Mydogcooperisapita
Posts: 18
Joined: Thu Dec 26, 2019 4:18 am

Which sensor would be most appropriate in this application?

Thu Dec 26, 2019 4:42 am

Hello,
New here, I look forward to learning and helping when I can. I have a sensor related question.

Imagine you have a garden, 10 feet wide and 30 feet long. You want to detect if any large animal approaches the garden. You don’t care about a deer 50 yards away, but you want to know if they are within a 25 yard vicinity and closing it.

The issue I have is this: the projects I have seen use algorithms to detect a change in the video or pixel. With trees blowing and animals past 50 yards, this would set off a lot of false alarms. The SR501 sensor I purchased appears to only work once you’re within 10 feet.

What would you do? Should I go with radar, lidar, or some other method? Or should I just mount 4 SR501 sensors (one on each corner) and see if there is a way to make it only detect large animals at a specific range? This garden is also near a road, so I’d want it to ignore cars as well.

Thanks in advance!

deepo
Posts: 606
Joined: Sun Dec 30, 2018 8:36 pm
Location: Denmark

Re: Which sensor would be most appropriate in this application?

Thu Dec 26, 2019 9:07 pm

I don't think you'll find a simple solution to filtering out cars and leaves moving in the wind.
So how about an infrared trip wire system, i.e. infra red diodes and sensors?

/Mogens

JohnsUPS
Posts: 185
Joined: Fri Jul 06, 2018 2:13 am
Location: USA

Re: Which sensor would be most appropriate in this application?

Fri Dec 27, 2019 12:56 am

deepo wrote:
Thu Dec 26, 2019 9:07 pm
I don't think you'll find a simple solution to filtering out cars and leaves moving in the wind.
So how about an infrared trip wire system, i.e. infra red diodes and sensors?

/Mogens
I was also thinking about something along this line. What came to mind was an infrared diode (or perhaps a laser diode) pointed to reflectors at the corners of the garden. The beam would be reflected around the perimeter (the perimeter being as far away from the garden border as you wish), and back to a receiver. A break anywhere along the path (perimeter) would then do something. Downsides would be snow, rain or falling leaves though.

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Gavinmc42
Posts: 4657
Joined: Wed Aug 28, 2013 3:31 am

Re: Which sensor would be most appropriate in this application?

Fri Dec 27, 2019 2:24 am

I would have said this was hard until John posted his progress with Yolov3
https://www.raspberrypi.org/forums/view ... 3&t=259562
I have yet to get his speed, but I did get it to work slowly after just a few days/hours of messing about.

The model library it might/should have Deer if it has Bears.
And you will have to have IR illumination for night time.
Jbeale has a post where he shows how to strobe the IR spotlights to the camera frame rates.
This reduces the power and heating issues and allows much high power out of the IR LEDs for a short time.

There are some IR lasers now that could be very useful.
VCSEL arrays are getting popular with VR/AR/3D gadgets so we should see them soon in the hobby market.
VCSEL are very efficient light sources.
I'm dancing on Rainbows.
Raspberries are not Apples or Oranges

LTolledo
Posts: 3919
Joined: Sat Mar 17, 2018 7:29 am
Location: Anime Heartland

Re: Which sensor would be most appropriate in this application?

Fri Dec 27, 2019 3:27 am

how about an array of doppler radar plus PIR combo

both detect movement, using each unit's output into a detect algorithm in the RPi....

I've tested each, but have not made any algorithm using the combo's output, to weed out false positives...

hmmmm.... might try it out during the break... ;) .
"Don't come to me with 'issues' for I don't know how to deal with those
Come to me with 'problems' and I'll help you find solutions"

Some people be like:
"Help me! Am drowning! But dont you dare touch me nor come near me!"

deepo
Posts: 606
Joined: Sun Dec 30, 2018 8:36 pm
Location: Denmark

Re: Which sensor would be most appropriate in this application?

Fri Dec 27, 2019 10:34 pm

JohnsUPS wrote:
Fri Dec 27, 2019 12:56 am
deepo wrote:
Thu Dec 26, 2019 9:07 pm
I don't think you'll find a simple solution to filtering out cars and leaves moving in the wind.
So how about an infrared trip wire system, i.e. infra red diodes and sensors?

/Mogens
I was also thinking about something along this line. What came to mind was an infrared diode (or perhaps a laser diode) pointed to reflectors at the corners of the garden. The beam would be reflected around the perimeter (the perimeter being as far away from the garden border as you wish), and back to a receiver. A break anywhere along the path (perimeter) would then do something. Downsides would be snow, rain or falling leaves though.
The leaves and rain can be handled using a little software signal filtering.
Just like a debounce filter for electrical switches to remove contactor noise.

One is described on page 20 in this document:
https://my.eng.utah.edu/~cs5780/debouncing.pdf

/Mogens

Mydogcooperisapita
Posts: 18
Joined: Thu Dec 26, 2019 4:18 am

Re: Which sensor would be most appropriate in this application?

Sun Dec 29, 2019 6:34 pm

Thank you all for your advice. I never even thought/ considered a beam. I will look more into that.

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