detector to distinguish humans, hence my original question above, “does a big dog count as a person?”.

There are ways to mitigate false alarms in some cases, such as interior home PIR detectors aimed too high to be triggered by pets walking around, but at 80 feet I can’t think of anything like that which would make it work.

I think we need to know why the TS wants to do this to make any useful suggestions, or perhaps it is an area where there can only be people?
 

MrChips

Joined Oct 2, 2009
23,069
Depends on your definition of a motion sensor.
You can detect a human, moving or still, from a mile away.
You need to think outside the box.
 

dl324

Joined Mar 30, 2015
12,677
So motion sensors can detect a human being that is 80 feet away?
LiDAR has a range from 10cm to hundreds of meters. They use rotating mirrors to sweep the beam, so the number you'd need depends on the region you want to scan.

EDIT: And as others have mentioned, motion sensors just detect objects.
 
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Tonyr1084

Joined Sep 24, 2015
5,804
My sidewalk is about 30 feet from the front door. I have a motion detector porch light that in the winter will detect someone walking past the house. In summer it doesn't see them. It has a lot to do with heat differential. If it's 95 degrees out and someone walks by with a similar body temperature it doesn't detect the motion. In summer time cars sometimes trigger the light but in winter it goes on every time a car drives by. And I think I have it set to either low or medium sensitivity.

One thing you can do to defeat a motion detector is to walk straight at it. Eventually it may see you, but if you move across the field it will detect you fairly quickly. Even if you move slowly.
 

Yaakov

Joined Jan 27, 2019
2,358
One thing you can do to defeat a motion detector is to walk straight at it. Eventually it may see you, but if you move across the field it will detect you fairly quickly. Even if you move slowly.
Yes, this is because of how the PIR sensors work. They depend on changes that have to do with lateral movement and the odd looking IR lenses on them are designed to maximize that.
 

Thread Starter

Man10

Joined Jul 31, 2018
44
I started this thread, because I am hoping to build a certain device. If i set up a camp in wilderness, the device can detect motion ideally 80 feet away, giving me advance warning something is coming. I thought you might know of any model that detects motion 80 feet away. Just trying to learn how to build such a device.
 

Reloadron

Joined Jan 15, 2015
5,876
You can pretty much have whatever you want. It's not a matter if it can be done but what it cost. Wilderness implies limited field of view in any direction, things like trees and brush? Sensors have a field of view so if you want 360 degrees coverage you need more that one and you need an unobstructed view. You can have whatever you want if you have deep enough pockets.

Ron
 
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