ScaleSync is an Arduino-based speed detection device I built to help model railroaders like myself easily measure train speeds. It uses two infrared sensors to calculate how fast a train is moving as it passes through a track section. It’s super easy to use, runs on two AA batteries or usb mini, and works for multiple scales. You can use it to speed match DCC locos, dial in scale miles per hour for realistic operations, or even check speeds on DC setups. I designed it to fit over NMRA double track spacing for N scale and it also handles HO scale intermodal double-stack trains without a problem. Whether you're building a prototypical layout or just want your engines running consistently, ScaleSync makes it easy to see what your trains are really doing.