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.
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.