Halloween Door Knocker

Door knockerBackside preparation_labeled

In 2013, a guy named Chuck was featured on Hackaday.com. His project was to animate a cheap plastic Halloween door knocker with a servo and some LEDs. I thought I’d take a swing at this project, adding motion sensing and a customize-able sound that you can record with the attached microphone. Here’s my version:

spice shaker lid
This spice shaker lid worked great for making an armature that is allowed to slip.
Transistor for High power LEDs
I soldered a resistor to the base of the TIP31 transistor, and wired the two high powered LEDs in series.
IMG_0149
Back of the door knocker project showing the arduino, battery pack, capacitor bank, and on/off switch.

 

Parts List:

  1. Door knocker on Amazon
  2. Arduino compatible microcontroller (I used an Arduino Pro Mini, Chuck used a Digispark)
  3. On/off switch
  4. 4xAA Battery Pack + small piece of Velcro
  5. PIR motion sensor
  6. Servo (I used a continuous rotation servo, Chuck used a regular one)
  7. LEDs with appropriate resistors
  8. Transistor or MOSFET to fade the eyes on/off (I used a TIP31C)
  9. Sound recorder from a greeting card (also available on eBay)
  10. Solder & hot glue to hold things together

I also added a pair of electrolytic capacitors in parallel with the power supply. Before the capacitors were installed, I was having trouble with the arduino losing power due to the voltage drop when the servo starts moving.

 

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