I had it happen at various frequencies and amplitudes. I could basically only control how fast it happened. It also happened in a flat bottomed cup (with a reduced load of sand).
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My bet is it’s the physics of the cup shape. Get a straight walled beaker?
Yeah, the flat bottomed cup that I used was straight walled. It was just me trying the 3d printed cup again, but with less material.
Wanna See?
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Have you tried just a basic exciter?
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My coworker used these and those large foam insulation boards to make some speakers for the assembly line area at my old job. Sounded surprising good, and loud
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Not really. Wanted to prove the idea before putting cash in it. Also just found out I’m strung out for cash till at least the end of the year. 
I did look into the bass shakers that video game racers are using for haptic feedback. I determined that because they work kind bass ackwards 
, they’d be less useable. A subwoofer has a fixed (heavy) magnet, and a moving electromagnetic coil. If I’m gonna add a bunch of mass (sand) then I need the moving parts as light as possible. The bass Shakers / Buttkickers / haptic feedbacks use a fixed coil and a moving mass to create the rumble. If I could get this working, I’d probably try to scale up using a cheap 10-12" sub from a car audio system, and scrap everything except the magnet and coil. Then build on to that.
For now…
I’m exploring using interrupted sound, or sounds that sweep through hz, or randomish hz changes every 1/3 second to try and break up the harmonics. I may also try using containers with not-smooth periphery design (12 point star) and some internal pillars or something. Just try to break up whatever is happening.
Maybe late this week though, I got a buddy’s truck down in my driveway and need to get it mobile again.
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Those who love the 
, understand. Those who do not, never will. 
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I’ll never understand rocks then… Although extracting useful materials out of the rocks is pretty cool IMHO.
Still, steel is more interesting than the rocks it comes from in my boring book.
This might be worth looking into:
Maybe tuning the dimensions so that only the heavier particles end up at the bottom?
I’m not sure if I’m on the right track tho… Gotta look into it when time allows…
Thanks for the range and time info @tac0s !
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Hear ye, hear ye, today I ask with great thanks in advance for observing my riddle;
Particularly in reference to access control, though absolutely extending past that (ie end users using work badges to do non-access-control things, perhaps file access), is there any notable security benefit to DESFire EV3 over EV2?
(This ties into my professional life so I’d like to keep stuff vague past this. I will be doing additional research myself before decisions are made of course, though I figured I would utilize this community for baseline knowledge.)
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There’s only two things. A transaction timer lets the card enforce a max transaction duration to help with MitM linger attacks. That’s not likely to be much of a big deal for end users, but EV3 also supports secure dynamic messaging which is CMAC-authenticated data you can embed in a standard NDEF read.
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Okay, so if one or both of those features are properly implemented by the manufacturer as part of any transactions that would reasonably take place between a badge and a reader in question, then the difference is notable. Otherwise they function closely enough that the difference is negligible.
Thank you for the starting point!
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For access control the timer is the most likely to be implemented. The reason behind this feature has to do with attacks on the Netherlands transit system, and NXP is a Dutch company.. so it was somewhat embarrassing.. but your typical access control systems will just use a secure file and keys to ensure cryptographic security.
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__ __
| |_| |______ _,___ _,___ _ _ \--/
| _ |__ | __ | __ | |_| | /`-' '-`\
|__| |__|__-_,_| ,___| ,___|___, | / \
|_| |_| |_| /.'|/\ /\|'.\
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| |_| |______| | |______ __ _ __ ______ ______ _,____
| _ |__ | | | __ | | | | --__| --__| __ \
|__| |__|__-_,_|_|_|______|_______|______|______|_| |_|
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Free implant!
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