@nugger @Hando So we want a system that basically only goes when you're actively pedaling and only assists when your pedaling is too high of torque? Hall effect sensors measure magnetic field, so they could be used to tell ∆τ (torque) with variation from environment (temp affects them a lot, vibration some). Basically allow the bike to let you pedal a bit harder at the 3-5% incline but when torque goes way up (e.g. 8%) kick on the motor so you don't struggle as much charging the hill. Hall effect sensors can be super light weight and aren't too expensive but a "computer" (PCB?) has to do some calculating to decide when to kick on. Not a huge deal since it would be small. They're cheap too at under $50 most likely.