The Scare-O-Matic is a little box 105mm x 65mm x 45mm with a 5V barrel jack for power supply, a motion sensor and a powerful 0.5W 45mm diameter speaker.
The motion sensor is wired to a Sparkfun microSD Audio Module WTV020SD to trigger the next sound clip when motion is detected. The full circuit schematic is shown here:
Everything is held together nicely with hot glue and double sided tape in a Hammond Box with holes for the barrel jack, the motion sensor and the speaker.
Details
The audio module requires audio files in 4-bit ADPCM (.ad4) file format. There is a converter utility on the Sparkfun product page. I found that not all WAV files that I converted were able to play, so I just tried a lot until I had a big enough number of files to make it not repeat itself too quickly. A ZIP of all the files I used is located here:
https://cdn.hackaday.io/files/3238138534592/SDCard.zip
On the audio board when the 'next' signal goes active, the current clip is stopped and the next one is played. This did not work very well with the motion sensor, which outputs a lot of pulses when active. To finish every sound clip and wait for the next pulse, the motion signal was or'ed together with the busy signal from the sound module and connected to the 'next clip' input. This guaranteed to finish playing the current track before the next track is played. this is how it looks inside the box:
I added a video that demonstrates all the scary sound clips:
The only thing that is missing now is a scary paint job, but instead I have put a big googly eye on it, as can be seen in the video.
Parts List:
| 1 | × | Sparkfun WTV020SD microSD Audio Module |
| 1 | × | 5mm x 2.1mm Barrel Jack connector |
| 1 | × | 0.5W Speaker JS-5050-I8 |
| 1 | × | Panasonic EKMB1101112 Motion Sensor |
| 1 | × | Hammond 1594 Box |
| 1 | × | 1GB MicroSD card |
| 1 | × | Googly Eye |
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