SFX - Matilda - Chalkboard

For the spring production of Matilda the Musical at my daughter's high school I created the chalkboard which would need to show writing at a key point in a song. A spare flat-screen TV was tested and used for the display rather than a system of real chalk and magnets, just to ensure the effect could be triggered reliably during each show. This was only made possible by the video already shared by Spencer Bawden for the same effect: • Matilda Chalkboard Scene
The prop itself was mostly a wooden frame for the TV and I designed it to look like an old school chalkboard, as it needed to be stable and easily moved on casters. The video was played on demand by using a Raspberry Pi, some momentary switches, and use of the GPIO pins to start or stop the video which was played using VLC. A small monitor attached to the back of the display allowed the prop operator to know precisely when the effect was started. A piece of 1/4" plexiglass was used on the front, which was sprayed black around the edges on the backside, while the front got a coating of matte clear protectant and sponged with black paint to help blend out the edges of the TV mounted behind. This allowed it to be used as a real chalkboard throughout the performance, and simply wiped down during intermission in preparation for the final effect to play.