EEVblog #1287 - Gatekeeper Shopping Trolley Lock Investigated - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: February 25, 2020, 12:14:11 am
content: Dave's local shopping centre just installed shopping trolleys with electronic locking wheels fro ma company called Gatekeeper System, how does it work?Teardown time!Subscribe on Library:https://lbry.tv/$/invite/@eevblog:7

author: steve30
author_rank: Frequent Contributor
timestamp: February 25, 2020, 01:00:27 am
content: Nice video.I remember starting to see these kinds of things in the 2000s. There used to be a Tesco in the next town which had various signs up telling people their trolleys will stop beyond this point.Here's a photo I took of such a sign back in 2008. I thought this particular one was rather amusing.

author: Stray Electron
author_rank: Super Contributor
timestamp: February 25, 2020, 02:14:00 am
content: The Walmart near me is about 1/8 of a mile from a very large university and the students keep stealing their shopping carts (a trolley is something you ride!) They tried the locking wheels but gave up. Supposedly, the students were running with them and theyclaimedthat when the wheels locked up the carts would flip and send the students flying in the air and they were getting injured from the fall and threatened to sue Walmart.Yeah, another piece of the growing legal idiocracy in the US.

author: Muttley Snickers
author_rank: Unknown
timestamp: February 25, 2020, 02:49:34 am
content: The system does appear to work, the local Coles has wheel lockable trolleys and I've never seen one of theirs outside the carpark perimeter, plenty of Aldi trolleys around the neighbourhood though. I really wished they also incorporated a permanent brake so people would have to hold a lever to release the wheel lock, of course they would also need to incorporate an override for the trolley collectors as well.An example of somebodys blatant stupidity below.https://www.ozbargain.com.au/node/440923

author: EEVblog
author_rank: Unknown
timestamp: February 25, 2020, 03:12:07 am
content: Quote from: Muttley Snickers on February 25, 2020, 02:49:34 amMy shopping centre only has Coles and there are dozens of trolleys littered outside the carpark. Doesn't seem to work here.

author: jhalar
author_rank: Regular Contributor
timestamp: February 25, 2020, 04:27:37 am
content: I've seen a trolley with the lock wheel being pushed through the streets outside of my local Sydney shopping centre.Two people lifting the wheel off the ground while one person was pushing the trolley.I thought that all three of them could have carried the shopping bags easily.

author: johnlsenchak
author_rank: Frequent Contributor
timestamp: February 25, 2020, 04:37:42 am
content: My original thought before you cracked that the wheel open, is that the it would spin turning the DC motor which then would charge the battery as the shopping cart (trolley) was used on a daily basis going up and down the aisles in the store.

author: JustMeHere
author_rank: Frequent Contributor
timestamp: February 25, 2020, 07:58:01 am
content: Quote from: EEVblog on February 25, 2020, 03:12:07 amMaybe they are outside of the car park because the wheels locked up and were left.I wonder if you can open them with heat.

author: ogden
author_rank: Super Contributor
timestamp: February 25, 2020, 06:23:43 pm
content: 2.4 GHz radio could be beacon for direction-finding

author: nctnico
author_rank: Super Contributor
timestamp: February 25, 2020, 08:25:30 pm
content: Quote from: steve30 on February 25, 2020, 01:00:27 amI think I've seen them over here (in the NL) too but all shops have trolleys which are chained together and you need a coin to unlock a trolley nowadays.

author: Stray Electron
author_rank: Super Contributor
timestamp: February 25, 2020, 08:44:34 pm
content: We have a few of those too but you'd be surprised how many people (including the ones that don't take them out of the store parking lot) won't return them to the rack and get their quarter (1/4 of a dollar) back.

author: james_s
author_rank: Super Contributor
timestamp: February 25, 2020, 08:56:14 pm
content: They should put a fully refundable fee of a few dollars on the cart to get people to return it, I hate it when I'm trying to park and there are shopping carts randomly scattered around the parking lot, people are so lazy.I didn't realize carts were $500+, that's pushing up on felony theft territory. Maybe if they started prosecuting a few people others would get the message.

author: ogden
author_rank: Super Contributor
timestamp: February 25, 2020, 09:18:58 pm
content: Quote from: james_s on February 25, 2020, 08:56:14 pmIt works very well for a lot less money. When lazy leaves cart, poor or just kids will return it to get a coin.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: February 25, 2020, 09:48:20 pm
content: Quote from: james_s on February 25, 2020, 08:56:14 pmThey aren't. That figure came from reports of trolleys full of goods being stolen, not the trolley

author: thm_w
author_rank: Super Contributor
timestamp: February 25, 2020, 09:58:02 pm
content: Quote from: Stray Electron on February 25, 2020, 08:44:34 pmIts $1 here, I think no one cares about 25c now. Too bad $1 coins in USA are relatively rare otherwise they'd switch to that.

author: nctnico
author_rank: Super Contributor
timestamp: February 25, 2020, 09:58:26 pm
content: Quote from: mikeselectricstuff on February 25, 2020, 09:48:20 pmTrolleys are rather expensive. Not $500 but not much less either. It seems $200 is the low mark.

