There are legions of Ghostbusters cosplayers and even if they all base their outfits on the ones seen in the film, they’re each a little bit different. Instructables user depotdevoid upgraded his to have a functioning Proton pack – well, as functioning as it can be without actually trapping ghosts. He used an Arduino shield that fits into the wand and even though he was a beginner at using microcontrollers, he nailed it. The basics for the light effects:
My simplistic idea for how to make this work does however have the advantage of being both very easy to understand by the uninitiated and very simple to change if you want to alter the way the lights flash.
The basic concept behind the code is that it runs a loop 6.4 seconds long, broken into 64 100 millisecond “ticks.” At each tick, I can have a light turn on, turn off, dim, brighten, etc. After it’s gone through it all once, it goes right back to the beginning and repeats until the battery runs out.