So, I'm hunting for ideas for a reliable vehicle passenger sensor technology that doesn't take much power and can handle interior temperatures. It must be able to detect a passenger who is unbelted, in any position, and potentially unconscious. Thoughts?-- RayfordSteele, Aug 22 2012 Does Self-Awareness Require a Complex Brain? http://blogs.scient...re-a-complex-brain/Popped up on [Dub]'s RSS hose, today [Dub, Aug 23 2012] The vast majority of modern vehicles (US, at least) have a weight sensor in the front passenger seat, the effect of which can be seen by setting something heavy on the seat without buckling the seatbelt.-- MechE, Aug 22 2012 I'm aware of weight sensors. These are defeatable by sitting or standing in a pattern that the sensor pad doesn't recognize. They are for shutting off the passenger airbag and activating the belt buzzer. Not robust enough for my application.-- RayfordSteele, Aug 22 2012 Then you're going to be rather limited. Best bet would be an IR camera or similar. That's going to be the only thing that covers a large area completely, but it's not super low power, since you'll need some image processing capability as well.
If you don't need to differentiate between passengers and objects, then a light curtain might be useable, but those tend towards the expensive, and also not the lowest power option.
An inexpensive ultrasonic might work, although, again, it won't be at all possible for it to differentiate between people and objects.
Any of the above should be available in versions that can stand up to higher temperatures.-- MechE, Aug 22 2012 Wonder if an IR camera could be fooled by thermal ghosting...-- RayfordSteele, Aug 22 2012 a sound-sensor and a thumbtack.-- FlyingToaster, Aug 22 2012 That's why the image processing. You should be able to process out steady artifacts, and ID a body shape fairly easily. It might be defeatable by riding around under a mylar blanket, for instance, but other than, you can probably do pretty well.-- MechE, Aug 22 2012 Hire an unregistered immigrant at subsistence wages to operate a toggle switch as required?-- 8th of 7, Aug 22 2012 Monitor fluctuations in CO2 levels with appropriate algorithms for when you are using the vehicle?
It is difficult to fully understand the context of your requirement for such a sensor. Rescue apparatus for first responders? Detect the criminal hiding in the back seat while you're parked in a dark alley? To 'find yourself' after a big night out?-- AusCan531, Aug 22 2012 [RS], are you afflicted with teenagers?-- swimswim, Aug 23 2012 I think something akin to the autofocus device on most mid to high-end cameras would work. There are several different kinds of autofocus, including “active” sound and infrared light time-of-travel measuring, infrared light point triangulation, and “passive” optical image focusing – I’m not sure which would be best, but properly designed, I expect most or all could reliably recognize a human in any position, and distinguish between adults, children, bags, boxes, etc.-- CraigD, Aug 23 2012 Weight on wheels? (or a combination of several suggested ideas) Recalibrated whenever the fuel tank cover is open then closed or the trunk is opened and closed. Might require some clever hysteresis to account for passenger in seat when refueling (assumes you won't be carrying unconcious bodies in your trunk... ) Could they have something on their person (e.g. Bluetooth device?) {Starts becoming slightly concerned with [RS]'s application}-- Dub, Aug 23 2012 What about a Turing test? That would differentiate a sentient passenger on the front seat from, say, a heavy parcel. A small console mounted on the dashboard could be used to administer the Turing test. People who fail the Turing test arguably don't need the protection of seatbelts.hmm - that might not work for unconscious people. How about some sort of IR Doppler system which would detect blood flow beneath the skin? - then your unconscious victim would be detected but a warm, freshly-killed corpse wouldn't. I too am becoming worried why [Rayford] wants this functionality.-- hippo, Aug 23 2012 [Hippo], has brought us to a very interesting philosophical question. Is an unconscious person still a person?-- Dub, Aug 23 2012 No teenagers. Baby affliction.
This sensor relates to my earlier idea for passenger overheating protection. It's to roll the windows down, alert authorities, call a telematics provider, alert your phone app, etc. if there is a risk of someone or some thing overheating in a parked vehicle. It was in response to a news report of a child that died because their forgetful grandparents left him in the car at the mall, and of another story where a guy simply spaced it when he was supposed to drop his child off at daycare and went to work instead. I could see this happening in the groggy morning hours to someone regardless of how good a parent they are.-- RayfordSteele, Aug 23 2012 If you're trying to find a single remaining passenger, then an audio sensor might work. I suspect breathing or heartbeat might be distinct enough to be picked from background noise. It wouldn't be able to count a number, though.
A very finely tuned motion sensor might work to pick up breathing from an unconcious person, but I wouldn't count on that.
IR would get problematic around 98.6F.-- MechE, Aug 23 2012 // light curtain might be useable//
A simple low-power laser pointer and a photodiode would detect anything blocking the beam. You'd need at least two, or more if you have big armrests or want to detect someone on the floor.-- MaxwellBuchanan, Aug 23 2012 Heartbeat over exterior noise? Um... no.-- RayfordSteele, Aug 23 2012 random, halfbakery