author: magic
author_rank: Super Contributor
timestamp: February 25, 2020, 10:20:40 pm
content: In related news, I had never seen a supermarket trolley outside the supermarket's parking lot until I went to America

author: Cerebus
author_rank: Super Contributor
timestamp: February 26, 2020, 12:05:57 am
content: Quote from: ogden on February 25, 2020, 06:23:43 pmDirection finding so that the trolley can steer itself any direction except the one you want it to go?

author: Mr.B
author_rank: Unknown
timestamp: February 26, 2020, 12:24:39 am
content: Quote from: Cerebus on February 26, 2020, 12:05:57 amI thought the low tech models already did this.They all do at my local supermarket...

author: texaspyro
author_rank: Super Contributor
timestamp: February 26, 2020, 03:00:34 am
content: I saw a fully mechanical version of these. They buried strong Nd magnets in the pavement that interacted with a magnet on a locking latch on the cart. Cross the magnetic barrier and the wheels lock. It took a special tool to unlock the wheels.

author: Gary350z
author_rank: Regular Contributor
timestamp: February 26, 2020, 05:32:59 am
content: I was looking at these a while back. Here is some more information.How it works:Anti-Theft Device Keeps Shopping Carts on the Job - Science Channelhttps://youtu.be/PWZOeM5jdjg?t=71Teardown:The Wheel Locking Wheel Teardown - The Workbenchhttps://youtu.be/XMHzb5S7X04How to hack the system and lock all the carts at the same time:EMP Shopping Cart Locker - Instructableshttps://www.instructables.com/id/EMP-shopping-cart-locker/

author: G7PSK
author_rank: Super Contributor
timestamp: February 26, 2020, 02:26:29 pm
content: 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. The other thing the often have is requirement for a coin or token to unchain the trolley, seems a pound is worth more to most people than a \shopping trolley.

author: ogden
author_rank: Super Contributor
timestamp: February 26, 2020, 10:39:12 pm
content: Quote from: Cerebus on February 26, 2020, 12:05:57 amTo steer in any direction you don't need direction finding. Just steer.

author: thm_w
author_rank: Super Contributor
timestamp: February 26, 2020, 10:59:34 pm
content: Quote from: texaspyro on February 26, 2020, 03:00:34 amThats what I had always assumed, it was a simpler mechanical brake. But then, wouldn't that area get filled with ferrous debris?Also if the magnets were strong enough, could potentially trip someone with unusually thick metal shoes or cane. So they can't be too powerful.

author: Maxlor
author_rank: Frequent Contributor
timestamp: February 27, 2020, 12:09:54 am
content: 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? Also the installation pictures show just a burried cable (multi-wire actually, so how does that work? Wouldn't the fields cancel out?), so maybe using a speaker instead of a wire with enough current running through it isn't optimal?Now, if I wanted to generate a signal with all 256 patterns, I'd probably write a program to generate a wave file.. But you have access to fancy function generators. Maybe use this opportunity to demonstrate how they can generate this signal with very little effort? I mean, you keep saying every so often that that part of the value of good test gear is that it saves time.

author: texaspyro
author_rank: Super Contributor
timestamp: February 27, 2020, 01:16:55 am
content: Quote from: thm_w on February 26, 2020, 10:59:34 pmI seem to remember that they collected bottle caps and nails. Nails spread across parking lot exits are not a good thing.

author: amyk
author_rank: Super Contributor
timestamp: February 27, 2020, 02:37:52 am
content: Quote from: JustMeHere on February 25, 2020, 07:58:01 amIf you don't care about them surviving, yes...

author: magic
author_rank: Super Contributor
timestamp: February 27, 2020, 07:29:16 am
content: Quote from: Maxlor on February 27, 2020, 12:09:54 amThat 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.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: February 27, 2020, 08:18:30 am
content: 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

author: HwAoRrDk
author_rank: Super Contributor
timestamp: February 27, 2020, 11:28:48 am
content: Quote from: G7PSK on February 26, 2020, 02:26:29 pmWhen 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.

author: jancelot
author_rank: Regular Contributor
timestamp: February 27, 2020, 08:53:35 pm
content: That in-wheel mechanism is supposed to prevent a trolley/cart from being stolen just locking one wheel? Hilarious nonetheless.

author: jancelot
author_rank: Regular Contributor
timestamp: February 27, 2020, 08:54:46 pm
content: Does that actually trigger any alarm in the shopping center once you reach out of the perimeter?

author: thm_w
author_rank: Super Contributor
timestamp: February 27, 2020, 09:34:14 pm
content: Quote from: jancelot on February 27, 2020, 08:53:35 pmMakes 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.Quote from: jancelot on February 27, 2020, 08:54:46 pmUnlikely 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 goingoffthe stores property to attempt to apprehend a cart thief in the act is zero. Its a risk not worth taking.

author: Bud
author_rank: Super Contributor
timestamp: February 27, 2020, 09:42:15 pm
content: Cant wait for Google to bring their facebook- unlocked carts. From their, the possibilities to punish the offenders are endless.

author: ve7xen
author_rank: Super Contributor
timestamp: February 28, 2020, 12:05:20 am
content: Quote from: HwAoRrDk on February 27, 2020, 11:28:48 amInteresting. 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).

author: grythumn
author_rank: Contributor
timestamp: February 28, 2020, 09:17:10 pm
content: Quote from: ve7xen on February 28, 2020, 12:05:20 amOne 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.