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- 419 Comments
Ulvainto Showerthoughts@lemmy.world•I wonder what the specs are on the technology that disables shopping cart wheels722·10 days agoThis might actually be a good opportunity for an AI answer:
–
First, understand the basic principle you’re working with:
Shopping cart wheel locks respond to a specific RF (radio frequency) signal (typically around 7.8 kHz to 10 kHz for many systems, but it varies by brand).
In normal operation, the boundary wire emits this signal constantly.
The unlocking posts emit a different coded signal to reset the wheel.
So to design a portable device that could lock and unlock wheels manually anywhere, you would need:
- Identify the Signals
You must figure out the exact frequencies and modulation patterns used by the cart system.
Different companies (like Gatekeeper Systems, Carttronics, etc.) use slightly different RF signatures.
Usually lock signal = basic broadcast (constant tone) Unlock signal = special modulated unlock code or sequence.
This might require:
A spectrum analyzer
Or reverse-engineering an existing unlock station.
- Design the Portable Emitter
The portable device needs:
A programmable low-frequency RF transmitter (around 8–10 kHz range, low power)
A microcontroller (Arduino, ESP32, etc.) to generate the right modulation if the signal is coded
An amplifier to make the signal strong enough to reach the cart wheels (they usually detect it within 3–10 feet)
Optionally:
Two modes: a “lock” mode (sending the boundary signal) and an “unlock” mode (sending the unlock code).
- Basic Hardware Components
Low-frequency oscillator (to generate 7.8–10 kHz wave)
Microcontroller (to handle switching, coding)
Coil antenna (for strong near-field transmission — like a small induction coil)
Amplifier circuit (boost the signal so carts sense it a few meters away)
Battery pack (portable, rechargeable — say 12V lithium-ion)
Mode selector switch (Lock / Unlock)
- Software
Simple microcontroller code to:
Emit plain carrier signal = Lock mode
Emit modulated code = Unlock mode
Example (pseudo-Arduino code):
if (mode == LOCK) { generateContinuousTone(8kHz); } else if (mode == UNLOCK) { generateUnlockCode(); }
- Important Challenges
Matching signal format exactly: If the unlock signal is digitally modulated (like FSK or ASK), you must match the timing perfectly.
Power levels: Too much power could fry circuits or interfere with nearby electronics. Keeping it safe is key.
Legal considerations: Broadcasting radio signals, even low-power ones, can be restricted depending on the country.
Simple Concept Sketch:
[Portable RF Cart Lock/Unlock Device]
Size: About a large walkie-talkie
Two buttons: Lock / Unlock
Coil antenna: About 3–6 inches
Range: 1–3 meters effective
Display: Small LED indicators (Locking / Unlocking / Signal OK)
In short: You’re essentially building a portable invisible “fence” generator with two channels: a “keep away” signal (lock) and a “come back” signal (unlock).
Ulvainto News@lemmy.world•Slate Truck is a $20,000 American-made electric pickup with no paint, no stereo, and no touchscreen1·10 days agoInteresting thank you! Not yet the tiny no bells no whistles electric pickup I’m hoping for, but it’s nice to see Canadian alternatives for things i didn’t know we did!
I would add something about the minimum “decent roommate” amount of maintenance that the paying roommate still has to do, to avoid them gradually becoming more and more of an intentional slob, and treating the cleaning roommate like a servant
Ulvainto News@lemmy.world•Slate Truck is a $20,000 American-made electric pickup with no paint, no stereo, and no touchscreen111·13 days agoMy exact thought! I wish a Canadian startup did exactly that, I’d buy one immediately
Ulvainto politics @lemmy.world•A Loophole That Would Swallow the Constitution | If Donald Trump can disappear people to El Salvador without due process, he can do anything.4·21 days agoRight? I mean hindsight is 20/20 and all that, but come on…
Now it means technically you’d need some kind of shared enforcement accountability - but how to make any congress-controlled or judicial-controlled enforcement group big enough to compete with the US army when push comes to shove… 🤷♂️
Ulvainto politics @lemmy.world•A Loophole That Would Swallow the Constitution | If Donald Trump can disappear people to El Salvador without due process, he can do anything.23·21 days agoAll forces of enforcement of laws being created by one branch or interpreted by another being basically under the third, which incidentally is the one branch with an all powerful executive means the whole checks and balances was flawed from the get go, and assumed way too much good faith leadership, IMO
Ulvainto Ukraine@sopuli.xyz•Trump Keeps Falsely Claiming Ukraine Started the War With Russia15·23 days ago“well everyone knows, you go out dressed like that, Russia will invade you. It’s your fault, it’s common sense”
Ulvainto Tycoon Games@lemmy.world•Sintopia, a hell city-builder/management game x evil god game hybrid (with an independent overworld where you can cast spells), releases demo on SteamEnglish3·1 month agoThe description reminds me of the old dos game populous
Sometimes - rarely but sometimes - AI image generation does good for the world.
Ulvainto Europe@feddit.org•Top French court rules political bans are legal, delivering blow to Le PenEnglish1·1 month agoYeah, put a cap on Le Pen
Ulvainto Canada@lemmy.ca•Danielle Smith and Ben Shapiro discuss Canada electing ‘solid allies’ to Trump at Florida event6·1 month agoI think Mark Carney should call her out loudly and publicly for being unCanadian
Ulvainto Canada@lemmy.ca•Danielle Smith and Ben Shapiro discuss Canada electing ‘solid allies’ to Trump at Florida event3·1 month ago“could”?!!?!?
“in a move that infuriates conservatives…”