Put an End to Stockings Full of Coal with the Raspberry Pi Santa Detector

December 21, 2018 by Robin Mitchell

For most, the name "Father Christmas" conjures images of toys and gadgets. But for this gentleman maker, the name brings misery. Be sure to stockpile your Arduino, Raspberry Pi, and Particle Photons; it's time to catch Saint Nick red-handed.

For most, the name "Father Christmas" conjures images of toys and gadgets. But for this gentleman maker, the name brings misery. Be sure to stockpile your Arduino, Raspberry Pi, and Particle Photons; it's time to catch Saint Nick red-handed.

It’s that time of year again. The man in red will be showing up to once again deliver coal to many thousands of people. In this episode of the Gentleman Maker, we will create the Santa Detector, a system that will allow us to monitor, photograph, and even fight back against the so-called jolly man and finally bring justice to those left disappointed at this time of year!

While there are many people out there who wake up on Christmas morning to find their stockings full of gifts, I often find mine full of coal and can never understand why. I work hard, pay my taxes, and even used to leave carrots out for his reindeer, but it would seem that no matter how much I try or bribe, Santa won’t budge.

I don’t know about you, but a man who knows when you’re sleeping and climbs into your room in the middle of the night is something that just does not sit right with me! Well, Santa has clearly never met an engineer armed with modern technology, so we will use maker equipment to try and capture footage of him, as well as create an alarm system that will alert me to his presence!

Santa Detector BOM

  • 3 x 10K resistors
  • 5 x 100nF capacitors
  • 2 x Potentiometers (value not entirely important)
  • 1 x 1N5817 diode
  • 2 x 555 timers
  • 1 x LM358
  • 1 x Piezo disc
  • 1 x Electret microphone
  • 1 x Buzzer (loud 5V piezo-based alarm)
  • 1 x Photon relay shield
  • 2 x Particle Photons
  • Mains lights and wire
  • 1 x Arduino
  • 1 x Raspberry Pi
  • 1 x Microphone and USB sound card
  • 1 x USB webcam
  • 1 x Speaker and supporting hardware
  • 1 x Ultrasonic module
  • Circuit construction equipment

The Schematic



The Santa Detector has three separate circuits to construct, all of which you can get a better look at above. To check out the full schematic, be sure to visit Scheme-It.

Detection Systems

This project combines multiple projects:

The project also includes the following circuits:

  • Piezo sensors mounted to the roof are used to detect a landing using a simple op-amp comparator.
  • An internal microphone is used to detect jingles and is connected to a comparator.
  • Both of the above are connected to a 555 monostable that is connected to a Particle Photon.
  • Both of the above are connected to Particle Photon.


The First Line of Defense: Piezo Disc Detectors

The first line of detectors is a piezo disc that is mounted to the underside of the roof and is used to detect the impact of a sleigh and reindeer feet. This disc is connected to a simple comparator circuit, which is also connected to a 555 monostable circuit that is used to produce an extended pulse upon detecting the sleigh. This extended pulse gives the Particle Photon time to react to the change in input signal, and upon detection, it will update an online counter found on Adafruit IO. An electret microphone is also used to detect the sound of jingle bells, which is also connected to a comparator and 555 monostable for detection by the Photon.

The Second Line of Defense: Ultrasonic Motion Detector

The second line of detection is done using an ultrasonic motion detector, which constantly scans the top of the roof for the presence of any men in red with large four-legged animals. This ultrasonic module is connected to an Arduino Uno, which is then connected to a Raspberry Pi. If a reading from the ultrasonic module falls below a certain value, the Arduino sends a message to the Pi over a UART port.

The Final Line of Defense: Speech Recognition

The third line of detection uses speech recognition that is executed upon the detection of all previous sensors. The speech recognition system, upon activation, looks for keywords including “Ho Ho Ho”, “Merry Christmas”, and “Rudolph”. When a keyword has been found, the system starts by signaling the alarms and begins taking pictures with the USB webcam. At this time, the Photon relay shield receives the alarm request and starts by turning on bright floodlights that allow the camera to take photographs easily, while also sounding a buzzer and blinking red bulbs to alert security of the breach in the perimeter.

The Code

There are multiple pieces of code used to run this project, including code for the Photon, which can be found on Particle IO. The rest of the code required for this project can be downloaded below.


Are you ready to catch Santa this year? With our combined efforts, perhaps we can rid the world of stockings full of coal once and for all.



With all your spare time this holiday season, why not indulge in more of the Gentleman Maker? Check out all of the previous installments below:

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