Piecax the Poltergeist reinvents the Knock Block


[AndyGadget] built a haunted box as part of his Halloween preparations. This follows in the footsteps of the Knock Block we saw earlier this month but makes several hardware changes. He’s replaced the solenoid with a DC motor that rotates an arm to do the knocking. He’s avoided any CNC work by using a softwood box from a craft store as the enclosure. For control circuitry he’s used an 8-pin PICAXE Microcontroller that ‘listens’ for knocking on the box via a piezo buzzer. It will mimic knocks back to you, and if it hears the right combination The Addams Family theme song is played. This useless machine will make a great office conversation piece and with this simplified design it’s much easier to build than the Knock Block. See it perform after the break.


  1. Mike D. says:

    Nice work.

  2. polymath says:

    The Adam’s family was a nice touch.

  3. Concino says:


  4. japkin says:

    That’s awesome.

  5. Stefan says:

    Fantastic work.
    Wanna have one! :D

  6. Carl says:

    Sometimes the smallest things can bring the biggest smiles.

    Great little project.

  7. Stu says:

    Cool design, made me larff when it did the knocks thru the addams family song.
    One little thing tho – the wristwatch beep sound kind of ruins the effect doesn’t it? I wonder if an ISD chipcorder would sound less corny.

  8. SchrodingersCat says:


  9. bill hates says:

    truely awesome

  10. PocketBrain says:

    Hey! When you do “shave and a haircut” HE oughta do “two bits!”

  11. maxpowa says:

    100% hack

  12. Farris says:

    Kinda timely, considering the writer of the Addams Family theme song (and the Green Acres theme song) just passed away like a week ago. I heard it on Bob and Tom.

  13. sl says:

    I think it would be even better if, rather than playing the whole theme with a beeper like that, it plays the song just as beats with the solenoid. When it gets to the bridge, it wouldn’t continue until you provide it with the two taps. Much more interactive

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