In courts and Airports they have hand held scanners that can detect metal. How hard would it be to embedd a similar device in street furniture , powered by mains, that could also via an additional circuit transmit to a cell phone when metal is detected including its location?

 

Everyman on the street has sth in the pockets what will cause the alarm then - keys, watches, marriage rings, jeans buttons, phone, etc etc Very unhandy idea....

 

In my case a large metal rod which is holding my leg together

 

Since most street furniture is mainly metal, you would have the problem that either the furniture itself would trigger the device or else the furniture would act as a Faraday cage to prevent detection of any external metal.

 

In courts and Airports they have hand held scanners that can detect metal. How hard would it be to embedd a similar device in street furniture , powered by mains, that could also via an additional circuit transmit to a cell phone when metal is detected including its location?

It wouldn’t be hard at all, but as people have mentioned above, its utility would be dubious.

Do you have some clever use in mind for it?

 

It wouldn’t be hard at all, but as people have mentioned above, its utility would be dubious.

Do you have some clever use in mind for it?

I just was thinking about all these knive attacks any way electronically that could be used to lower the risk.

 

I just was thinking about all these knive attacks any way electronically that could be used to lower the risk.

That would require a knife detector, not a metal detector. That's not something I can imagine how you'd manage.

Metal detectors would constantly trigger because of all sorts of other metal objects indistinguishable from knifes based only on the metal content.

 

Could some sort of radio wave at a certain frequency be absorbed by metal and this absorbsion detected by another sensor?

 

Could some sort of radio wave at a certain frequency be absorbed by metal and this absorbsion detected by another sensor?

The problem is how to decide if the metal is a knife. Detecting metal isn't a problem at all.

 

this clever team of boffins seem to be developing a useful radar microwave sensor detector.

 

That's not applicable to your use case.

It's very similar to airport body scanners, it's not a metal detector per se, and it can't be used for general surveillance as you would like.

 

Needs to detect tea cups and can openers too:

 

Steel cap-toed work shoes. Metal foil in a cigarette pack. Iron/steel belt buckles. Some metal body piercings. Just a few of the things that will set off a metal detector. Gold tooth crowns, silver amalgam tooth fillings, stainless steel or titanium surgical hardware, solid gold and silver jewelry, and ceramic knives will all pass undetected. Before they made us take our shoes off, I got dinged at the airport because the dress shoes I had on were steel capped safety shoes. I never even thought about it until the first time I got flagged going through the airport screening detector.

 

Would be set off by a lot as others have mentioned. Would give far too many false positives for the results to be used to as any evidence of knife carrying but could in principle be done.

 

There are also those of us who would never harm others unless attacked. The intrinsic flaw in all such schemes is that they would tend to disarm the law abiding folks and only annoy the law breakers. And I have heard from a quite reliable source that most crimes are committed by lawbreakers, and not by law-abiding folks. So the logical extension of that thinking would put a law enforcement on the street about every ten feet, which quite probably would reduce a lot of criminal activity. But I do see some challenges in that approach. And until it happens I choose to be equipped to protect myself until such time as a law enforcement person may arrive. Of course the attacker may be slightly injured. My thinking is that I am responsible for assuring my own safety and that if somebody else is able to assist then that is my good fortune indeed.

 

And there are those of us who have carried a knife in their pocket since the 1st grade in school. I never cut anyone other than myself or carved my name into anything. I have carved toothpicks, cut string and rope, played mumbleypeg, opened countless letters and packages, tightened screws, opened cans, put holes in leather and such. I've also been known to peaceably go about my business in town wearing a holstered sidearm as is my legal right to do so.

 

As Tech-People, it's easy for us to reach for a technology solution, but this ultimately leads to a very dark place.

We need to ask bigger questions, like why are more people driven to hurt others these days?
This is what needs closer examination.

 

Very true Sensa.. going back to the detection of knives my university has just received funding to develop a smartphone app for police to specifically detect knives made of any material: https://www.lboro.ac.uk/news-events/news/2019/april/government-funding-for-knife-scanner-tech/

Think it would need to be manned though so would be difficult to cover all the street furniture!

 

What's relationship between street furniture and knife?

 

Very true Sensa.. going back to the detection of knives my university has just received funding to develop a smartphone app for police to specifically detect knives made of any material: https://www.lboro.ac.uk/news-events/news/2019/april/government-funding-for-knife-scanner-tech/

Think it would need to be manned though so would be difficult to cover all the street furniture!

Ugh! this will just give the already jumpy cops a reason to harass people for having foil gum wrappers in their pockets.
I do not approve, it's that same misguided thinking that there is a tech solution to every one of society's problems.
It all leads to totalitarianism.