Mr Tom's World: Trick or Treat Detector

Detect those pesky kids before they get to the front door. Put it outside to spook the Trick-or Treaters as they walk up to your door. This project is motion activated using a PIR sensor, upon activating the Owl and some cheap LED string lights turn on.

Step 1. Prototyping

I built the circuit on a breadboard to test the idea. I used the PIR sensor and breadboard from the brilliant CamJam EduKit 2. I used transistors to drive the LED’s as the Raspberry Pi GPIO pins cannot supply a lot of current. The code was written in Python using the great GPIO Zero API. I set the Python script to load on start-up.

Breadboard layout

GPIO Connections

GPIO 4 - PIR sensor
GPIO 5 - Owl via driver transistor
GPIO 6 - Bat lights via driver transistor
GPIO 12 - Hand lights via driver transistor
GPIO 17 - Shutdown switch

Step 2. Transferring the circuit onto a PCB

The circuit worked well so I decided to transfer the breadboard prototype onto a more permanent Adafruit Perma-Proto HAT.

Step 3. Building into an enclosure

While looking for suitable enclosures in Poundland I came across a nice plastic pot full of Halloween sweets, having removed the sweets to eat later. I set about cutting some holes in the pot for the PIR sensor and 3.5mm mono jacks. I connected all of the cables and checked that it worked.