Author Topic: EEVblog #1287 - Gatekeeper Shopping Trolley Lock Investigated  (Read 1834 times)

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Offline texaspyro

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Re: EEVblog #1287 - Gatekeeper Shopping Trolley Lock Investigated
« Reply #25 on: February 27, 2020, 01:16:55 am »
Thats what I had always assumed, it was a simpler mechanical brake. But then, wouldn't that area get filled with ferrous debris?

I seem to remember that they collected bottle caps and nails.   Nails spread across parking lot exits are not a good thing.
 
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Offline amyk

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Re: EEVblog #1287 - Gatekeeper Shopping Trolley Lock Investigated
« Reply #26 on: February 27, 2020, 02:37:52 am »
I wonder if you can open them with heat.
If you don't care about them surviving, yes...
 

Online magic

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Re: EEVblog #1287 - Gatekeeper Shopping Trolley Lock Investigated
« Reply #27 on: February 27, 2020, 07:29:16 am »
Dave: your recording shows an 8 bit code. That code is probably store-specific and doesn't match the wheel you were sent. So maybe try all 256 possible codes?

That was my thought too, but frankly, what would be the purpose of each store having a different code? Is there really a need for carts stolen from supermarket A to be able to enter or leave the parking lot of supermarket B? The bit pattern may just be to protect from accidental triggering by noise.

If I wanted to lock this wheel, I would start with taking it to the supermarket instead of going there with a recorder and trying to reply the signal with speaker coils.
 

Offline mikeselectricstuff

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Re: EEVblog #1287 - Gatekeeper Shopping Trolley Lock Investigated
« Reply #28 on: February 27, 2020, 08:18:30 am »
My guess is that the code is to avoid false trips, and allow a handheld device to be used to reset them using a different code
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Offline HwAoRrDk

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Re: EEVblog #1287 - Gatekeeper Shopping Trolley Lock Investigated
« Reply #29 on: February 27, 2020, 11:28:48 am »
The local super markets around here just put knobbly paving at all points of access which makes it extremely hard to push the trolleys any further as the wheels jam and jitter on the knobbly surface cars can drive over it and people can walk on it but the spacing is just right to catch shopping trolley wheels which don't require expensive braking systems or buried coils.

When a new Sainsburys store was built in my hometown in the mid 90s, they put in a system that was a slightly more sophisticated version of this. The trolley wheels didn't have the usual rubber tyre, but instead had two radial flanges as the rolling surface. At all the pedestrian exits, they installed metal plates on the ground that had a longitudinal ribbed pattern, but the ribbing was offset every 6 inches or so, like this:

| | | |
 | | |


This meant it was impossible to push a trolley across, as the wheels would get jammed.

Ingenious, but ultimately didn't work too well, as people just carried the trollies the few feet, or wheeled them through the adjacent patchily-shrubbed areas. :)

The supermarket moved to a locking chain and coin deposit system a few years later.
 

Offline jancelot

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Re: EEVblog #1287 - Gatekeeper Shopping Trolley Lock Investigated
« Reply #30 on: February 27, 2020, 08:53:35 pm »
That in-wheel mechanism is supposed to prevent a trolley/cart from being stolen just locking one wheel? Hilarious nonetheless.
 

Offline jancelot

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Re: EEVblog #1287 - Gatekeeper Shopping Trolley Lock Investigated
« Reply #31 on: February 27, 2020, 08:54:46 pm »
Does that actually trigger any alarm in the shopping center once you reach out of the perimeter?
 

Offline thm_w

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Re: EEVblog #1287 - Gatekeeper Shopping Trolley Lock Investigated
« Reply #32 on: February 27, 2020, 09:34:14 pm »
That in-wheel mechanism is supposed to prevent a trolley/cart from being stolen just locking one wheel? Hilarious nonetheless.

Makes it slightly inconvenient, enough to dissuade most people. Same idea with the dollar coin, is a cart worth more than $1? Yeah, but $1 is enough to make most people think twice.

Does that actually trigger any alarm in the shopping center once you reach out of the perimeter?

Unlikely as the coil in the street only transmits, there would have to be another bluetooth antenna around for that, but interesting idea.
Also the chance of an employee going off the stores property to attempt to apprehend a cart thief in the act is zero. Its a risk not worth taking.
 

Online Bud

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Re: EEVblog #1287 - Gatekeeper Shopping Trolley Lock Investigated
« Reply #33 on: February 27, 2020, 09:42:15 pm »
Cant wait for Google to bring their facebook- unlocked carts. From their, the possibilities to punish the offenders are endless.
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Offline ve7xen

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Re: EEVblog #1287 - Gatekeeper Shopping Trolley Lock Investigated
« Reply #34 on: February 28, 2020, 12:05:20 am »
The local super markets around here just put knobbly paving at all points of access which makes it extremely hard to push the trolleys any further as the wheels jam and jitter on the knobbly surface cars can drive over it and people can walk on it but the spacing is just right to catch shopping trolley wheels which don't require expensive braking systems or buried coils.

When a new Sainsburys store was built in my hometown in the mid 90s, they put in a system that was a slightly more sophisticated version of this. The trolley wheels didn't have the usual rubber tyre, but instead had two radial flanges as the rolling surface. At all the pedestrian exits, they installed metal plates on the ground that had a longitudinal ribbed pattern, but the ribbing was offset every 6 inches or so, like this:

| | | |
 | | |


This meant it was impossible to push a trolley across, as the wheels would get jammed.

Ingenious, but ultimately didn't work too well, as people just carried the trollies the few feet, or wheeled them through the adjacent patchily-shrubbed areas. :)

The supermarket moved to a locking chain and coin deposit system a few years later.

Interesting. I've never seen this mechanism used for anti-theft, but it is fairly common here for cart-compatible escalators (low slope, with the surface being textured similar to how you describe, the wheels lock up on it).
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Offline grythumn

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Re: EEVblog #1287 - Gatekeeper Shopping Trolley Lock Investigated
« Reply #35 on: February 28, 2020, 09:17:10 pm »
Interesting. I've never seen this mechanism used for anti-theft, but it is fairly common here for cart-compatible escalators (low slope, with the surface being textured similar to how you describe, the wheels lock up on it).

One of the local grocery stores has a step-less escalator to an underground garage, basically a conveyor belt arrangement; the cart's wheels lock when you go down. There are what look like lenses about every 6 inches at wheel level; I assume that's what triggers them.

 


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