Detect something near you.

I'm sure there is a word or acronym for what I am after. I know there's radar, I know ther's lidar, I know there's passive IR detection.... but I'm sure there's something else....

Let's say there's a car, and I want to turn the lights on if something (person, cart, dog, bird) breaks a 1 meter personal-space sphere.

So the car parks, and there's a parking meter & a tree with in range, but once it's parked, is there a way to detect something has come close to it?

I recall reading something that used radio waves in a non-radar like way. Sort of sensing a change in antenna attenuation...

Just trying to get where I need to read so I can learn how to do it.

I would think there are too many variables for a simple detector. You would need multiple sensors for metals, people, animals etc, then a means of range finding.

Weedpharma

What about an ultrasonic "sonar" sensor such as are used for parking sensors. They are easily operated with an Arduino and can measure distance.

Passive Infra Red could be used for animals (including people) but I don't think it's possible to specify a distance.

...R

The phrase you're looking for is, "proximity detector".

http://www.ebay.com.au/itm/4-Car-Rear-View-Parking-Sensor-Reverse-Reversing-Radar-LED-Buzzer-Alarm-System-/201369342792?hash=item2ee28c5348

What about this?
Setting sensitivity might be a problem as you cannot be near car to do so. Maybe a few seconds after doors locked the system takes a reading and uses that as it's baseline for sensitivity.

thank you all! Now that I know what to search for I should be ok.
I recall reading an article about reading a radio signal; and when something got close to it; the signal would change -- sort of like a theramin.
My idea is to have a light on the dash of my motorcycle; when it's on, there's something close to me, anywhere -- ie: Don't change lanes or hit the brakes. Sometimes, even with turning the head, there are blind spots due to helmet & riding gear. and then as an alarm (less sensitive version) for when it's parked, if someone gets right up on it; to turn the lights on / honk the horn, something quick to let them know "stop backing up, you're going to hit me" (The later part of this just happened to me in my apartment because someone backed up and 'didn't see me' and toppled my bike...

Thanks! I should be good to go for now.

My idea is to have a light on the dash of my motorcycle; when it's on, there's something close to me, anywhere -- ie: Don't change lanes or hit the brakes. Sometimes, even with turning the head, there are blind spots due to helmet & riding gear. and then as an alarm (less sensitive version) for when it's parked, . . .

A proximity detector as a part of an alarm system for a parked motorcycle probably has merit.

Using a simple proximity detector as a warning system while the bike is in motion strikes me as a really bad idea, a distraction without any meaningful up side.

I'm not so sure about a "distraction" -- no more distracting than the high beam indicator, and less distracting than the turn signal indicator.
it's not meant as a replacement for looking, turning your head, using your mirrors, but rather as a double check "you might want to check again, I sense something" -- of course it will not be perfect -- riding the inside lane against the barrier will always show 'something is there'; but I've seen lots of motorcycles change lanes nearly hitting the drivers door because they were in a blind spot...

The primary reason tho is to say "HEY!, don't back up anymore"; the 'check again before changing lanes' is an after thought of something that might be useful.
Not all ideas are universally appealing. I wear reflective SOLAS tape on my helmet & down the frame of my bike -- I want to be as visible as possible, not "stealthy" like so many, with hidden plates, or dimmed brake lights.... Some see the solas tape as ugly, I say I like ugly if someone sees me because of it.

One problem with technology is that humans become complacent and dependent upon it to be doing things it might not be intended, or capable, to do. I hate the idea of a lane change warning system and the idea of depending upon a homebrew version, particularly on a bike, seems suicidal to me. But, I like the proximity alarm idea for a parked vehicle.

re "distracting" My thinking is that 1) A light on the dashboard isn't going to do any good if one is not looking at it, 2) If one is looking at the dashboard while lane changing or other traffic maneuver, they are in my view, distracted from looking somewhere more appropriate. In any case getting any meaningful sensitivity out of such a system is likely to result in a very high "false alarm" rate in a moving vehicle.

re "visibility" I ride in a hi-viz Aerostich "commute suit" which a friend calls the yellow highlighter outfit, though it's a bit muted from dirt accumulated over many years of use. It's hideously unfashionable, but a bit of extra insurance.

Was he a jerk for having the alarm, or a jerk with an alarm?
I do not like 'talking' alarms, or alarms with sirens -- people just ignore them -- that's why I just want a quick beep & lights flash - nothing too annoying for others, and a simple reminder of something there for someone who's parking.

Motorcycles (and/or riders) get crapped on all the time -- I have been yelled at for 'making a spot' next to a shopping-cart corral (where you return the cart in a parking lot); and also yelled at for 'taking up a whole spot' when I could have made a spot.... So anything on a bike that is too annoying is bound to just get you f'd with...