Vol. 25: Secret Knock Gumball Machine

Make a cute candy vending machine that only dispenses treats when you knock the secret rhythm on its front panel.

By Steve Hoefer

Photos by Liz Smith, Steve Hoefer, Garry McLeod

Illustrations by Rob Nance

+ Downloads & Extras:


Secret Knock Gumball Machine on Make: Live

Check out Make: Live, our live-streaming show-and-tell, every 2nd and 4th Wednesday of the month at 9pm ET/6pm PT.

+ Bonus spray paint stencils

Illustrations by Rob Nance

+ Layout/wiring diagram

+ Schematic diagram

+ secret_knock_gumball_machine.pde

+ servo_reset.zip

+ Templates for case

MAKE: AMENDS Errata for This Article


Correction for page 95
Secret-Knock Gumball Machine" (MAKE 25), on page 95, the part number listed for the clear plastic globe from 1000bulbs.com was incorrect and should have read #3202-08020.

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