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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. Actually, I believe the reader is looking for slight changes to the impedance caused by the card shorting the coil.

    Basically the reader emits a monitored 125kHz signal, and when a card is brought near, the change in the impedance of the sending coil is noted for a card presence. Then when the IC is powered up and transmitting, it shorts the coil, which cauess a marked change in the sending coil’s impedance (the two coils work like a transformer, so shorting the secondary end causes the primary to see a short as well as the transformer is also an impedance transforming device).

    It’s backscatter because the impedance change can be detected by other cards (and is used as a collision detection mechanism – if multiple cards are brought to it, the collision is detected when the card doesn’t short the coil, but detects that the coil impedance has been altered, which means the card should wait until the next read cycle. After successfully transmitting, the card shuts down to allow other cards to be identified).

  2. lol @ the DaveCAD I think its funny!

  3. Please Dave, say some words in your next blog regarding the fires around Sydney. Are you or your house affected by these fires laid by some stupid youngsters, as mentioned in our news in Germany?

  4. Hi Dave,

    No need to burn the fire, just put an aspirin on the table, put the wire on the aspirin, get some solder on the tip of you iron, then press the tip on the wire. The aspirin underneath start to melt (avoid the nasty smoke/smell) and the enamel is replaced with a nice and shiny solder. Now you can join the two wires.

    The same tip a gave to the folks from TheBackShed forums. Tell me how it works.


  5. Fantastic blog! Do you have any tips and hintsfor aspiring writers? I’m planning to startmy own site soon but I’m a little lost on everything. Would you advise starting with afree platform like WordPress or go for a paid option? There are so many optionsout there that I’m completely overwhelmed .. Any suggestions?Appreciate it!

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