This detects, as the title says, when an object crosses a designated finish line first. Handy for when you don’t have a multi-shot, split-second picture-taking device, and you’re having an important or semi-important race. There’s a schematic, tips, and all that included in this project site. Now, technically this is for a pinewood derby, but it can be used in a variety of spaces (oh, dear, delightful reader, you don’t need US to tell you alternative uses! You’re well-versed in DIY-wonderfulness, right?).  

 Finish THIS!

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