Halloween is the time of year when makers add LEDS and sound effects to cheap goodies bought at pound shops and supermarkets.

I saw this skull in my local Asda, and thought it was ideal for a bit of modding. The cranium is quite rigid, and as it’s hollow there’s room to put stuff inside it. I used my Dremel to drill a 3mm hole in each eye socket, and to cut a square out of the bottom to allow access. I threaded orange LEDs through the hole in the base to each eye hole, and secured them in place with a dollop of hot glue, which also gave the LEDs a nice diffuse look inside the eye socket.

The plan was to have the eyes gently puslsing and to make spooky sound effects play as trick-or-treaters approached. I have a PIR detector in my box of bits and so I connected it to a Raspberry Pi and used the examples from the gpiozero documentation to write some code to use the sensor as a trigger. I’d tried using this sensor before for something and couldn’t get it to work, and again it defeated me. I’m sure there’s a trick to setting the sensitivity pot just right on these things, but I couldn’t make it work so chucked it back in the box for another day.

Instead I decided to add a button so the trick-or-treaters can scare themselves by playing the sounds if they’re brave enough! The illuminated arcade button that came as part of the Google AIY kit with issue 57 of the MagPi was perfect!

Sounds are played with a Pimoroni Speaker pHAT (I love these). I got the audio files from a Spooky sounds CD I bought at Woolies years ago. It plays just over an hour of gruesome sounds, and I edited a few short samples from it to use here.

Having got the electronics and software working I made a stand out of plywood, drilled holes for the button and to allow wires to pass through into to skull, and painted this black.

Paint it black

Once the paint was dry I put all the bits together. Having glued the LEDs to the skull earlier I had to take unfasten them now to let me hide the Raspberry Pi underneath the stand. Threading the wires from the Raspberry Pi, through the top of the stand, into the skull and then into the small holes in the eye sockets was tricky, but some patient fiddling about helped me get there. Really this is just a new version of the box of horrors I made at Halloween a couple of years ago, just don’t tell anyone I’m recycling my ideas!