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EEVblog #1334 – Mystery Dumpster Teardown

Mystery dumpster teardown time! With the most amazing mechanical mains power switch you’ll ever see! ...


  1. Kaushlesh Chandel

    Nice… you can make some sort of game for Sagan, with that nice Keypad matrix.

  2. I think that cash drawer is supposed to be like that. The key hole in the front locks the drawer inside the box so if the solenoid activates, it doesn’t pop out. But if the box is unlocked, it’s all fine and dandy that you can manually release the drawer. There’s usually even a button on the keypad to release the cash drawer.

    • The locks on most cash drawers are token efforts, usually use a generic key and most can be opened with a biro lid, dont even have to break the cylinder, some can even be popped open by squeezing the sides hard enough to deform it enough for the lock to disengage, never understood the logic of using flimsy steel in there construction

      • The cash drawer is only a temporary store, which is attended most of the time, once you get significant money in there it usually goes into the safe/bank. I think the security is only designed to protect against opertunists (snatch n grab) not determined criminals. If someone can get at the till and squeze it or poke it with biros you’ve got bigger problems than the till contents

      • It is there to keep the honest people from stealing.

  3. Can we have a VFD reverse engineering video please?!

  4. “The downster dumpstairs” 😉 Nice video Dave, I’ve always wanted to know how those thermal printers worked. If I had to complain about something, I would tell you to swap your screwdriver by the plastic poker, the sound it makes when hits metal and board is a bit annoying with headphones…

  5. Most VFD’s used in vending and POS devices just take raw ASCI sent over serial, sometimes you also have screen brightness line. If you could get your hands on a vending machine or coffee machine that would make a good tear down, as there are some interesting design challenges faced with noisey moters and boiling water, also they are all designed to be field serviceable which would make an interesting discussion point in terms of product design.

    As for the paper trimmer can think of a lot of uses for it:
    – trimming rough edges from 3d prints, kind of like a automated ‘nibbler’
    – kapton tape trimmer
    – precision cable dispenser, add a stepper to unwind a spool set number of steps then sheer
    – ribbon cable sheers
    – bog roll conserver, automatically cut off when you have taken 2 sheets (useful for when you have annoying house guests), just add a rotary encoder to the bog roll holder
    – expired credit card mincer
    – Use the entire thermal printer and build a plotter for an analog multimeter

    • I wouldn’t have guessed ASCII over serial. I expected a bit lower level than that.

      • In vending its useful to be able to display the alpha numeric key combinations i.e. A6, on POS devices its useful for programming prices and calculated offers such as “Buy N get M free” offers etc. displaying errors etc.

        As ASCII correlates to a byte a character its pretty low level, but the main advantage is the availability of modules from many suppliers so its highly unlikely you would ever struggle to obtain compatible spares.

        A lot of the protocols in use such as MDB in vending (http://www.vending.org/technical/MDB_3.0.pdf) mandate the use of ASCII and most peripherals will either send or receive ASCII e.g. if you hook a barcode scanner up to hyper terminal or an RFID reader (used for cashless payments) they will just echo the data back as ASCII, the same is true with most thermal printers operating in epson compatibility mode once suitable control bytes have been sent (http://nicholas.piasecki.name/blog/wp-content/uploads/2009/12/ESC-POS-Programming-Guide.pdf).

        I used to work in the POS/Vending industry, its amazing how low tech the implementations are even on the “high tech POS devices” the touch screens tend to operate over serial as there is a mistrust of USB due to several historical terrible implementations due to fundamental misunderstanding of how duplex comms works…. to the extent where some of the most popular note and coin acceptors which are “usb” are in fact embedded USB to serial converters

  6. In any cash register teardown, my first step would always be opening the drawer. ‘Cause ya never know… 😀

  7. Maybe Dave’s gonna set up a storefront to sell uCurrents 🙂

  8. Ha , now I see why you wanted and extra bench “More clutter of course”

  9. I worked for a POS company for a short while. Most of the units have a drawer release under the register near the back. It makes me laugh when I see a robbery video where the masked guy with a gun is demanding the clerk to open the register when all he needs to do is release it with the push of a finger.

  10. Dave, as a sort of a rating system for your Teardown Tuesday videos, have you considered a bodge counter? I think that would be awesome, it could run down the bottom of the screen in large red letters and silently tick over each time you discover one…

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