Christmas themed Microbit adaptation of /mcqn/guard-o-tron3000
You will need a HC-SR501 PIR sensor. See this page for details of how to run the sensor on the 3v3 Microbit power. http://techgurka.blogspot.co.uk/2013/05/cheap-pyroelectric-infrared-pir-motion.html
Also needed are a buzzer, two leds, nine jumper wires and five countersunk M3 nuts (+10 M3 bolts) to connect the Microbit.
Example block code: https://makecode.microbit.org/_YeH7suVvqahh
Full wiring and making instructions coming soon..