Suggestions for distance detect HW - Page 1
Forum section: electronics / projects

author: jcosper
author_rank: Contributor
timestamp: September 17, 2016, 05:41:48 pm
content: Hi all,I am working on a project where I would like to detect motion in 360 degrees from ~0' up to ~15' (~5m). My first thought was to repurpose some PIR sensors into a 360 array. Any other cheap suggestions?Thanks in advance!

author: DaJMasta
author_rank: Super Contributor
timestamp: September 17, 2016, 06:14:03 pm
content: To get full 360 on a lot of things you need motion components, or you need optics and processing power, so I think PIR is probably a good bet. You can actually get the sensor under a lens pretty cheap if you don't want to rip something apart to get one, but if you have a candidate ready for surgery, by all means have at it.I guess if you can setup the area you are scanning in, there are probably more options - but PIR sounds like a simple and cheap option.

author: jcosper
author_rank: Contributor
timestamp: September 17, 2016, 07:19:24 pm
content: Yes I would be scanning radially, so the scanning source would be at the center of the circle.

author: bitslice
author_rank: Frequent Contributor
timestamp: September 17, 2016, 07:31:53 pm
content: So that's two 180 degree PIR's back to back,or is there a need for more granularity here?you said distance..?

author: nctnico
author_rank: Super Contributor
timestamp: September 17, 2016, 07:57:37 pm
content: One PIR sensor with a lense should do it but it gives no idea on how much motion is detected and where. More sophisticated would be to use a camera + fish eye lense and image processing software.

author: SeanB
author_rank: Super Contributor
timestamp: September 17, 2016, 08:21:13 pm
content: Use a few narrow beam ( around 45 degrees for the most common narrow beam ones) arranged in a circle, with a second circle at a slight angular offset to improve sensing of slow moving warm objects. 16 sensors is a lot, but will at least allow you to filter out spurious responses somewhat, simply by using coincidence detection to see if 2 or more sensors covering a single sector have triggered, which reduces the false triggering that you might get.

author: jcosper
author_rank: Contributor
timestamp: September 17, 2016, 09:23:20 pm
content: Has anyone had any good luck with some purchased PIR sensors in an application? Preferably cheap ones. Sparkfun choices look pretty weak, but Digikey has a wide selection.

author: bitslice
author_rank: Frequent Contributor
timestamp: September 17, 2016, 09:37:05 pm
content: At a certain point you may as well pull the trigger on a Lidar/rotating mirror setup,at least then you've gained a massive amount of functionality.What's the project anyway?

author: Muttley Snickers
author_rank: Unknown
timestamp: September 17, 2016, 11:23:14 pm
content: We use either the Takex (Pulnix) or the Optex sensors and they are both extremely good and recognised brands, there are numerous others around such a Bosch, Crow, Aleph and so on, we also use these depending upon the application and environment.If your application involves measuring the distance to a target then these PIRs won't provide that, they will only trigger the onboard relay when movement is detected within the designated range of the sensor.Takex PA-6810E.http://takex.com/pa-6810e-pr-1825.phpOptex SX-360Z.http://www.optexamerica.com/security-products/sx-360zOptex FX-360http://www.optexamerica.com/security-products/fx-360

author: jcosper
author_rank: Contributor
timestamp: September 19, 2016, 02:50:52 pm
content: For this application, it doesn't need to be highly sensitive or accurate. I was planning on butchering some motion flood lights from the local thrift store. Just curious if there might have been a better way. Thanks for the suggestions.

author: Pack34
author_rank: Frequent Contributor
timestamp: September 19, 2016, 03:49:41 pm
content: What's your working distance and size limitations? You could always use an IR sensor and then rotating optics to change the direction.

author: hillflyer
author_rank: Contributor
timestamp: September 19, 2016, 09:23:40 pm
content: How about combining the PIR setup with a couple of ultrasound sensors?They might pick up stuff that the PIRs are missing...

author: deon
author_rank: Newbie
timestamp: September 20, 2016, 05:27:11 am
content: You could always go radar.Something like this:https://www.aliexpress.com/item/5-8GHZ-Microwave-Radar-Module-Smart-Sensoring-Switch-6-9M-Home-Control/32602485648.html

author: Pack34
author_rank: Frequent Contributor
timestamp: September 20, 2016, 02:40:58 pm
content: You could always just use a small array of IR and sonar range finders. They can all be analog and easy to integrate.IR would be great for edge detection and the right maxbotix sonars would work well for spread. It may be wise to trigger the sonars in a pattern to prevent unwanted reflections.